Research Items (110)
Background Several rating scales assessing stress-related symptoms of exhaustion have emerged in recent years. However, more knowledge is needed about the performance of these rating scales in patients with stress-related disorders as well as in other patient groups. With the recently developed Karolinska Exhaustion Disorder Scale (KEDS), we compared symptoms of exhaustion in different patient groups that were sorted according to diagnosis. Methods Patients were sampled consecutively from departments of occupational medicine (DOM) at three Danish hospitals. The total study group comprised 698 care-seeking patients (487 women). Patients with stress-related diagnoses (n = 217; the International Classification of Diseases [ICD]-10 code F43: reaction to severe stress and adjustment disorder) were compared to a diverse group of patients with a range of somatic diagnoses (n = 338) and to patients with other psychiatric diagnoses (n = 143), including subgroups with major depression disorder (n = 34; F32 and F33) and problems related to employment and unemployment (n = 99; Z56). The data were analysed using linear mixed models with the SPSS statistical program. Results The mean KEDS sum score in patients with stress-related diagnoses (29.3; SD = 8.0) was significantly higher than in patients with other psychiatric diagnoses (25.9; SD = 9.5) and in patients with somatic diagnoses (17.6; SD = 10.8). The subgroup with a major depression disorder had high mean KEDS sum scores (31.4, SD = 8.1), similar to patients with stress-related diagnoses, while the mean KEDS sum score in patients with problems related to employment and unemployment (Z56) was 23.5 (SD = 9.0). Young and old patients scored similarly on KEDS, but in patients with somatic diagnoses, female patients scored significantly higher than male patients. Conclusion The symptoms of exhaustion measured with KEDS were higher in patients with stress-related diagnoses and major depression disorder than in patients with somatic diagnoses. The intermediate level of the symptoms of exhaustion that were associated with problems related to employment and unemployment, (Z56) compared to the lower level of the symptoms with somatic diagnoses, suggests that KEDS might be useful in detecting mild, prodromal states of exhaustion. This needs further investigation.
Background: The prevention and rehabilitation of multisite musculoskeletal pain would benefit from studies aiming to understand its underlying mechanism. Autonomic imbalance is a suggested mechanism for multisite pain, but hardly been studied during normal daily living. Therefore, the aim of the study is to investigate the association between multisite musculoskeletal pain and cardiac autonomic modulation during work, leisure and sleep. Methods: This study is based on data from the "Danish Physical activity cohort with objective measurements" among 568 blue-collar workers. Pain intensity scales were dichotomized according to the median of each scale, and the number of pain sites was calculated. No site was regarded as the pain-free, one site was considered as single-site musculoskeletal pain and pain in two or more sites was regarded as multisite musculoskeletal pain. Heart rate variability (HRV) was measured by an electrocardiogram system (ActiHeart) and physical activity using accelerometers (Actigraph). Crude and adjusted linear mixed models were applied to investigate the association between groups and cardiac autonomic regulation during work, leisure and sleep. Results: There was no significant difference between groups and no significant interaction between groups and domains in the crude or adjusted models for any HRV index. Significant differences between domains were found in the crude and adjusted model for all indices, except SDNN; sleep time showed higher values than leisure and work time, except for LF and LF/HF, which were higher during work. Conclusion: This cross-sectional study showed that multisite musculoskeletal pain is not associated with imbalanced cardiac autonomic regulation during work, leisure and sleep time.
PurposeThe differential effect of occupational and leisure time physical activity on cardiovascular health is termed the physical activity health paradox. Cardiac autonomic modulation could bring insights about the underlying mechanism behind this differential effect. The aim was to compare heart rate variability (HRV) during different activities (sitting, standing and moving) at work and leisure among blue-collar workers. Methods One hundred thirty-eight workers from the NOMAD cohort were included. Data from physical activity and HRV were obtained for 3–4 days using tri-axial accelerometers (Actigraph GT3X+) and a heart rate monitor (Actiheart). HRV indices were determined during sitting, standing and moving both at work and leisure. Linear mixed-models with two fixed factors (activities and domains) were applied to investigate differences in HRV indices adjusting for individual and occupational factors. ResultsThe results showed significant effects of domain (p < 0.01), physical activity type (p < 0.01) and interaction between domain and activity type (p < 0.01) on HRV indices. Mean heart rate (IBI) and parasympathetic measures of HRV (RMSSD and HF) were lower for sitting (p < 0.01) and higher for moving (p < 0.01) during work compared with leisure, while no difference between domains was found for standing (p > 0.05). Sympathovagal balance (LF/HF) was higher during work for sitting and moving (p < 0.01), but showed no difference for standing (p = 0.62). Conclusions Differences in cardiac autonomic modulation between work and leisure were found, indicating sympathetic predominance during work and parasympathetic predominance during leisure for sitting. Autonomic responses can be part of the mechanism that explains the differential effect of occupational and leisure time physical activity on health.
- Aug 2017
- Eliminating Occupational Disease: Translating Research into Action, EPICOH 2017, EPICOH 2017, 28–31 August 2017, Edinburgh, UK
Background Long-term environmental noise exposure has repeatedly been related to increased risk of cardiovascular disease at exposure levels as low as 35 dB(A). Occupational exposure levels are orders of magnitude higher than the environmental levels. We examined if blood pressure was increased during and subsequent to occupational noise exposure. Methods We studied 483 industrial, finance, and service workers selected as a random sample from 10 industrial trades and financial services between 2009 and 2010. For 24 hours, we recorded noise exposure levels every 5 s by personal dosimeters and measured ambulatory blood pressure and heart rate every 20–30 min. In mixed linear regression models, we assessed the acute and lagged effects of ambient noise exposure (LAEq)) on blood pressure and heart rate for work, leisure and night hours. For 319 workers, we estimated these effects for noise exposure at the ear accounting for hearing protection use. Results Full-shift occupational noise exposure levels ranged between 59–97 dB(A). Results of the regression models adjusted for sex, age, income, BMI, alcohol, tobacco, salt intake, and family history of hypertension suggest no relation between acute or lagged occupational noise exposure level and blood pressure levels for the industrial workers. Conclusion Occupational noise exposure showed no acute or lagged effects on blood pressure in industrial workers.
- Mar 2017
Aims To survey current, Danish industrial noise levels and the use of hearing protection devices (HPD) over a 10-year period and to characterise the association between occupational noise and hearing threshold shift in the same period. Furthermore, the risk of hearing loss among the baseline and the follow-up populations according to first year of occupational noise exposure is evaluated. Materials and Methods In 2001–2003, we conducted a baseline survey of noise- and hearing-related disorders in 11 industries with suspected high noise levels. In 2009–2010, we were able to follow up on 271 out of the 554 baseline workers (49%). Mean noise levels per industry and self-reported HPD use are described at baseline and follow-up. The association between cumulative occupational noise exposure and hearing threshold shift over the 10-year period was assessed using linear regression, and the risk of hearing loss according to year of first occupational noise exposure was evaluated with logistic regression. Results Over the 10-year period, mean noise levels declined from 83.9 dB(A) to 82.8 dB(A), and for workers exposed >85 dB(A), the use of HPD increased from 70.1 to 76.1%. We found a weak, statistically insignificant, inverse association between higher ambient cumulative noise exposure and poorer hearing (−0.10 dB hearing threshold shift per dB-year (95% confidence interval (CI): −0.36; 0.16)). The risk of hearing loss seemed to increase with earlier first year of noise exposure, but odds ratios were only statistically significant among baseline participants with first exposure before the 1980s (odds ratio: 1.90, 95% CI: 1.11; 3.22). Conclusions We observed declining industrial noise levels, increased use of HPD and no significant impact on hearing thresholds from current ambient industrial noise levels, which indicated a successful implementation of Danish hearing conservation programs.
Purpose: The purpose of this study was to evaluate the influence of occupational noise (current and cumulative doses) and psychosocial work factors (psychological demands and decision latitude) on tinnitus occurrence among workers, using objective and non-self-reported exposure measures to prevent reporting bias. Methods: In a cross-sectional study, we analyzed data from a Danish survey from 2009 to 2010 that included 534 workers from children day care units and 10 manufacturing trades. Associations between risk factors (current noise exposure, cumulative noise exposure and psychosocial working conditions) and tinnitus were analyzed with logistic regression. Results: We found no statistically significant associations between either current [OR 0.95 (95% CI 0.89; 1.01)] or cumulative [OR 0.93 (95% CI 0.81; 1.06)] occupational noise exposure and tinnitus. Likewise, results for psychosocial working conditions showed no statistically significant association between work place decision latitude [OR 1.06 (95% CI 0.94; 1.13)] or psychological demands [OR 1.07 (95% CI 0.90; 1.26)] and tinnitus. Conclusions: Our results suggest that current Danish occupational noise levels (in combination with relevant noise protection) are not associated with tinnitus. Also, results indicated that the psychosocial working conditions we observed in this cohort of mainly industrial workers were not associated with tinnitus. Therefore, psychosocial working conditions comparable to those observed in this study are probably not relevant to take into account in the evaluation of workers presenting with tinnitus.
- Nov 2016
Objective: The aim of this randomized controlled trial (RCT) was to determine whether aerobic exercise during work hours affects cardiac autonomic regulation in cleaners characterized by high levels of occupational physical activity and poor cardiorespiratory fitness. Method: Eligible cleaners (n=116) were randomized to an aerobic exercise group (n=59) or a reference group (n=57) with lectures. The intervention group received two 30-min sessions per week of supervised aerobic exercise over 4months. Diurnal measurements of heart rate variability (HRV) and physical activity (accelerometry) were obtained at baseline and at 4-month follow-up. Time and frequency domain indices of HRV were derived during work, leisure time and sleep to evaluate cardiac autonomic regulation. Linear mixed models were used to determine the effect of the intervention on HRV indices, with adjustment for age, gender and daily use of antihypertensive and/or heart medication. Results: Compared with the reference group, the exercise group increased all HRV indices apart from a reduction in LF/HF ratio from baseline to follow-up both during work (p<0.05) and leisure (p<0.05). In contrast, during sleep, the HRV indices tended to decrease in the exercise group compared with the reference group from baseline to follow-up, being significant for the HF spectral component (p=0.03). Conclusion: Among cleaners, a worksite aerobic exercise intervention improved cardiac autonomic regulation during work and leisure, but not during sleep. The health effect of this contrasting change in autonomic regulation needs further investigation.
Objectives Stress is a suspected cause of tinnitus and studies relying on self-reported stress measures have supported this hypothesis. Self-report studies may, however, have validity problems. The objective of this study was to investigate if salivary cortisol, as an objective indicator of stress activation of the HPA axis, was associated with tinnitus. Methods In a cross-sectional study, we analysed data from a Danish survey from 2010, including 632 white- and blue-collar workers from 10 manufacturing trades, children day care units and financial services. Associations between cortisol measures (awakening cortisol, awakening+30 cortisol, cortisol awakening response, evening cortisol, cortisol slope and area under the curve) and tinnitus were analysed using logistic regression. Results Overall, no statistically significant associations were observed between cortisol measures and tinnitus. Weak associations between a steeper cortisol slope across the day (reflecting higher awakening cortisol and lower evening cortisol) and tinnitus were indicated. Conclusions This observational study did not support the hypothesis that salivary cortisol, as a reflection of HPA axis activity, is associated with tinnitus. Weak indications of an association between a steeper slope of cortisol and tinnitus warrants further study.
Studies suggest that the psychological disorder arising after long-term stress differs from depression and anxiety disorders. In Sweden this stress-related condition is called exhaustion disorder (ED). ED is assigned the ICD-10 diagnostic code F43.8. The Karolinska Exhaustion Disorder Scale (KEDS) has been developed in order to assist in diagnosing patients with ED. KEDS is a short (9 items) questionnaire that addresses the core symptoms of ED: Problems with cognitive functioning, physical and mental stamina, sleeping problems, ability to recover, sensitivity to sensory impressions, reactions to demands, and feelings of irritability and anger. KEDS has been validated in Swedish ED patients and healthy individuals and showed good discriminatory power (A. Besèr et al., Scandinavian Journal of Psychology, 2014, 55, 72–82). In response to the need to identify the health condition associated with long-term stress, we decided to translate KEDS into Danish, and to test it in a group of patients in occupational health clinics in Denmark. The purpose was to investigate to which extent KEDS is able to discriminate between stress-related disorders and other disorders. In the present paper we will present the translation process, the design of the test procedure, as well as preliminary test results.
