[Show abstract][Hide abstract] ABSTRACT: This field study evaluated the level of muscular, cardiorespiratory and thermal strain of mast and pole workers. We measured the muscular strain using electromyography (EMG), expressed as a percentage in relation to maximal EMG activity (%MEMG). Oxygen consumption (VO2) was indirectly estimated from HR measured during work and expressed as a percentage of maximum VO2 (%VO2max). Skin and deep body temperatures were measured to quantify thermal strain. The highest average muscular strain was found in the wrist flexor (24 ± 1.5%MEMG) and extensor (21 ± 1.0%MEMG) muscles, exceeding the recommendation of 14%MEMG. Average cardiorespiratory strain was 48 ± 3%VO2max. Nearly half (40%) of the participants exceeded the recommended 50%VO2max level. The core body temperature varied between 36.8°C and 37.6°C and mean skin temperature between 28.6°C and 33.4°C indicating possible occasional superficial cooling. Both muscular and cardiorespiratory strain may pose a risk of local and systemic overloading and thus reduced work efficiency. Thermal strain remained at a tolerable level.
[Show abstract][Hide abstract] ABSTRACT: Typical military tasks include load carriage, digging, and lifting loads. To avoid accumulation of fatigue, it is important to know the energy expenditure of soldiers during such tasks. The purpose of this study was to measure cardiorespiratory responses during military tasks in field conditions. Unloaded (M1) and loaded (M2) marching, artillery field preparation (AFP), and digging of defensive positions (D) were monitored. 15 conscripts carried additional weight of military outfit (5.4 kg) during M1, AFP, and D and during M2 full combat gear (24.4 kg). Absolute and relative oxygen uptake (VO2) and heart rate (HR) of M1 (n = 8) were 1.5 ± 0.1 L min(-1), 19.9 ± 2.7 mL kg(-1) min(-1) (42 ± 7% VO2max), and 107 ± 8 beats min(-1) (55 ± 3% HRmax), respectively. VO2 of M2 (n = 8) was 1.7 ± 