- Aug 2016
Night work is associated with a large range of acute health problems and possibly also health consequences in the long run. Yet, only very few field studies specifically investigate the effects of consecutive night shift on key physiological regulatory systems. In this field study, we investigated the effects of consecutive night shifts on three hormones, melatonin, cortisol, and testosterone, among police officers at work. More specifically, the aim was to investigate how the diurnal rhythms of melatonin, cortisol, and testosterone responded to two, four, and seven consecutive night shifts and a corresponding number of days for recovery. The study was part of the “In the Middle of the Night” project and included 73 male police officers from five different police districts. The participants were exposed to three intervention conditions: “2+2”: two consecutive night shifts followed by two consecutive day recovery days; “4+4”: four consecutive night shifts followed by four consecutive recovery days; “7+7”: seven consecutive night shifts followed by seven consecutive recovery days. On the last day with night shift and the last recovery day in each intervention, the participants collected saliva samples every 4th hour when awake. The diurnal rhythms of melatonin, cortisol, and testosterone were all affected differently by an increasing number of consecutive night shifts: the amplitude of the melatonin rhythm was suppressed by 4.9% per day (95% CI 1.4–8.2% per day; p = 0.006). The diurnal rhythm of cortisol phase was delayed with an increasing number of night shifts by 33 min/day (95% CI 18–48 min per day; p ≤ 0.001), but did not show any changes in amplitude. For the diurnal rhythm of testosterone, there was no effect of the number of consecutive night shifts and the diurnal rhythm completely followed the sleep/wake cycle. We found that there were no differences in the rhythms of melatonin, cortisol, and testosterone after 2, 4, and 7 recovery days, respectively. In conclusion, we found signs of desynchronization in terms of suppressed amplitude of melatonin and phase delay of salivary cortisol as a consequence of the increasing number of consecutive night shifts among police officers at work. Lack of synchronization has been suggested as a possible mechanism linking night work to disease, but this remains to be determined.
- Jun 2016
Objectives Occupational and residential noise exposure has been related to increased risk of cardiovascular disease. Alteration of serum lipid levels has been proposed as a possible causal pathway. The objective of this study was to investigate the relation between ambient and at-the-ear occupational noise exposure and serum levels of total cholesterol, low-density lipoprotein–cholesterol, high-density lipoprotein–cholesterol, and triglycerides when accounting for well-established predictors of lipid levels. Methods This cross-sectional study included 424 industrial workers and 84 financial workers to obtain contrast in noise exposure levels. They provided a serum sample and wore portable dosimeters that every 5-s recorded ambient noise exposure levels during a 24-h period. We extracted measurements obtained during work and calculated the full-shift mean ambient noise level. For 331 workers who kept a diary on the use of a hearing protection device (HPD), we subtracted 10 dB from every noise recording obtained during HPD use and estimated the mean full-shift noise exposure level at the ear. Results Mean ambient noise level was 79.9 dB (A) [range 55.0–98.9] and the mean estimated level at the ear 77.8 dB (A) [range 55.0–94.2]. Ambient and at-the-ear noise levels were strongly associated with increasing levels of triglycerides, cholesterol–HDL ratio, and decreasing levels of HDL–cholesterol, but only in unadjusted analyses that did not account for HPD use and other risk factors. Conclusion No associations between ambient or at-the-ear occupational noise exposure and serum lipid levels were observed. This indicates that a causal pathway between occupational and residential noise exposure and cardiovascular disease does not include alteration of lipid levels.
- Mar 2016
Among police officers in Denmark, we studied (i) how many consecutive night shifts participants preferred at baseline; (ii) preferences regarding three intervention conditions (two, four, and seven consecutive night shifts followed by the same number of days off/day shifts: '2 + 2', '4 + 4', '7 + 7') at follow-up; (iii) characteristics of participants preferring each of these intervention conditions. Questionnaire data from a crossover intervention study were used (baseline: n = 73; follow-up: n = 68). At baseline, 49% preferred four consecutive night shifts. At follow-up, 57% preferred '4 + 4', 26% preferred '2 + 2' and 26% preferred '7 + 7'. Participants, who preferred longer spells of night work experienced that night work was less demanding, found it easier to sleep at different times of the day, and were more frequently evening types compared with participants who preferred shorter spells of night work. The participants' preferences are likely to be influenced by their previous shift work experience. Practitioner Summary: We investigated police officers' preferences regarding the number of consecutive night shifts. The majority preferred four consecutive night shifts. Those who preferred the longer spells of night work found night work less demanding, found it easier to sleep at different times of the day, and were more frequently evening types.
Background: Depression and ischemic heart disease (IHD) are associated with persistent stress and autonomic nervous system (ANS) dysfunction. The former can be measured by pressure pain sensitivity (PPS) of the sternum, and the latter by the PPS and systolic blood pressure (SBP) response to a tilt table test (TTT). Beta-blocker treatment reduces the efferent beta-adrenergic ANS function, and thus, the physiological stress response. Objective: To test the effect of beta-blockers on changes in depression score in patients with IHD, as well as the influence on persistent stress and ANS dysfunction. Methods: Three months of non-pharmacological intervention aiming at reducing PPS and depression score in patients with stable IHD. Beta-blocker users (N = 102) were compared with non-users (N = 75), with respect to signs of depression measured by the Major Depressive Inventory questionnaire (MDI), resting PPS, and PPS and SBP response to TTT. Results: MDI score decreased 30% in non-users (p = 0.005) compared to 4% (p > 0.1) among users (between-group p = 0.003; effect size = 0.4). Resting PPS decreased in both the groups. Among most vulnerable patients with MDI ≥ 15, reductions in MDI score and resting PPS score correlated in non-users, only (r = 0.69, p = 0.007). Reduction in resting PPS correlated with an increase in PPS and SBP response to TTT. Conclusions: Stress intervention in patients with IHD was anti-depressive in non-users, only. Similarly, the association between the reduction in depression, reduction in persistent stress, and restoration of ANS dysfunction was only seen in non-users, suggesting a central role of beta-adrenergic receptors in the association between these factors.
Prolonged sitting is associated with increased risk for cardiovascular diseases and mortality. However, research into the physiological determinants underlying this relationship is still in its infancy. The aim of the study was to determine the extent to which occupational and leisure-time sitting are associated with nocturnal heart rate variability (HRV) in blue-collar workers. The study included 138 blue-collar workers (mean age 45.5 (SD 9.4) years). Sitting-time was measured objectively for four days using tri-axial accelerometers (Actigraph GT3X+) worn on the thigh and trunk. During the same period, a heart rate monitor (Actiheart) was used to sample R-R intervals from the electrocardiogram. Time and frequency domain indices of HRV were only derived during nighttime sleep, and used as markers of cardiac autonomic modulation. Regression analyses with multiple adjustments (age, gender, body mass index, smoking, job-seniority, physical work-load, influence at work, and moderate-to-vigorous physical activity) were used to investigate the association between sitting time and nocturnal HRV. We found that occupational sitting-time was negatively associated (p < 0.05) with time and frequency domain HRV indices. Sitting-time explained up to 6% of the variance in HRV, independent of the covariates. Leisure-time sitting was not significantly associated with any HRV indices (p > 0.05). In conclusion, objectively measured occupational sitting-time was associated with reduced nocturnal HRV in blue-collar workers. This indicates an attenuated cardiac autonomic regulation with increasing sitting-time at work regardless of moderate-to-vigorous physical activity. The implications of this association for cardiovascular disease risk warrant further investigation via long-term prospective studies and intervention studies.
- Oct 2015
Purpose: The purpose of this review is to summarize the current knowledge from field studies on how many consecutive night shifts are required for adaptation of diurnal rhythms in cortisol, melatonin and heart rate variability (HRV) to night work. Methods: A systematic search of the databases PubMed and Web of Science resulted in 18 studies selected for review. Results: Cortisol was measured in five studies, melatonin in 11 studies and HRV in four studies. Diurnal rhythms were assessed by use of several different measures based on three to eight samples per day for cortisol and melatonin and 24-h recordings for HRV. Most of the studies in the review were small studies with less than 30 participants, and most studies evaluated diurnal rhythms after only two consecutive night shifts whereas only six studies used seven or more consecutive night shifts. The majority of studies found that adaptation to night work had not occurred after two consecutive night shifts, whereas a small number found evidence for full adaptation after seven consecutive night shifts based on diurnal rhythms in cortisol and melatonin. Conclusion: There are methodological differences in the field studies analyzing diurnal rhythms and large diversity in the occupational fields studied. Nevertheless, we conclude that diurnal rhythms in cortisol, melatonin and HRV are not adapted to night work after 1-3 consecutive night shifts. Studies are needed to establish how many consecutive night shifts are needed for full adaptation of diurnal rhythms to night work.
- Aug 2015
To investigate whether acoustical refurbishment of classrooms for elementary and lower secondary grade pupils affected teachers' perceived noise exposure during teaching and noise-related health symptoms. Two schools (A and B) with a total of 102 teachers were subjected to an acoustical intervention. Accordingly, 36 classrooms (20 and 16 in school A and school B, respectively) were acoustically refurbished and 31 classrooms (16 and 15 in school A and school B, respectively) were not changed. Thirteen classrooms in school A were interim "sham" refurbished. Control measurements of RT and activity sound levels were measured before and after refurbishment. Data on perceived noise exposure, disturbance attributed to different noise sources, voice symptoms, and fatigue after work were collected over a year in a total of six consecutive questionnaires. Refurbished classrooms were associated with lower perceived noise exposure and lower ratings of disturbance attributed to noise from equipment in the class compared with unrefurbished classrooms. No associations between the classroom refurbishment and health symptoms were observed. Before acoustical refurbishment, the mean classroom reverberation time was 0.68 (school A) and 0.57 (school B) and 0.55 s in sham refurbished classrooms. After refurbishment, the RT was approximately 0.4 s in both schools. Activity sound level measurements confirmed that the intervention had reduced the equivalent sound levels during lessons with circa 2 dB(A) in both schools. The acoustical refurbishment was associated with a reduction in classroom reverberation time and activity sound levels in both schools. The acoustical refurbishment was associated with a reduction in the teachers' perceived noise exposure, and reports of disturbance from equipment in the classroom decreased. There was no significant effect of the refurbishment on the teachers' voice symptoms or fatigue after work.
- Apr 2015
We tested the hypothesis that pressure sensitivity of the sternum (PPS) is associated with autonomic nervous system (ANS) function as assessed by tilt table test (TTT). in patients with stable ischemic heart disease. (1) To evaluate an association between PPS and systolic blood pressure (SBP) and heart rate (HR) responses to TTT; and (2) to test the hypothesis that a reduction of resting PPS raises the PPS, SBP and HR responses to TTT response and lowers risk factors for ANS dysfunction (ANSD). Cross-sectional study: In 361 patients with stable ischemic heart disease we measured PPS, SBP, and HR during TTT. Intervention study: We reassessed subjects with persistent stress who concluded a stress intervention trial by a second TTT. Cross-sectional study: Resting PPS and the PPS response to TTT were correlated (r = - 0.37). The PPS response to TTT was correlated with that of SBP (r = 0.44) and HR (r = 0.49), and with the number of risk factors for ANSD (r = - 0.21) (all p < 0.0001). Intervention study: A reduction in resting PPS was associated with an increment in PPS response to TTT (r = - 0.52, p < 0.0001). The greater this increment, the greater was the reduction in ANSD risk factors (r = - 0.23; p = 0.003). The results are consistent with the hypothesis that PPS at rest and in response to TTT reflects ANS function.
This study compares the levels of algesic substances between subjects with trapezius myalgia (TM) and healthy controls (CON) and explores the multivariate correlation pattern between these substances, pain, and metabolic status together with relative blood flow changes reported in our previous paper (Eur J Appl Physiol 108:657–669, 2010). 43 female workers with (TM) and 19 females without (CON) trapezius myalgia were – using microdialysis - compared for differences in interstitial concentrations of interleukin-6 (IL-6), bradykinin (BKN), serotonin (5-HT), lactate dehydrogenas (LDH), substance P, and N-terminal propeptide of procollagen type I (PINP) in the trapezius muscle at rest and during repetitive/stressful work. These data were also used in multivariate analyses together with previously presented data (Eur J Appl Physiol 108:657–669, 2010): trapezius muscle blood flow, metabolite accumulation, oxygenation, and pain development and sensitivity. Substance P was significantly elevated in TM (p=0.0068). No significant differences were found in the classical algesic substances (p: 0.432-0.926). The multivariate analysis showed that blood flow related variables, interstitial concentrations of metabolic (pyruvate), and algesic (BKN and K+) substances were important for the discrimination of the subjects to one of the two groups (R2: 0.19-0.31, p<0.05). Pain intensity was positively associated with levels of 5-HT and K+ and negatively associated with oxygenation indicators and IL-6 in TM (R2: 0.24, p<0.05). A negative correlation existed in TM between mechanical pain sensitivity of trapezius and BKN and IL-6 (R2: 0.26-0.39, p<0.05). The present study increased understanding alterations in the myalgic muscle. When considering the system-wide aspects, increased concentrations of lactate, pyruvate and K+ and decreased oxygenation characterized TM compared to CON. There are three major possible explanations for this finding: the workers with pain had relatively low severity of myalgia, metabolic alterations preceded detectable alterations in levels of algesics, or peripheral sensitization and other muscle alterations existed in TM. Only SP of the investigated algesic substances was elevated in TM. Several of the algesics were of importance for the levels of pain intensity and mechanical pain sensitivity in TM. These results indicate peripheral contribution to maintenance of central nociceptive and pain mechanisms and may be important to consider when designing treatments.
- Oct 2014
The objective of this study was to evaluate the influence of atherogenic risk factors on hearing thresholds. In a cross-sectional study we analyzed data from a Danish survey in 2009-2010 on physical and psychological working conditions. The study included 576 white- and blue-collar workers from children's day care units, financial services and 10 manufacturing trades. Associations between atherogenic risk factors (blood lipids, glycosylated hemoglobin, smoking habits, body mass index (BMI), and ambulatory blood pressure) and hearing thresholds were analyzed using multiple linear regression models. Adjusted results suggested associations between smoking, high BMI and triglyceride level and low high-density lipoprotein level and increased low-frequency hearing thresholds (average of pure-tone hearing thresholds at 0.25, 0.5 and 1 kHz). Furthermore, an increasing load of atherogenic risk factors seemed associated with increased low-frequency hearing thresholds, but only at a borderline level of statistical significance. Associations were generally strongest with hearing levels of the worst hearing ear. We found no statistically significant associations between atherogenic risk factors and high-frequency hearing thresholds (average of pure-tone hearing thresholds at 4, 6 and 8 kHz). © 2014 S. Karger AG, Basel.
Heart rate variability (HRV) analysis, which is an important tool for activity assessment of the cardiac autonomic nervous system, very often includes the estimation of power spectra for series of interbeat intervals (IBI). Ectopic beats and artifacts have a destructive effect on the standard methods (Fourier transform, FFT) for frequency analysis. This study investigates an alternative method for calculation of the periodogram using a robust period detection (RPD). Error free IBI series of 5 minutes for 221 subjects during one day were artificially distorted by randomly changing IBI values by ±15-40%. The low to high frequency rate (LF/HF) were calculated from periodograms estimated by the FFT, RPD and Lomb (LSP) methods for both error free and distorted series and for series with removed beats. Log transformed LF/HF values for series with distorted/removed beats were compared to undistorted values by linear regression. For series with 10% of distorted IBI values the regression analysis between distorted and undistorted series showed a goodness of fit, coefficient and intercept of 0.98, 0.94 and 0.02, respectively. In comparison, the values of these parameters were (0.34, 0.46, -1.61) and (0.28, 0.42,-1.32) for the FFT and LSP methods, respectively. Similarly, the comparison between series with removed and undistorted beats yielded goodness of fit, coefficient and intercept of (0.98, 0.96, -0.01), (0.93, 0.78, -0.02) and (0.98, 0.95, 0.19) for RPD, FFT and LSP, respectively. The RPD method demonstrated superior performance compared to the FFT and LSP method by estimation of power spectral characteristics for HRV analysis.
- May 2014
Background: The overall purpose of the present study was to attain more insight in month-to-month variation of sleep duration and quality in order to improve design and interpretation of, e.g. epidemiological studies using sleep as outcome. Methods: The study design entailed monthly self-reports from 38 (26 women/12 men) daytime workers, who completed the Karolinska Sleep Diary (KSD) once a month during one year. A subgroup (n = 16) also wore actigraphs on one day every month during a year. Self-reports of bedtime, time of awakening, sleep duration, individual sleep characteristics, disturbed sleep index (DSI, 4 items) and awakening index (AWI, 3 items) were analyzed together with actigraphy-derived measures. Hours of daylight were used to test for circa-annual variation in statistical models adjusted for intake of hypnotics and alcohol, gender, age and within-person variability. Results: Hours of daylight were found to be associated to self-reported bedtime (p = 0.032) and DSI (p = 0.030), thereby indicating a circa-annual variation. Bedtime was delayed by 1.8 min (95% CI: 0.6-2.9 min) per 1 hour increase in length of daylight. Sleep was slightly more disturbed during the winter. Conclusion: Only circa-annual variation in self-reports of bedtime and DSI were observed in a healthy daytime working population, and the effects were small. Therefore potential bias due to circa-annuality in the studied parameters appears to be of limited concern in adult daytime working populations.
The study investigated the noise exposure in a group of Danish school teachers. The aims were to investigate if noise posed a risk of impairment of hearing and to study the association between classroom acoustical conditions, noise exposure, vocal symptoms, and cognitive fatigue. Background noise levels, vocal load and speaking time were measured on 35 teachers during actual classroom teaching. The classrooms were characterized acoustically by measurements of reverberation time. Before and after the workday, the teachers answered a questionnaire on fatigue symptoms and carried out two cognitive test tasks sensitive to mental fatigue. The average noise level during the lessons was 72 dB(A), but during indoor sports activities the average noise level increased 6.6 dB(A). Room reverberation time (range 0.39-0.83 s) had no significant effect on the noise level. The teachers were talking with a raised voice in 61 % of the time, and the vocal load increased 0.65 dB(A) per dB(A) increase in the average lesson noise level. An increase in voice symptoms during the workday correlated significantly with individual average noise exposure, and a decrease in performance in the two-back test correlated significantly with individual average vocal load. Noise exposure in general classrooms posed no risk of noise-induced hearing impairment in school teachers. However, the results provide evidence for an association between noise exposure and vocal load and development of vocal symptoms and cognitive fatigue after work.
Unlabelled: The validity of inclinometer measurements by ActiGraph GT3X+ (AG) accelerometer, when analysed with the Acti4 customised software, was examined by comparison of inclinometer measurements with a reference system (TrakStar) in a protocol with standardised arm movements and simulated working tasks. The sensors were placed at the upper arm (distal to the deltoid insertion) and at the spine (level of T1-T2) on eight participants. Root mean square errors (RMSEs) values of inclination between the two systems were low for the slow- and medium-speed standardised arm movements and in simulated working tasks. Fast arm movements caused the inclination estimated by the AG to deviate from the reference measurements (RMSE values up to ∼10°). Furthermore, it was found that AG positioned at the upper arm provided inclination data without bias compared to the reference system. These findings indicate that the AG provides valid estimates of arm and upper body inclination in working participants. Practitioner summary: Being inexpensive, small, water-resistant and without wires, ActiGraph GT3X+ seems to be a valid mean for direct long-term field measurements of arm and trunk inclinations when analysed by the Acti4 customised software.
The aim of this study was to investigate changes in physiological stress markers as a consequence of workplace reorganization. Moreover, we aimed to investigate changes in the psychosocial work environment (job strain, effortreward imbalance (ERI), in psychological distress (stress symptoms, perceived stress) and the mediating effect of these factors on changes in physiological stress markers. We used data from a longitudinal study that studied the health consequences of a major reorganization of non-state public offices executed in Denmark on 1 January 2007. Collection of clinical and questionnaire data was in 2006 and 2008, and in this sub-study we included 359 participants. To reflect stress reactions of the autonomic nervous system, the endocrine system and the immune system, we included 13 physiological markers. We observed significant changes in several physiological stress markers. Moreover stress symptoms and perceived stress increased significantly but did not explain the physiological changes. ERI and job strain did not change significantly and adjustment for these factors did not change the results. In this study, we found a significant association between workplace reorganization and changes in several physiological stress markers. However, these changes could not be explained by a significant change in psychological stmptoms
- Nov 2013
Background noise and room acoustics may impede social interactions by interfering with oral communication and other cognitive processes. Accordingly, recent research in school environments has showed that social relationships with peers and teachers are described more negatively in rooms with long reverberation times (RT). The purpose of this study was to investigate how RT and hearing ability (i.e., hearing thresholds [HT] and distortion product oto-acoustic emissions) were associated with schoolteachers' perceptions of the social climate at work and their intentions to stay on the job. Schoolteachers (n = 107) from 10 schools that worked in classrooms classified by acoustical experts as "short RT" (3 schools, mean RT 0.41-0.47 s), "medium RT" (3 schools, mean RT 0.50-0.53 s), and "long RT" (4 schools, mean RT 0.59-0.73 s) were examined. Teachers who worked in classrooms with long RT perceived their social climate to be more competitive, conflict laden, and less relaxed and comfortable. They were more doubtful about staying on the job. Even if the teachers were generally satisfied with their work the results suggest that the comfort at work may have been further improved by acoustical interventions that focus on reducing sound reflections in the classrooms. Yet, due the study design and the novelty of the findings the potential practical significance of our observations remains to be evaluated.
- Apr 2013
Background: Chronic stress is prevalent in patients with ischemic heart disease (IHD) and worsens the long-term prognosis. Chronic stress is vaguely defined, but is associated with depressive symptoms, reduced psychological wellbeing, and reduced quality of life (QOL). Stress seems to induce hyperalgesia.The aim of the present study was to evaluate hyperalgesia by pressure pain sensitivity (PPS) in patients with IHD, and compare PPS to questionnaires measuring depressive symptoms, reduced psychological wellbeing, and QOL as markers of stress. Design. A cross-sectional study of 361 subjects with IHD. Methods: PPS was measured on the sternum, and compared to the questionnaires: Clinical stress symptoms score (CSS), Major Depression Inventory (MDI), WHO-5 Wellbeing Index, and SF-36 QOL score. Results: PPS correlated to CSS (r = 0.20, p < 0.001), MDI (r = 0.14, p = 0.02), SF-36 mental component summary score (MCS) (r = - 0.10, p = 0.049), SF-36 physical component summary score (PCS) (r = - 0.17, p = 0.001), and self-perceived stress level (r = 0.15, p = 0.006). CSS correlated similarly (r = 0.5-0.7, all p < 0.001). Comparing subjects within the lowest vs. highest tertiles of PPS and CSS, the mean MDI score was 4 vs. 15, WHO-5 was 77 vs. 53, SF-36 PCS was 53 vs. 43, and SF-36 MCS was 58 vs. 46; all p < 0.001. Conclusions: PPS reflected to a modest degree markers of chronic stress in IHD. PPS and CSS together might be useful as easy-to use tools for evaluating these markers in IHD patients.
- Feb 2013
Beyond noise annoyance and voice problems, little is known about the effects that noise and poor classroom acoustics have on teachers' health and well-being. The aim of this field study was therefore to investigate the effects of perceived noise exposure and classroom reverberation on measures of well-being. Data on self-reported noise exposure, job satisfaction, fatigue after work, and interest in leaving the job were obtained from 283 teachers at 10 schools in Copenhagen, Denmark. In addition, the schools' acoustical working environment was classified as "low reverberation time (RT)" (3 schools, RT = 0.41-0.47 s), "medium RT" (3 schools, RT = 0.50-0.53 s), or "high RT" (4 schools, RT = 0.59-0.73 s). Significant associations were found between high RT and noise exposure, and, respectively, low job satisfaction, lack of energy after work, and interest in leaving the job. Noise exposure was also associated with lack of motivation and sleepiness. The results demonstrate the importance of good classroom acoustic conditions for teachers' well-being.
Aims: To describe the distribution of subjective health complaints (SHCs) in a Danish working population and the associations between SHC and register based sickness absence. Methods: The study entailed 2876 men and 3574 women aged 18-59 years that constituted the 2005 panel in the Danish Work Environment Cohort Study (DWECS). All had completed a subjective health complaints inventory and the Nordic Musculoskeletal Questionnaire (NMQ). Seven SHC/NMQ indices were constructed and merged with subsequently collected data on prolonged sickness absence periods (each period > 14 days) that was registered in the national Danish register on social transfer payments: the DREAM register. Ordinal logistic regression was used to model the cumulative odds for sickness absence as a function of strata. Results: The majority of participants reported at least one SHC during a 30-day period (circa 89% of the men and 95% of the women). The reports of severe SHC, defined as recurring SHC within the 30-day period, were less common. About 55% of the men and 68% of the women reported at least one severe SHC during a 30-day period. The odds ratios of sickness absence increased with the number of SHC a participant acknowledged. The odds ratios were slightly reduced after adjusting for age, disease history and social class. Conclusions: The majority of the working population in Denmark report at least one SHC during a 30-day period. Roughly half of the population report having at least one recurrent (often to very often) SHC during the last 30-days (severe SHC). Reporting the presence of several SHCs increases the likelihood of having more prospectively registered periods of sickness absence above two weeks.
Background: The aim of this study was to validate a triaxial accelerometer setup for identifying everyday physical activity types (ie, sitting, standing, walking, walking stairs, running, and cycling). Methods: Seventeen subjects equipped with triaxial accelerometers (ActiGraph GT3X+) at the thigh and hip carried out a standardized test procedure including walking, running, cycling, walking stairs, sitting, and standing still. A method was developed (Acti4) to discriminate between these physical activity types based on threshold values of standard deviation of acceleration and the derived inclination. Moreover, the ability of the accelerometer placed at the thigh to detect sitting posture was separately validated during free living by comparison with recordings of pressure sensors in the hip pockets. Results: Sensitivity for discriminating between the physical activity types sitting, standing, walking, running, and cycling in the standardized trials were 99%-100% and 95% for walking stairs. Specificity was higher than 99% for all activities. During free living (140 hours of measurements), sensitivity and specificity for detection of sitting posture were 98% and 93%, respectively. Conclusion: The developed method for detecting physical activity types showed a high sensitivity and specificity for sitting, standing, walking, running, walking stairs, and cycling in a standardized setting and for sitting posture during free living.
Psychosocial risk factors are often conceptualised as explanatory constructs that reflect environmental exposures. To date, the predominant method to operationally define such environmental exposures has been via self-report questionnaires (eg, the Job Content Questionnaire (JCQ) and the Copenhagen Psychosocial Questionnaire (COPSOQ)1 ,2). However, methodological concerns have been raised. One such concern is the extent to which responses can be generalised to actual …
Purpose: To investigate the association between self-reported exposure to disturbing noise and risk of long-term sickness absence (LTSA) for more than two consecutive weeks among office workers. Methods: LTSA was measured using register data that were linked to survey data from 2,883 office workers aged 18-59 who were surveyed in 2005 on exposure to disturbing noise. The risk of LTSA was investigated using Cox proportional hazards model. Results: Of the study population, 4.4 % had LTSA in the 1-year follow-up period. Compared to office workers who were 'rarely or never' exposed to disturbing noise at work, office workers who reported being 'frequently' exposed to disturbing noise had a significantly increased estimated risk of LTSA when adjusting for age, gender, smoking status, and managerial position (HR = 1.90; 95 % CI, 1.12-3.22). After additional adjustment for psychosocial work conditions, the estimated risk of LTSA for office workers who were frequently exposed to disturbing noise became marginally insignificant (HR = 1.73; 95 % CI, 0.99-3.01). A subgroup analysis showed that women who reported being frequently exposed to disturbing noise had a significantly increased estimated risk of LTSA (HR = 1.94; 95 % CI, 1.04-3.64), whereas the corresponding risk for men was insignificant (HR = 1.28; 95 % CI, 0.37-4.41). Conclusions: This study indicates that frequent self-reported exposure to disturbing noise at work is associated with increased risk of LTSA among office workers and that this association may be stronger for women than for men.
Background Prevalence of cardiovascular risk factors is unevenly distributed among occupational groups. The working environment, as well as lifestyle and socioeconomic status contribute to the disparity and variation in prevalence of these risk factors. High physical work demands have been shown to increase the risk for cardiovascular disease and mortality, contrary to leisure time physical activity. High physical work demands in combination with a low cardiorespiratory fitness infer a high relative workload and an excessive risk for cardiovascular mortality. Therefore, the aim of this study is to examine whether a worksite aerobic exercise intervention will reduce the relative workload and cardiovascular risk factors by an increased cardiorespiratory fitness. Methods/design A cluster-randomized controlled trial is performed to evaluate the effect of the worksite aerobic exercise intervention on cardiorespiratory fitness and cardiovascular risk factors among cleaners. Cleaners are eligible if they are employed ≥ 20 hours/week, at one of the enrolled companies. In the randomization, strata are formed according to the manager the participant reports to. The clusters will be balanced on the following criteria: Geographical work location, gender, age and seniority. Cleaners are randomized to either I) a reference group, receiving lectures concerning healthy living, or II) an intervention group, performing worksite aerobic exercise “60 min per week”. Data collection will be conducted at baseline, four months and 12 months after baseline, at the worksite during working hours. The data collection will consist of a questionnaire-based interview, physiological testing of health and capacity-related measures, and objective diurnal measures of heart rate, physical activity and blood pressure. Primary outcome is cardiorespiratory fitness. Discussion Information is lacking about whether an improved cardiorespiratory fitness will affect the cardiovascular health, and additionally decrease the objectively measured relative workload, in a population with high physical work demands. Previous intervention studies have lacked robust objective measurements of the relative workload and physical work demands. This study will monitor the relative workload and general physical activity before, during after the intervention, and contribute to the understanding of the previously observed opposing effects on cardiovascular health and mortality from occupational and leisure time physical activity. Trial registration The study is registered as ISRCTN86682076.
- Jan 2012
This study investigated effects on comfort, symptoms, and office work performance of exposure to office noise. Forty-nine subjects who were employees working in open-plan offices participated in two full-day experiments simulating an ordinary work day; one day with and one day without exposure to pre-recorded office noise. Exposure to office noise affected negatively ratings of adverse perceptions, selected symptoms, and self-assessed performance, but not the performance of the simulated office tasks. Occupants who in their daily work were disturbed by open-plan office noise were less tolerant to the noise exposure than those who were not.
- Dec 2011
A high proportion of school teachers report that they are disturbed by noise during teaching. The aim of the study was therefore to identify determinants of self-reported noise exposure and disturbance attributed to noise among secondary school teachers (n = 419) in 10 schools in Copenhagen, Denmark. The schools were selected to show contrasts in classroom reverberation times (RT), and were classified as “Short RT” (3 schools, mean RT 0.41–0.45 s), “Medium RT” (3 schools, mean RT 0.51–0.55 s) and “Long RT” (4 schools, mean RT 0.62–0.73 s). Significant determinants of self-reported noise exposure were a high number of children in the class, young age of the children, and low teacher seniority. “Long RT” classification was of borderline significance. Significant determinants of disturbance attributed to noise from children in the class were teacher seniority and “Long RT” acoustic classification of the school. The associations between work characteristics and noise disturbance measures were attenuated by low self-rated work capacity, suggesting that the consequences of noise and poor acoustics may not be limited to disturbance attributed to noise, but may have a wide negative impact on the perceived working environment.
To examine the association between autonomic regulation and length of pain-related sick leave in subjects receiving a cognitive behavioural therapy-based return to work intervention. Sixty-five persons (29 men, 36 women) on pain-related sick leave participated in the study. Electrocardiograms were recorded in the clinic during supine rest, passive head-up tilt, standing, and seated rest, and in the home during seated rest and sleep. Spectral components of heart rate variability were derived from short-term (5 min) segments of electrocardiogram recordings. The number of days on sick leave was obtained from register data for 3 months before to 6 months after seeking care at the primary healthcare clinic. Extended sick leave (> 121 days) compared with short sick leave (< 29 days) was associated with higher heart rate, and lower heart rate variability in supine rest and the seated position. The associations in supine rest were marginally weakened by adjusting for offensive behaviours at work. (for example, exposure to bullying, sexual harassment, unpleasant teasing, etc.) Higher heart rate and lower heart rate variability measured in the awake resting condition predicts extended sick leave in care-seeking individuals. Further research is needed to clarify the underlying nature and causal role of altered autonomic regulation with regard to extended pain-related sick leave.
- Jul 2011
- 10th International Congress on Noise as a Public Health Problem, the International Commission on Biological Effects of Noise (ICBEN) 2011.
We have previously observed that poor classroom acoustics (long reverberation time) and other work related conditions contribute to the perceived noise exposure of schoolteachers and the disturbance attributed to noise in the classroom. The present study aimed to investigate to what extent the self-reported noise exposure and disturbance attributed to noise in the classroom were associated with high noise levels and hearing deficiency. Therefore, self-reported noise exposure, disturbance attributed to noise in class and hearing loss was compared to determinations of pure-tone audiometry (PTA) and distortion product oto-acoustic emissions (DPOAE). There was a statistically significant association between self-reported noise exposure and the degree of disturbance attributed to noise in the classroom, respectively, and measurements of DPOAE at high frequencies, and contrary to expectations higher scores in the disturbance of teaching by noise was associated with better hearing.
- Jul 2011
- 10th International Congress on Noise as a Public Health Problem, the International Commission on Biological Effects of Noise (ICBEN)
Background: Noise is a source of disturbance and annoyance among school teachers, even though the sound levels are well below the level associated with increased risk of hearing impairment. However, little is known about other effects associated with noise exposure in this group and to what extent the acoustic environment contributes. Objective: The study aimed at identifying the impact of classroom acoustics and self-reported noise on fatigue after work, job satisfaction, and intentions to quit the job among 283 school teachers in 10 public schools in Copenhagen, Denmark. Methods: Questionnaire survey combined with independent expert assessments of the schools acoustical quality and complemented with measurements of classroom reverberation times. Results: Self-reported noise exposure was significantly associated with low job satisfaction and with increased fatigue after work, particularly the fatigue dimension lack of energy. Working in schools with classrooms characterized by relatively long reverberation time (0.62-0.73 s) compared to schools with classrooms of short reverberation time (0.41-0.45 s) was associated with low job satisfaction, lack of energy, and an increased risk of considering quitting the job. Conclusions: Both self-reported noise exposure and classroom acoustics were independently associated with negative evaluations of the working environment.
- Jun 2011
The current study analyzed the relationship between psychosocial work environment assessed by the Effort Reward Imbalance Model (ERI-model) and heart rate variability (HRV) measured at baseline and again, two years later, as this relationship is scarcely covered by the literature. Measurements of HRV during seated rest were obtained from 231 public sector employees. The associations between the ERI-model, and HRV were examined using a series of mixed effects models. The dependent variables were the logarithmically transformed levels of HRV-measures. Gender and year of measurement were included as factors, whereas age, and time of measurement were included as covariates. Subject was included as a random effect. Effort and effort reward imbalance were positively associated with heart rate and the ratio between low frequency (LF) and high frequency power (HF) and negatively associated with total power (TP) and HF. Reward was positively associated with TP. Adverse psychosocial work environment according to the ERI-model was associated with HRV, especially in the form of vagal withdrawal and most pronounced in women.
The theory behind the Job Content Questionnaire (JCQ) presumes that the "objective" social environment is measurable via self-report inventories such as the JCQ. Hence, it is expected that workers in identical work will respond highly similar. However, since no studies have evaluated this basic assumption, we decided to investigate whether workers performing highly similar work also responded similarly to the JCQ. JCQ data from a rubber-manufacturing (RM: n = 95) and a mechanical assembly company (MA: n = 119) were examined. On each worksite, men and women performed identical machine-paced job tasks. A population sample (n = 8,542) served as a reference group. In both the RM and MA groups, the job support questions were rated most similar. Yet, there was a substantial variation as regards choosing to agree or disagree with single JCQ items. The variation was also reflected in the scale scores. In the RM and MA groups, the variance of job demand and job control scores was 64-87% of that of the population sample. For job support scores, the corresponding variation was 42-87%. Conducting highly similar work does not lead to highly similar reports in the JCQ. In view of the large response variation, it seems that the attempt to avoid personal influence by minimizing the self-reflexive component in the questions asked, and using response alternative that indicates degree of agreement, does not seem to work as intended.
A number of small portable systems that can measure HRV are available to address questions related to autonomic regulation in free-living subjects. However, ambulatory HRV measurements obtained through use of these systems have not previously been validated against standard clinical measurements such as Holter recordings. The objective of this study was to validate HRV obtained using a commonly used system, Actiheart, during occupational and leisure-time activities. Full-day ambulatory electrocardiography (ECG) signals were recorded from 8 females simultaneously using Actiheart and Holter recorders, and signals were processed to RR-interval time series. Segments of 5-minute duration were sampled every 30 minutes, and spectral components of the heart rate variability were calculated. Actiheart and Holter values were compared using Deming regression analysis and Bland-Altman plots. In total, 489 segments were available with an HRV value from both Actiheart and Holter recordings after filtering out segments with >10% interpolated beats. No systematic differences between Actiheart and Holter HRV were found. The random deviations between Actiheart and Holter were comparable to the repeatability standard deviation between consecutive Holter measurements. The results show that Actiheart is suited as a stand-alone ambulatory method for heart rate variability monitoring during occupational and leisure-time activities.
To examine the risk of sleep problems associated with work stress (job strain, job demands, and decision authority), worries and pain and to investigate the synergistic interaction between these factors and traffic noise. Sleep problems and predictor variables were assessed in a cross-sectional public health survey with 12,093 respondents. Traffic noise levels were assessed using modelled A-weighted energy equivalent traffic sound levels at the residence. The risk of sleep problems was modelled using multiple logistic regression analysis. With regard to sleep problems not attributed to any external source (general sleep problems), independent main effects were found for traffic noise (women), decision authority (women), job strain, job demands, suffering from pain or other afflictions, worries about losing the job, experiencing bullying at work, having troubles paying the bills, and having a sick, disabled, or old relative to take care of (women). Significant synergistic effects were found for traffic noise and experiencing bullying at work in women. With regard to sleep problems attributed to traffic noise, strong synergistic interactions were found between traffic noise and, respectively, job demands (men), having pain or other afflictions, taking care of a sick, old, or disabled relative, and having troubles paying the bills. Main effects were found for worries about losing the job, experiencing bullying at work, job strain (men), and decision authority (men). Synergistic interactions could potentially contribute with 10-20% of the sleep problems attributed to traffic noise in the population. Work stress, pain, and different worries were independently associated with general sleep problems and showed in general no synergistic interaction with traffic noise. In contrast, synergistic effects between traffic noise and psychological factors were found with regard to sleep problems attributed to traffic noise. The synergy may contribute significantly to sleep problems attributed to traffic noise in the population.
- Dec 2010
Noise in non-industrial workplaces is an increasing problem. Annoyance and complaints over noise are frequently reported in these workplaces, whereas the risk of hearing damage is usually not the major concern. An important question arises for this type of noise of low to moderate intensity; that is, if it could be a cause of increased sickness absence, for example, via a mechanism starting with job dissatisfaction or via health problems caused by the noise exposure. This paper discusses this question starting from epidemiological studies on sickness absence, and supplemented with field and laboratory studies that address intermediate steps on the path to sickness absence, such as job dissatisfaction, symptoms, and physiological stress reactions.Only 3 epidemiological studies have investigated the effect of occupational noise on sickness absence. In the one study most pertinent to the question raised above, noise was associated with increased sickness absence in women holding jobs with complex work tasks.No firm conclusions can be made based on the studies that have illuminated possible intermediate steps to sickness absence. One reason is the wide variety of scopes and contexts addressed in these studies; the workplace exposures that have been investigated spans noise in schools, open-plan offices, hospitals and noise from ventilation systems, etc. Another reason is the presence of major weaknesses in many of the studies, such as confounding effects and problematic exposure assessments. It is concluded that based on the level of the current evidence an association between occupational noise exposure of low to moderate level and sickness absence is possible, but to settle the question more high quality studies are needed.
- Oct 2010
The current study analyzed the relationship between psychosocial factors measured at baseline and heart rate variability (HRV) and salivary cortisol measured at baseline and again, six years later. In 2002 and 2008, measurements of HRV and salivary cortisol at three time points were obtained from 70 healthy participants (48 women and 22 men). The associations between the psychosocial factors measured in 2002 and the dependent variables, HRV and salivary cortisol measured in 2002 and 2008, were examined using a series of repeated measures ANCOVAs. The dependent variables were as follows: the logarithmically transformed levels of total power (LnTP), high frequency power (LnHF), the ratio between low and high frequency power (LnLF/HF) and salivary cortisol (LnCortisol). For women, high social status was associated with high LnTP, high LnHF, and low LnLF/HF. In work, lack of control was associated with low LnTP, and lack of support was associated with an increased LnLF/HF ratio. For men, high social status was associated with low LnTP, low LnHF and high LnCortisol. Greater number of hours spent doing housework was associated with both low LnLF/HF and low LnCortisol, whereas a large imbalance between effort and reward was associated with low LnTP and high LnCortisol. Despite the small sample size, this study demonstrated that psychosocial factors impact levels of activity in the allostatic systems.
- Jun 2010
- INTER-NOISE 2010, the 39th International Congress and Exposition on Noise Control Engineering
Objective: The study aimed at identifying risk factors of being disturbed by noise at work among teachers in public schools in Copenhagen, Denmark. Methods: Four hundred and nineteen teachers on 10 public schools in Copenhagen were invited to participate in the study. The schools were selected to represent contrasts with respect to classroom reverberation times. In total, 283 teachers (67.5%) responded to the questionnaire on noise exposure and annoyance. Results: The risk of reporting a high level of noise exposure (at least 1/2 of the working time) was increased if (a) the children in the class were young, (2) the class was large, or (3) the teacher had little teaching experience. The risk of perceiving noise from the class as highly disturbing was increased if (1) the classroom was of medium or long reverberation time (compared to short reverberation time), or (2) if the children in the class were young. High age of the teacher was protective with regard to noise annoyance. Conclusions: Both acoustical and psychosocial factors contribute to noise annoyance. The results can help to identify effective measures against noise-related disturbance of teaching activities in schools.
- Jun 2010
- INTER-NOISE 2010, the 39th International Congress and Exposition on Noise Control Engineering
This study examined the relationship between objective measures of hearing thresholds (HT) and distortion product oto-acoustic emissions (DPOAE) and self-reported hearing ability, tinnitus and hyperacusis. The participants were 50 opera-orchestral musicians that were at elevated risk of noise induced hearing loss (NIHL). Self rating of hearing ability on a scale seems to be preferential to categorical question regarding hearing loss (yes/no) in questionnaires for professional orchestral musicians, and is primarily associated with changes in both HT and DPOAE in the 3-6 kHz frequency range like NIHL in industrial workers. Reports of daily tinnitus daily were associated in with increase in HT at 6 kHz, but sporadic tinnitus (weekly or monthly) were not associated with any consistent changes in HT or DPOAE. The fraction of musicians reporting hyperacusis (yes/no) did not have worse hearing in the assessments than the rest of the musicians.
- Jun 2010
- INTER- NOISE 2010, the 39th International Congress and Exposition on Noise Control Engineering,
The present study examined hearing impairment by measurements of hearing thresholds and distortion product oto-acoustic emissions (DPOAE) in a group of musicians that had an elevated risk of noise induced hearing loss. The measurements of DPOAE showed a clear reduction in musicians that otherwise only showed slight reductions in hearing thresholds in the mid- to high frequency range. Hence, measurements of DPOAE seem to yield a better estimate of initial signs of hearing impairment than the traditional assessment of hearing thresholds. Further, by optimization of this technique, reliable measurements of DPOAE in the whole mid- to high-frequency range of hearing can be performed twice within 3-4 minutes.
The aim of this investigation was to study female workers active in the labour market for differences between those with trapezius myalgia (MYA) and without (CON) during repetitive pegboard (PEG) and stress (STR) tasks regarding (1) relative muscle load, (2) trapezius muscle blood flow, (3) metabolite accumulation, (4) oxygenation, and (5) pain development. Among 812 female employees (age 30-60 years) at 7 companies with high prevalence of neck/shoulder complaints, clinical examination identified 43 MYA and 19 CON. At rest, during PEG, and STR the trapezius muscle was measured using (1) EMG and MMG, (2) microdialysis, and (3) NIRS. Further, subjective pain ratings were scored (VAS). EMGrms in %MVE (Maximal Voluntary EMG-activity), was significantly higher among MYA than CON during PEG (11.74 +/- 9.09 vs. 7.42 +/- 5.56%MVE) and STR (5.47 +/- 5.00 vs. 3.28 +/- 1.94%MVE). MANOVA showed a group and time effect regarding data from the microdialysis: for MYA versus CON group differences demonstrated lower muscle blood flow and higher lactate and pyruvate concentrations. Potassium and glucose only showed time effects. NIRS showed similar initial decreases in oxygenation with PEG in both groups, but only in CON a significant increase back to baseline during PEG. VAS score at rest was highest among MYA and increased during PEG, but not for CON. The results showed significant differences between CON and MYA regarding muscle metabolism at rest and with PEG and STR. Higher relative muscle load during PEG and STR, insufficient muscle blood flow and oxygenation may account for the higher lactate, pyruvate and pain responses among MYA versus CON.
Recently, it has become clear that the complexity of environmental health issues requires an approach that takes into account the complexities, interdependencies and uncertainties of the real world. An urgent issue that has surfaced is the need for accurate tools to better describe exposure characterization to environmental chemicals. By including human biomonitoring (HBM) data, a greater precision in exposure and associated risk estimates and more accurate dose-response relationships may be achieved. A restricting issue still is the availability of reliable and comparable HBM data. The aim of the current study was twofold: (1) to find out whether it is practically feasible to collect raw, individual HBM data across Europe; and (2) to evaluate the comparability and use of these HBM data for environmental health impact assessment at a European scale. Blood-lead (B-Pb) was selected as the chemical of choice because of its long history as an environmental pollutant in HBM programs and its known public health relevance. Through literature search and identification of HBM experts across Europe, HBM programs that measured B-Pb were identified and asked to share individual data on age, gender and B-Pb levels. Following this request, more than 20,000 individual data points from 8 European countries were collected. Analysing these data made clear that it is difficult to use disparate data collections because of the inherent variability with respect to the gender and age of participants and calendar-years sampled. When these confounders were taken however, there was no additional variability in B-Pb distributions among different countries. It was concluded that while it is possible to collect HBM data from different sources across Europe, the need to get data from comparable (sub-)populations is essential for appropriate use and interpretation of HBM data for environmental health impact assessment.
- Oct 2009
Although ambulatory measurements of heart rate variability (HRV) are widely used, the reproducibility and seasonal variation of ambulatory sampled short-term HRV measurements in healthy participants has not been investigated before. In the present study we collected ambulatory ECGs from 19 healthy participants monthly for 12 months, and for a sub-group of 12 participants weekly for one month. Frequency-domain HRV-metrics were calculated for 5 min ECG segments during (i) a 15-min self-selected rest period (awake period), and (ii) a 30-min sleep period starting 45 min after estimated sleep onset. Total, within- and between-subject coefficient of variation (CV) and seasonal variation were estimated for ln (TP), ln (LFP), ln (HFP), ln (LF/HF), LFnu, HFnu, the mean heart period and the ECG derived respiratory frequency.The within- and between-subject CV varied considerably between different variables, from 10% for ln (TP) and ln (LFP) to 100% for ln (LF/HF). Within- and between-subject CV of ln (HFP), LFnu and HFnu were 10-40%. A weak, but significant, seasonal variation was found for ln (TP) (p = 0.05), ln (LFP) (p0.05) and the respiratory frequency (p0.01), but the seasonal variation did not affect the within-subject CV. Furthermore, sample size calculations demonstrated that the reproducibility was sufficient for ambulatory HRV measurements to be used to study autonomic cardiac regulation in healthy populations.
- May 2009
Although ambulatory measurements of heart rate variability (HRV) are widely used, the reproducibility and seasonal variation of ambulatory sampled short-term HRV measurements in healthy participants has not been investigated before. In the present study we collected ambulatory ECGs from 19 healthy participants monthly for 12 months, and for a sub-group of 12 participants weekly for one month. Frequency-domain HRV-metrics were calculated for 5 min ECG segments during (i) a 15-min self-selected rest period (awake period), and (ii) a 30-min sleep period starting 45 min after estimated sleep onset. Total, within- and between-subject coefficient of variation (CV) and seasonal variation were estimated for ln (TP), ln (LFP), ln (HFP), ln (LF/HF), LFnu, HFnu, the mean heart period and the ECG derived respiratory frequency.The within- and between-subject CV varied considerably between different variables, from < 10% for ln (TP) and ln (LFP) to >100% for ln (LF/HF). Within- and between-subject CV of ln (HFP), LFnu and HFnu were 10-40%. A weak, but significant, seasonal variation was found for ln (TP) (p = 0.05), ln (LFP) (p<0.05) and the respiratory frequency (p<0.01), but the seasonal variation did not affect the within-subject CV. Furthermore, sample size calculations demonstrated that the reproducibility was sufficient for ambulatory HRV measurements to be used to study autonomic cardiac regulation in healthy populations.
Objectives To investigate the effects of cognitively demanding work tasks and office noise on heart rate variability (HRV), cardiovascular responses and electromyography (EMG) activity in the trapezius muscles. Methods Ten female volunteers were exposed to simulated open-plan office noise for 35 min (Leq 65 dBA), while engaged in cognitively demanding tasks. Task performance, self-rated stress and energy, affective state, perceived exertion in the shoulders and in the head, EMG in the left and right trapezius muscle, blood pressure, heart period length, HRV, and salivary cortisol were measured. Results Cognitively demanding work tasks were associated with changes in HRV, systolic blood pressure and EMG that reflects increased sympathetic activity in the autonomic nervous system. No effect of noise was observed, except for a higher rating of perceived exertion in the head and, contrary to expectations, a 4% lower diastolic blood pressure in the noise conditions. Conclusions Psychophysiological measures reflected the mental load imposed by cognitive work tasks. Short-term exposure to office noise resulted in increased ratings of perceived exertion in the head, but not in physiological stress reactions.
Self-reported noise exposure is on the rise in Denmark. Little is known, however, about the social consequences, including sickness absence, of noise exposure. The aim of this paper was to investigate the association between self-reported noise exposure and long-term sickness absence. The association was investigated using the Cox proportional hazards model to analyze outcomes in Danish register data on the basis of Danish survey data (5357 employees aged 18-69 in 2000). The analyses showed that self-reported noise exposure was significantly associated with long-term sickness absence for both men and women when adjusting for demographic factors and health behavior. After further adjustment for physical workload at work the association between noise exposure and sickness absence disappeared for women, but not for men. Men that reported to be exposed to loud noise between one-quarter and three-quarters of their time at work had an increased risk of 43% (CI: 10-85%) for sickness absence of two weeks or longer compared to men that reported never to be exposed to loud noise. Men that reported to be little/rarely exposed to loud noise had an increased risk of 37% (CI: 7-76%). Men that reported to be exposed to loud noise more than three-quarters of their time at work did not have an increased risk of sickness absence. This latter result might be due a healthy worker effect and/or more frequent use of hearing protection in this group. Along with evidence from previous studies these results provide further support for an association between occupational noise exposure and sickness absence.
- Dec 2008
The trapezius muscle often develops pain as the result of repetitive and stressful work tasks although it is unclear to what extent this pain is due to alterations in muscle concentrations of algesic/nociceptive substances. Twenty women with chronic neck- and shoulder pain (TM) whose work required highly repetitive work tasks and 20 pain-free female colleagues (CON) were studied during and after a full 8-hour workday. We collected microdialysates from their dominant/most painful trapezius muscle; concentrations of serotonin, glutamate, lactate, pyruvate, potassium, bradykinin, and cytokines and blood flow were determined. In addition, we measured surface electromyogram, task exposure level, pain intensity, perceived mental stress, and urine-cortisol. In connection to the clinical neck and shoulder examination, we determined pressure pain thresholds (PPTs) over the trapezius and tibialis muscles. TM had higher concentrations of glutamate (71+/-42 vs. 36+/-15 micromol l(-1)) and pyruvate (187+/-89 vs. 125+/-63 micromol l(-1)) than CON. Interstitial serotonin was higher in TM (before work: 10.6+/-10.8 vs. 2.2+/-1.2 nM; after work: 9.2+/-8.3 vs. 1.5+/-2.9 nM). The trapezius blood flow during the working day was higher in TM than in CON. TM had lower PPT and higher pain intensity throughout the working day. No differences in EMG, task exposure level, mental stress, or urine-cortisol in the groups were found. These findings support the idea that peripheral nociceptive processes are activated in occupationally active subjects, who are diagnosed with trapezius myalgia. In contrast, no sign of low blood flow or increased stress or muscle activity markers were found in TM.
- Oct 2008
The origins of chronic muscle pain development and maintenance are debated regarding the relative contributions of peripheral nociception and central pain processing. Bradykinin (BKN) and kallidin (KAL) have been suggested to be algesic kinins involved in muscle pain. This in vivo study investigates whether there were significant differences in interstitial muscle concentrations of BKN and KAL between chronic work-related trapezius myalgia (TM), chronic whiplash associated disorders (WAD), and healthy controls (CON). These subjects were studied at rest, during a 20-min repetitive low-force exercise and recovery. The interstitial concentrations of BKN and KAL of trapezius were determined using the microdialysis technique. The interstitial concentration of KAL was overall significantly higher in TM than in CON. [KAL] and [BKN] increased significantly during the brief exercise in all groups. The increase in [BKN] during exercise was significantly higher in TM than in the other two groups, whereas the increase in [KAL] during exercise was highest in WAD. In chronic pain, positive correlations existed between the two kinins and the difference in pain intensity between recovery and baseline. In this in vivo study of two groups of patients with chronic pain clinically involving the trapezius muscle, we found alterations - most prominent in TM - in the interstitial concentrations of BKN and KAL. The results indicated that the two kinins were involved in aspects of hyperalgesia.
- Feb 2008
The mechanisms behind the development of chronic trapezius myalgia in patients with whiplash associated disorders (WAD) appear to involve both peripheral and central components, but the specific contribution of alterations in muscle is not clear. Female patients with WAD and involvement of trapezius (N=22) and female controls (N=20; CON) were studied during an experiment compromised of rest (baseline), 20min repetitive low-force exercise and 120min recovery. Their interstitial concentrations of serotonin (5-HT), glutamate, lactate, pyruvate, potassium, interleukin-6 (IL-6), and blood flow were determined in the trapezius muscle using a microdialysis technique. Pressure pain thresholds (PPT) over trapezius and tibialis anterior muscles were also assessed. In WAD, we found signs of generalized hypersensitivity according to PPT. The WAD group had significantly higher interstitial [IL-6] and [5-HT] in the trapezius than the CON. [Pyruvate] was overall significantly lower in WAD, and with lactate it showed another time-pattern throughout the test. In the multivariate regression analysis of pain intensity [5-HT] was the strongest regressor and positively correlated with pain intensity in WAD. In addition, blood flow, [pyruvate], and [potassium] influenced the pain intensity in a complex time dependent way. These findings may indicate that peripheral nociceptive processes are activated in WAD with generalized hypersensitivity for pressure and they are not identical with those reported in chronic work-related trapezius myalgia, which could indicate different pain mechanisms.
- Nov 2007
Airborne particulate matter (PM) was sampled by use of an electrostatic sampler in an oven hall and a receiving hall in a waste-incineration energy plant, and from urban air in a heavy-traffic street and from background air in Copenhagen. PM was sampled for 1–2 weeks, four samples at each site. The samples were extracted and examined for mutagenicity in Salmonella typhimurium strains TA98, YG1041 and YG5161, for content of inorganic elements and for the presence of eight polycyclic aromatic hydrocarbons. The induction of IL-6 and IL-8 mRNA expression and the presence of DNA damage – tested by the comet assay – were determined after 24-h incubations with human A549 lung epithelial cells.
- Feb 2007
The European Council Directive 98/24 on the protection of the health and safety of workers exposed to chemical agents sets out provisions for environmental and biological monitoring, making specific reference to binding limit values and health surveillance measures for those with exposure to lead To compare how the Directive has been implemented at a national level in EU countries and to determine whether workers receive equivalent protection. Information on selected key issues was collected from 14 EU countries by means of a structured questionnaire. National occupational exposure limit values generally reflect that set by the Directive (0.15 mg/m(3)), but in five cases lower limits are set. National binding biological limit values range from 20 microg/100 ml blood in one country up to 80 microg/100 ml blood in others. The risk to the unborn child is generally recognised with specific measures for women of child-bearing potential or those that are pregnant or breast feeding. In only three countries are special arrangements included for young workers. Limits at which medical surveillance is put into effect are more consistent at 40 microg/100 ml in most countries. The Directive also refers to guidelines for health surveillance but none have been issued with respect to lead. Thus monitoring strategies and requirements for analytical performance vary considerably. The results of this survey suggest that protection of workers against the risk of exposure to lead at work is far from uniform across the European Union. Such disparity may also have implications on the requirements set at national level for laboratories measuring lead in blood and/or air. In the interest of harmonisation within the EU, further consideration should be given to the Annex II of the EC Directive 98/24, taking into account the suggestions for lower binding limit values for lead; this should include full guidelines for medical surveillance and requirements for laboratories should be issued.
- Dec 2005
The mechanisms behind the development of work-related trapezius pain are suggested to involve both peripheral and central components, but the specific contribution of alterations in muscle nociceptive and other substances is not clear. Female patients with chronic trapezius myalgia (N=19; TM) and female controls (N=20; CON) were studied at rest, during 20 min repetitive low-force exercise and recovery, and had their interstitial concentrations of potassium (K(+)), lactate dehydrogenase (LDH), interleukin-6 (IL-6) and collagen turnover determined in the trapezius muscle by the microdialysis technique. K(+) levels were at all time points higher in TM than in CON (P<0.0001). Baseline levels of LDH and IL-6 were similar in both groups. In response to exercise pain intensity, rated perceived exertion, and the concentrations of K(+), LDH and IL-6 increased significantly in both groups. [K(+)] immediately decreased to baseline levels in CON but remained elevated during the first 20 min of recovery in TM (P<0.01) whereafter it returned to baseline level. In all subjects taken together mean [K(+)] correlated negatively with pressure pain threshold of trapezius (P<0.001), positively with mean pain intensity VAS (P<0.001) and mean perceived exertion (P<0.001). Rises in muscle LDH and IL-6 as well as the anabolic ratio for collagen type I was not significantly different between groups. In conclusion, patients with chronic pain in the trapezius muscle had increased levels of interstitial potassium. This finding could be causally related to myalgia or secondary to pain due to deconditioned muscle or altered muscle activity pattern.
Risk related to contaminated soil is based on the oral intake of soil and dust among children. This exposure is a consequence of mouthing behaviour, which exposes children to whatever adheres to their hands or toys. This project compared hand exposure of children to lead following outdoor playground activities before and after an intervention. The intervention consisted of replacement of contaminated top soil from the most intensively used playground areas and coverage of bare soil with wood chips or grass. We included children from three kindergartens: one with very low levels of lead in soil and two kindergartens with an average lead concentrations in soil of 100-200 mg/kg. Measurements of lead in soil 5-7 weeks after interventions in two kindergartens verified that the interventions had effectively reduced the potential exposure to lead from the most intensively used areas of the playgrounds. The average lead concentration in soil after intervention was below 10 mg/kg. We found a good agreement between the average concentration of lead in soil and the amount of lead on the hands of the children. Thus, the exposure marker worked and had the advantage compared to a blood sample, that we could evaluate the effect of the interventions shortly after they were accomplished using a noninvasive method. The amount of lead on the hands measured in one of the two kindergartens after the remediation (0.73 microg) was not significantly different from the control kindergarten (0.58 microg). Children from the second kindergarten still had higher median exposures to lead (1.29 microg), but a large overlap existed with several children having lower amounts of lead on their hands than some children from the control kindergarten. Large variations in the amount of lead on hands were observed. Variations may reflect true differences in concentrations of lead in soil, but may also reflect different behavior and playing patterns. Our study demonstrated, that it was possible in a cost-effective way to reduce exposure significantly and to verify the effect with a sensitive, noninvasive method shortly after the interventions had been implemented..
Interleukin (IL)-6, which is released from muscle tissue during intense exercise, possesses important metabolic and probably anti-inflammatory properties. To evaluate the IL-6 response to low-intensity exercise, we conducted two studies: 1) a control study with insertion of microdialysis catheters in muscle and determination of interstitial muscle IL-6 response over 2 h of rest and 2) an exercise study to investigate the IL-6 response to 20 min of repetitive low-force exercise. In both studies, a microdialysis catheter (cutoff: 3,000 kDa) was inserted into the upper trapezius muscle of six male subjects, and the catheters were perfused with Ringer-acetate at 5 microl/min. Venous plasma samples were taken in the exercise study. The insertion of microdialysis catheters into muscle resulted in an increase in IL-6 from 8 +/- 0 to 359 +/- 171 and 484 +/- 202 pg/ml after 65 and 110 min, respectively (P < 0.001). Similarly, in the exercise study, IL-6 increased to 289 +/- 128 pg/ml after a 55-min rest (P < 0.001). During the subsequent repetitive low-force exercise, muscle IL-6 further increased to 1,246 +/- 461 pg/ml and reached 2,132 +/- 477 pg/ml after a 30-min recovery (all P < 0.001). In contrast to this, plasma IL-6 did not significantly change in response to exercise. We conclude that upper extremity, low-intensity exercise results in a substantial increase in IL-6 in the interstitium of the stabilizing trapezius muscle, whereas no change is seen for plasma IL-6.
Local muscle metabolic responses to repetitive low-force contractions and to intense static contractions were studied by microdialysis in humans. Microdialysate and electromyography (EMG) were sampled from the trapezius muscle, mixed venous blood samples were taken and perceived exertion was rated (0-9) before and during 20 min of standardized repetitive arm movement (REP), 60 min recovery (R1), and 10 min 90 degrees sustained arm position (SUS) at 20% maximum voluntary contraction, followed by 60 min recovery (R2) in six healthy male participants (28-33 years). Average muscle activity was 8 +/- 2% of EMGmax-RMS (mean +/-SEM) during REP and 22 +/- 5% of EMGmax-RMS during SUS. Perceived exertion increased from 0 to 3.2 +/- 0.5 during REP and from 0 to 8.5 +/- 0.3 during SUS. During REP interstitial muscle lactate increased from 2.1 +/- 0.2 to 2.9 +/- 0.2 mmol L(-1) (P < 0.001) and returned to the baseline level during R1, while dialysate [K+] increased from 3.8 +/- 0.2 to 4.7 +/- 0.2 mmol L(-1) (P < 0.002) and returned to 3.8 +/- 0.2 mmol L(-1) during R1. In contrast, plasma lactate and [K+] remained unchanged. During SUS interstitial muscle lactate increased from 2.3 +/- 0.2 to 3.3 +/- 0.3 mmol L(-1) (P < 0.003), increased further to 6.5 +/- 1.3 mmol L(-1) post-exercise (P < 0.001) and returned to baseline levels during R2. Dialysate [K+] increased from 3.9 +/- 0.2 to 4.6 +/- 0.2 mmol L(-1) (P < 0.05) and returned to baseline level during R2. Plasma lactate increased significantly during SUS whereas plasma [K+] was unchanged. During REP and SUS interstitial pyruvate was unchanged but increased in the post-exercise period proportional to the exercise intensity. The microdialysis technique was effective in revealing muscle metabolic events that were not found systemically. Furthermore, the trapezius muscle showed an anaerobic metabolism during low-force contraction, which could indicate inhomogeneous muscle activation.
Local metabolic changes are suggested to be involved in muscle pain development in humans. Nineteen women with chronic work-related trapezius myalgia (TM) and 20 healthy female controls (CON) were studied during baseline rest, 20 min repetitive low-force exercise, and 120 min recovery. Interstitial serotonin (5-HT), glutamate, lactate, pyruvate, and blood flow were determined by microdialysis in the trapezius muscle. Baseline pressure pain threshold (PPT) was lower (143+/-18 (TM) vs. 269+/-17 (CON)kPa) (mean+/-SEM), pain intensity (visual analogue scale, VAS) higher (33+/-5 vs. 2+/-1mm), muscle 5-HT higher (22.9+/-6.7 vs. 3.8+/-1.3 nmol/l), and glutamate higher (47+/-3 vs. 36+/-4 micromol/l) in TM than in CON (all P<0.05), whereas muscle blood flow was similar in groups. Furthermore, muscle pyruvate was higher (180+/-15 vs. 135+/-12 micromol/l) and lactate higher (4.4+/-0.3 vs. 3.1+/-0.3 mmol/l) in TM than in CON (P<0.001). In response to exercise, VAS and glutamate increased in both TM and CON (all P<0.05). In TM only, lactate and pyruvate increased significantly (P<0.02), whereas blood flow increased to similar levels in both groups. During the initial 20 min recovery period, blood flow remained increased in TM (P<0.005) whereas it decreased to baseline levels in CON. In conclusion, patients with chronic work-related TM have increased levels of muscle 5-HT and glutamate that were correlated to pain intensity (r=0.55, P<0.001) and PPT (r=-0.47, P<0.001), respectively. In addition, TM was associated with increased anaerobic metabolism, whereas a normal rise in blood flow was seen with exercise. These findings indicate that peripheral nociceptive processes are active in work-related TM.
- Oct 2004
An uncertainty budget was constructed for the measurement of ethanol in blood by headspace gas chromatography. The uncertainty budget, covering the analytical range of ethanol concentrations up to 3.00 g/kg, included analytical uncertainty components, traceability uncertainty components, and effects caused by interindividual variation in blood water content. The analytical combined standard uncertainty was estimated from duplicate measurements of real samples and included contributions from headspace recovery, variation between columns, injection, repeatability of analytical signals, and statistical uncertainty of the calibration function. The traceability uncertainty was estimated in a sub-budget based on information about the calibrator and about the preparation of the aqueous standards. Two uncertainty components depended on the interindividual variation in blood water content. First, it caused uncertainty on the density of the blood, and second, it had an effect on the gas phase concentration of ethanol when doing the headspace sampling. These effects as well as their covariance were included in the uncertainty budget. For fresh blood samples, the analytical uncertainty was the dominating uncertainty component, accounting for approximately 90% of the variance. For blood samples collected 100 h postmortem, the interindividual variation in blood water content was the largest uncertainty component. It was demonstrated that subtracting a "safety margin" of 0.1 g/kg from the results was sufficient to keep the risk of committing a type 1 error below 0.1% in ethanol concentrations ranging up to 2 g/kg for fresh blood samples. This risk was higher for postmortem blood samples because of the higher uncertainty of measurement, but still less than approximately 1.4%.
When measuring biomarkers in urine, volume (and time) or concentration of creatinine are both accepted methods of standardization for diuresis. Both types of standardization contribute uncertainty to the final result. The aim of the present paper was to compare the uncertainty introduced when using the two types of standardization on 24 h samples from healthy individuals. Estimates of uncertainties were based on results from the literature supplemented with data from our own studies. Only the difference in uncertainty related to the two standardization methods was evaluated. It was found that the uncertainty associated with creatinine standardization (19-35%) was higher than the uncertainty related to volume standardization (up to 10%, when not correcting for deviations from 24 h) for 24 h urine samples. However, volume standardization introduced an average bias of 4% due to missed volumes in population studies. When studying a single 24 h sample from one individual, there was a 15-20% risk that the sample was incomplete. In this case a bias of approximately 25% was introduced when using volume standardization, whereas the uncertainty related to creatinine standardization was independent of the completeness of the sample. The uncertainty of creatinine standardization is increased when studying single voids rather than 24 h urine samples. This is partially counteracted by the increased statistical power due to the increased number of samples for each individual. Furthermore, there is a considerable increase in convenience for the participants, when collecting small volumes rather than complete 24 h samples.
- Nov 2003
The aim of the Guide to Expression of Uncertainty in Measurement (GUM) is to harmonize the different practices for estimating and reporting uncertainty of measurement. Although there are clear advantages in having a common approach for evaluating uncertainty, application of the GUM approach to chemistry measurements is not straightforward. In the above commentary, Krouwer suggests that the GUM approach should not be applied to diagnostic assays, because (a) the quality of diagnostic assays is to low, and (b) the GUM uncertainty intervals are too narrow to predict the outliers that occasionally trouble these methods. Some of the examples presented by Krouwer are reviewed. Sodium measurements are modeled mathematically to illustrate the GUM approach to uncertainty. A standardized uncertainty evaluation process is presented. Modeling of sodium measurements demonstrates how the GUM uncertainty interval reflects the treatment of a bias: The width of the uncertainty interval varied depending on whether a correction for a calibrator lot bias was applied, but in both cases it was consistent with the distribution of measurement results. Expanding the uncertainty interval to include outliers runs counter to the definition of uncertainty. Used appropriately, the GUM uncertainty can be helpful in detecting outliers. In standardizing the uncertainty evaluation, the importance of the analytical imprecision and traceability was emphasized. It is problematic that manufacturers of commercial assays rarely inform about the uncertainty of the values assigned to the calibrators. As demonstrated by an example, external quality-assurance data may be used to estimate this uncertainty. The GUM uncertainty should be applied to measurements in laboratory medicine because it may actually support the forces that drive the work on improving the quality of measurement procedures. However, it is important that the GUM approach is made more manageable by standardizing the uncertainty evaluation procedure as much as possible. It is essential to focus on the traceability and uncertainty of calibrators and reagents supplied by manufacturers of assays. Information about uncertainty is necessary in the evaluation of the uncertainty associated with manufacturers' measurement procedures, and in general it may force manufacturers to increase their efforts in improving the metrologic and analytical quality of their products.
Systemic contact dermatitis is usually seen as flare-up of previous dermatitis or de novo dermatitis similar to allergic contact dermatitis. Although systemic contact dermatitis from medicaments is a well-established entity, the existence of clinically relevant systemic reactions to oral nickel exposure, in particular systemic reactions to nickel in the daily diet, remains controversial. Several studies have shown that oral exposure to nickel can induce systemic contact dermatitis in nickel-sensitive individuals. In most of these studies, however, the exposure dose of nickel used has been considerably higher than the nickel content in the normal daily diet. The aim of the current investigation was to study dose-response dependency of oral exposure to nickel. In a double-blind, placebo-controlled oral exposure trial, 40 nickel-sensitive persons and 20 healthy (non-nickel-sensitive) controls were given nickel sulfate hexahydrate in doses similar to and greater than the amount of nickel ingested in the normal Danish daily diet. The nickel content in urine and serum before and after oral exposure was measured to determine nickel uptake and excretion. The influence of the amount of nickel ingested on the clinical reactions to oral exposure and on nickel concentrations in serum and urine was evaluated. Among nickel-sensitive individuals, a definite dose-response dependency was seen, following oral exposure to nickel. 7 of 10 nickel-sensitive individuals had cutaneous reactions to oral exposure to 4.0 mg nickel, an amount approximately 10 times greater than the estimated normal daily dietary intake of nickel. 4 of 10 nickel-sensitive individuals had cutaneous reactions to 1.0 mg nickel, a dose which is close to the estimated maximum amount of nickel contained in the daily diet. 4 of 10 nickel-sensitive individuals reacted to 0.3 mg nickel or to the amount equivalent to that contained in a normal daily diet, and 1 of 10 reacted to a placebo. None of the 20 healthy controls had cutaneous reactions to 4.0 mg nickel or to a placebo. Prior to oral exposure, there was no measurable difference in the amount of nickel in the urine or serum of nickel-sensitive persons and healthy controls. Following the oral challenge, the nickel content in the urine and serum of both nickel-sensitive and healthy control individuals was directly related to the dose of nickel ingested.
- Feb 2003
The aims of this study were to elucidate to what extent storage and repeated freezing and thawing influenced the concentration of creatinine in urine samples and to evaluate the method for determination of creatinine in urine. The creatinine method was based on the well-known Jaffe's reaction and measured on a COBAS Mira autoanalyser from Roche. The main findings were that samples for analysis of creatinine should be kept at a temperature of -20 degrees C or lower and frozen and thawed only once. The limit of detection, determined as 3 x SD of 20 determinations of a sample at a low concentration (6.1 mmol/L), was 0.3 mmol/L, and the recovery of a certified reference material was 97%. The relative precision at 3.15 mmol/L was 2.3%. It was concluded that the method is appropriate for measurement of urinary creatinine.
The different scoring methods used by eight European External Quality Assessment Schemes (EQASs) for occupational and environmental laboratory medicine were compared to develop suitable quality specifications as a step toward harmonization. Real results for blood lead and serum aluminum assays, reported by participants in Italian and United Kingdom EQASs, were evaluated according to individual scheme scoring criteria. The same results were then used to produce z scores using scheme-based between-laboratory SDs as the estimate of variability to determine whether simple performance-derived quality specifications produced better agreement among schemes. The schemes gave conflicting assessments of participants' performance, and participants judged to be successful by one scheme could be defined as performing inadequately by another. An approach proposed by Kenny et al. (Scand J Clin Lab Invest 1999;59:585), which uses clinical inputs to set targets for analytical imprecision, bias, and total error allowable, was then used to elaborate quality specifications. We suggest that the CLIA '88 recommendations for blood lead (+/- 40 micro g/L or +/- 10% of the target concentration, whichever is the greater) could be used as a quality specification, although a revision to +/- 30 micro g/L or +/- 10% is recommended. For serum aluminum, a suitable quality specification of +/- 5 micro g/L or +/- 20% of the target concentration, whichever is the greater, is suggested. These specifications may be used to compare laboratory performance across schemes.
- Jun 2002
The comparison of analytical results calls for validation of the assays used, i.e. for the documentation of accuracy (trueness and precision), linearity and specificity. In addition, there is a growing demand for evaluation and documentation of traceability and uncertainty of analytical results. However, models for establishing the traceability and uncertainty of immunoassay results are lacking. Sandwich enzyme-linked immunosorbent assays (ELISAs) were developed for determination of the human cytokines interleukin-4 (IL-4), interleukin-5 (IL-5), interferon-y (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). The accuracy of each of the assays was evaluated in the ranges of 1-15 microg/l (IL-4), 0.001-1 microg/l (IL-5), 0.5-2.5 microg/l (IFN-T) and 0.14-2.2 microg/l (TNF-alpha). Other evaluated performance characteristics were the limit of detection (LOD), immunological specificity, and robustness. Traceability was ensured by the use of World Health Organization International Standards (WHO IS). An uncertainty budget, which combined the contribution from all known uncertainty components, was established for each cytokine ELISA. The between-run relative analytical standard deviation (RSDA) of the assessed ELISAs was found to be in the range of 11-18%, except for IL-5 where RSDA increased at decreasing concentrations. The LOD was 0.12 microg/l, 0.0077 microg/l, 0.0069 microg/l and 0.0063 microg/l for IL-4, IL-5, IFN-gamma and TNF-alpha, respectively. Traceability to the WHO IS was established for each of the cytokines. The combined relative standard uncertainty (U(result)/C(result)) was 28%, 22-62%, 28% and 24% for the IL-4, IL-5, IFN-gamma and TNF-alpha results, respectively. The major contributions to uncertainty came from the relative analytical standard deviation and from the uncertainty of the mass concentration of the WHO IS. The uncertainty of the WHO IS was not stated in the accompanying certificate and was evaluated by other means. The largest sources of uncertainty were located outside our laboratory. This means that the possibilities to improve the reliability of the results produced by the ELISAs are very limited. The task of evaluating measurement uncertainty would be much easier if producers of international reference standards reported the uncertainty of the value of standards. The model for evaluating uncertainty presented in this paper is applicable to other types of assays and to most analytical methods.
- Nov 2001
There is a growing pressure on clinical chemistry laboratories to conform to quality standards that require the evaluation and expression of the uncertainty of results of measurement. Nevertheless, there is some reluctance to accept the uncertainty concept in the analytical community due to difficulty in evaluating uncertainty in practice. For example, often the uncertainty of some uncertainty components is not known very well in clinical chemistry measurements, such as those associated with matrix effects or with the values of the calibrators. Moreover, it is not clear how to interpret uncertainty in relation to diagnostic criteria, reference ranges and other decision limits in clinical chemistry practice. Hence, the value of reporting the uncertainty of the measurement result is not obvious. In this paper it is suggested a relatively simple, logical procedure for evaluating measurement uncertainty based on the principles in the Guide for the Expression of Uncertainty of Measurement (GUM). The measurement process is partitioned into elements that are well known to the analyst, namely sampling, calibration, and analysis. The corresponding model function expresses the result of a measurement as the value obtained by the analytical procedure multiplied by the correction factors for sampling bias, for bias caused by the calibrators, and for other types of bias. Under normal conditions, when the measurement procedure is validated and corrected for all known bias, the expected value of each correction factor is one. The uncertainty that remains with regard to sampling, manufacturing of calibrators and other types of bias is combined with the analytical imprecision to yield a combined uncertainty of a result of measurement. The advantages of this approach are: (i) Data from the method validation, internal quality control and from participation in external quality control schemes can be used as input in the uncertainty evaluation process. (ii) The partition of the measurement into well-defined tasks highlights the different responsibilities of the clinical chemistry laboratory and of the manufacturer of reagents and calibrators. (iii) The approach can be used to harmonize the uncertainty evaluation process, which is particularly relevant for laboratories seeking accreditation under ISO 17025. The application of the proposed model is demonstrated by evaluating the uncertainty of a result of a measurement of prolactin in human serum. In the example it is shown how to treat the uncertainty associated with a calibrator supplied with a commercial analytical kit, and how to evaluate the uncertainty associated with matrix effects.
- Dec 2000
A competitive ELISA with an inhibition step for the determination of serum keratan sulphate (KS), was validated using bovine corneal KS as standard. The method was shown to be in statistical control. The recovery was 85% (S.D.=2.2%), hence the obtained results had to be corrected. The limit of detection (LOD) was 1.4μgml−1. Intra-assay CV was 3.0% (n=15) for samples used for method evaluation and 6.0% (n=18) for serum samples. Inter-assay CV was 7.0% for high KS level samples (CKS=31.2μgml−1) and 16.0% for low KS level samples (CKS=5.9μgml−1) based on the S.D.y/x from the method evaluation function and 10% (high KS level) and 16% (low KS level) based on serum samples. Validation of the method was performed using the serum samples from 102 healthy individuals. There was a statistical difference in serum KS levels between men and women, but no age related differences. Tentative biological reference intervals for men and women were established. It was also shown that due to the large between-subject variability in KS levels, the preferable monitoring strategy is to use individuals as their own controls where possible.
- Nov 2000
The present study aimed at evaluating the effects of daily repeated exposures to low cobalt or chromate concentrations on the hands of patients with hand eczema and cobalt or chromate allergy. For 2 weeks, the patients immersed a finger for 10 min daily into the appropriate metal salt solution in water. During the 1st week, this was a 10 or 50 mg/l cobalt concentration or a 10 mg/l chromate concentration, and, during the 2nd week, a 100 or 200 mg/l cobalt concentration or a 100 mg/l chromate concentration. This regimen elicited a flare of hand eczema only in the chromate-exposed chromate-sensitive patients. During the exposure period, accumulation of cobalt or chromate in the nail was demonstrated. Standardization of chemical methods of quantification of skin exposure to allergens, combined with experimental exposure studies in patients with specific contact allergy, will increase the possibility of providing evidence-based medicine in the area of allergic contact dermatitis in the future.
- Jul 2000
Exposure to nickel is a major cause of allergic contact dermatitis which is considered to be an inflammatory response induced by antigen-specific T cells. Here we describe the in vitro analysis of the nickel-specific T-cell-derived cytokine response of peripheral blood mononuclear cells from 35 nickel-allergic and 30 non-nickel-allergic individuals. Peripheral blood mononuclear cells were stimulated with 10(-4) and 10(-5) mol/l NiSO4 for 6 days and then additionally with ionomycin and phorbol myristate acetate for 24 h. Culture supernatants were analysed for interleukin-4 (IL-4), IL-5, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) by quantitative ELISA. The analysis showed that the synthesis of IL-4 and IL-5 but not of IFN-gamma or TNF-alpha was significantly higher in the nickel-allergic individuals. The finding of preferential synthesis of Th2 cytokines was somewhat of a surprise, since previous studies have suggested a Th1 response in nickel-mediated allergic contact dermatitis. Subsequently, the nickel-allergic individuals were randomized to experimental exposure to nickel or vehicle in a double-blind design. A daily 10-min exposure of one finger to 10 ppm nickel solution for 1 week followed by 100 ppm for an additional week evoked a clinical response of hand eczema in the nickel-exposed group. Blood samples were drawn on days 7 and 14 after the start of this exposure to occupationally relevant concentrations of nickel. No statistically significant differences were observed in the nickel-induced in vitro cytokine response during the exposure period. Our results indicate the possibility that IL-4 and IL-5 are involved in the pathogenesis of nickel-mediated contact dermatitis.
Abstract Exposure to nickel is a major cause of allergic contact dermatitis which is considered to be an inflammatory response induced by antigen-specific T cells. Here we describe the in vitro analysis of the nickel-specific T-cell-derived cytokine response of peripheral blood mononuclear cells from 35 nickel-allergic and 30 non-nickel-allergic individuals. Peripheral blood mononuclear cells were stimulated with 10–4 and 10–5 mol/l NiSO4 for 6 days and then additionally with ionomycin and phorbol myristate acetate for 24 h. Culture supernatants were analysed for interleukin-4 (IL-4), IL-5, interferon-γ (IFN-γ) and tumour necrosis factor-α (TNF-α) by quantitative ELISA. The analysis showed that the synthesis of IL-4 and IL-5 but not of IFN-γ or TNF-α was significantly higher in the nickel-allergic individuals. The finding of preferential synthesis of Th2 cytokines was somewhat of a surprise, since previous studies have suggested a Th1 response in nickel-mediated allergic contact dermatitis. Subsequently, the nickel-allergic individuals were randomized to experimental exposure to nickel or vehicle in a double-blind design. A daily 10-min exposure of one finger to 10 ppm nickel solution for 1 week followed by 100 ppm for an additional week evoked a clinical response of hand eczema in the nickel-exposed group. Blood samples were drawn on days 7 and 14 after the start of this exposure to occupationally relevant concentrations of nickel. No statistically significant differences were observed in the nickel-induced in vitro cytokine response during the exposure period. Our results indicate the possibility that IL-4 and IL-5 are involved in the pathogenesis of nickel-mediated contact dermatitis.
A atomic absorption spectrometry method for the determination of nickel in finger nails and in the upper layer of the skin (stratum corneum) was developed, validated and applied in an experimental study on nickel allergic patients and non-nickel allergic controls. The relative intermediate precision (including between-day variation) was in the range 5.5–12%, and the limit of detection was 0.2 μg nickel per g nail and 1 ng nickel per skin sample, respectively. The baseline levels of nickel in nails were approximately 1.58 μg per g nail, which is comparable to previously reported reference values. No differences could be observed between patients and controls. Both nickel in nails and in skin samples increased significantly when low nickel doses were applied to fingers and the forearm, respectively. This suggests that nickel in nails and in skin samples may be relevant in characterizing occupational skin exposure to nickel.
Cast iron products are alloyed with small quantities of manganese, and foundry furnacemen are potentially exposed to manganese during tapping and handling of smelts. Manganese is a neurotoxic substance that accumulates in the central nervous system, where it may cause a neurological disorder that bears many similarities to Parkinson's disease. The aim of the study was to investigate the sources and levels of manganese exposure in foundry furnacemen by a combined measuring of blood-manganese (B-Mn) and manganese in ambient air (air-Mn). During a period of 16 months, Air-Mn and B-Mn (denoted 'exposure values') were measured involving 24 furnacemen employed in three small size foundries and 21 scrap recycling workers from one plant. In the study period, 18 furnacemen had B-Mn measured 3-4 weeks after decreasing or stopping exposure (denoted 'post-exposure values'). The reference group for the B-Mn measurements consisted of 90 Danish male subjects. Furnacemen who work in insufficiently ventilated smelting departments inhale, absorb, and retain significant amounts of manganese in their blood (approx. 2.5-5 microg/l above reference values) despite a generally low measured airborne level of manganese fumes (0.002-0.064 mg/m(3)). The 'exposure values' compared with 'post-exposure values' revealed a significant decrease in the B-Mn (on average 3.7 microg/l) level of the most exposed furnacemen. Two persons in our study were suspected of suffering clinically subacute manganese intoxication as both had B-Mn levels beyond the normal limit (25 and 29 microg/l, respectively). The potential problem disappeared completely after cessation of exposure, and the B-Mn levels decreased to 9.4 and 14.1 microg/l, respectively. Risk assessment based on combined measurements of B-Mn and air-Mn seems to be valid in the interpretation of workers' hazard. Our study indicates that B-Mn may be a valuable parameter for estimating recent exposure (within 1-2 weeks). However, more knowledge is needed about the B-Mn level and its relation to neurological symptoms.
The uncertainty of the Kjeldahl method for determination of nitrogen in insulin was evaluated according the procedure described in the Guide to the Expression of Uncertainty in Measurement. The relative standard uncertainty of the method was found to be 0.19%, compared to the relative intermediate precision experimentally found to be 0.085%. The uncertainty components were organized in Tables, which allowed an easy overview and evaluation. The largest contribution to the uncertainty came from volumetric equipment. Systematic uncertainty budgets such as the design presented here facilitate the uncertainty evaluation process and makes it easier to compare uncertainty evaluations performed by different analysts.
- Nov 1999
We studied the effects of repeated daily exposure to low nickel concentrations on the hands of patients with hand eczema and nickel allergy. The concentrations used were chosen to represent the range of trace to moderate occupational nickel exposure. The study was double-blinded and placebo controlled. Patients immersed a finger for 10 min daily into a 10-p.p.m. nickel concentration in water for the first week, and during the second week into a 100-p.p.m. nickel concentration. This regimen significantly increased (P = 0.05) local vesicle formation and blood flow (P = 0.03) as compared with a group of patients who immersed a finger into water. The nickel concentrations used also provoked significant inflammatory skin changes on sodium lauryl sulphate (SLS)-treated forearm skin of the patients, whereas inflammatory skin changes were not observed in healthy volunteers without hand eczema and nickel allergy, either on normal or on SLS-treated forearm skin. The present study strongly suggests that the changes observed were specific to nickel exposure. Standardized methods to assess trace to moderate nickel exposure on the hands, and the associated effects in nickel-sensitized subjects, are needed.
- Oct 1999
This study is a part of the Biological Risk Assessment of Human Metal Sensitisation (BRAHMS) project with the aim of elucidating clinical and physiological effects of repeated exposures to low concentrations of metal allergens. Nickel allergic individuals (n = 35) with hand eczema and healthy controls (n = 30) were included in the study. Both groups had similar levels of nickel in urine, while the level of nickel in serum was significantly lower in nickel allergic individuals compared to controls. Nickel allergic individuals had a significantly lower intake of nickel-rich food items (chocolate, nuts, beans, porridge oats). Serum nickel levels correlated with intake of these foods, suggesting that the difference in serum nickel levels was caused by differences in dietary nickel intake.
- Sep 1999
A high performance liquid chromatography (HPLC) method with fluorescence detection including an on-line purification was established for determination of catecholamines in human urine. The method was evaluated using samples of pooled urine spiked with catecholamines and validated for measurements of catecholamines in urine of healthy individuals in a field study. The laboratory method evaluation study showed that the recovery of the method was 0.82 (confidence interval (CI): 0.79–0.86) and 0.92 (CI: 0.89–0.95) for noradrenaline and adrenaline, respectively. Thus, correction factors of 0.82−1 and 0.92−1 were applied to correct the measurement results for this systematic effect. Furthermore, an uncertainty budget was generated for the analytical method using the BIPM-approach recommended by the International Organization for Standardization. The relative uncertainty of the method was estimated to be 10–12%, which was consistent with the observed relative variability found in the method evaluation. The method was evaluated in accordance with EURACHEM Guidance Document No 1 concerning accreditation for chemical laboratories with respect to accuracy and precision. The field study showed that the standard deviation of the method was sufficiently low to distinguish between persons working with two different processes of garbage collection, i.e. collection using four wheeled containers versus collection using bins.
A summary is given of the main strategies that can be used to obtain high quality results in the determination of metals in clinical chemistry. The trends in quality assurance of metal analyses are discussed.
Molybdenum creatinine levels in urine were measured in 128 Danish inhabitants by ICP-MS in order to establish reference intervals of molybdenum in urine for the Danish population as a part of the EURO-TERVIHT project (Trace Element Reference Values in Human Tissues). The Mo concentration was determined using the isotopes 95Mo and 98Mo. The values measured based on 98Mo were about 2% lower than those calculated using 95Mo, a negligible difference in the context of reference values. The limit of detection was 0.2 microgram l-1, the precision was 8.6% and the recovery of added NIST 1643c certified reference material was 94%. The distribution of the data, with and without correction for creatinine concentration, was long-normal. The mean concentration measured was 42.5 micrograms l-1, (3.89 micrograms Mo mmol-1 creatinine) using 95Mo and 41.5 micrograms l-1 (3.81 micrograms Mo mmol-1 creatinine) using 98Mo, with the 95% parametric reference intervals 10.0-124.0 micrograms l-1 (0.89-11.50 micrograms Mo mmol-1 creatinine) and 9.6-122.6 micrograms l-1 (0.84-11.47 micrograms Mo mmol-1 creatinine), respectively. The difference between men and women reached the level of significance only after the values were corrected for the creatinine concentration. There was no influence of age on the Mo concentration. Specific effects of different food and beverage intakes could not be demonstrated, with the exception of a positive correlation between butter consumption and Mo concentration.
- Nov 1997
Two candidate reference materials for chromate in cement were produced in the DANREF network and certified in an interlaboratory study. Fifteen laboratories participated in the interlaboratory study and six different analytical methods were used. The certified values were estimated as the consensus mean of laboratory mean values (outliers excluded). Only results from laboratories using methods relying on chromate speciation were accepted. The certified values (+/- 95% confidence limits) were 0.678 (+/- 0.075) mg CrVI kg-1 dry cement for the low level and 6.04 (+/- 0.28) mg CrVI kg-1 dry cement for the high level. Methods based on total chromium determination gave on average results that were 6.5% higher (both levels). However, the difference between speciation and non-speciation results was significant at the high concentration level only.
- Oct 1997
This study is part of the EURO-TERVIHT project (Trace Element Reference Values in Human Tissues) which aims at establishing reference intervals for trace elements in blood, urine and other human tissues. In this study reference intervals (0.05-0.95 fractiles) were estimated for lead in blood (105-529 nmol/l for men, 80-340 nmol/l for women), manganese in blood (100-271 nmol/l) and arsenic in urine (36-541 nmol/l for men, 21-475 nmol/l for women). Upper reference limits (0.95 fractile) were established for chromium in urine (13 nmol/l), nickel in urine (52 nmol/l) and cobalt in urine (23 nmol/l for men, 31 nmol/l for women). The reference group was a Danish subpopulation (n = 189), age 40-70 years. The influence of gender, age, health status parameters, nutrition and various lifestyle factors was investigated. Urinary arsenic and blood lead levels were found to be higher for men than for women. Arsenic levels also increased with age up to 60 years, and then decreased. Alcohol intake lead to increased arsenic levels in urine as well as blood lead levels. Urinary nickel levels were higher in persons frequently eating porridge and porridge oats.
- Mar 1996
The major sources of uncertainty of a method for determination of Pb in whole blood by atomic absorption spectrometry were identified. The combined uncertainty was compared to the experimentally determined variation and a satisfactory agreement was found, indicating that no significant sources of uncertainty have been overlooked and that the method is in a state of statistical control. The findings suggest that the major source of uncertainty at low concentrations are random fluctuations (noise) of the atomic signal. Therefore, if improvement of the method performance is needed, only actions directed towards enhancing the signal-to-noise ratio are suitable.
- Feb 1996
Participation in proficiency testing schemes is generally recognized as an important part of quality control in analytical chemistry. The design and conduct of proficiency testing schemes is therefore a matter of great importance. A proficiency testing scheme should: a) cover a broad concentration range of the substance of interest; b) enable the detection and estimation of each laboratory's systematic errors; c) enable estimation of each laboratory's random error; d) provide each laboratory with a rank or score, and e) present the evaluation of each round to the participating laboratories in a comprehensible way, e.g. in a report with carefully designed text, tables and figures. This paper presents the design of the Danish external quality assessment scheme (DEQAS), which is based on the method evaluation function concept.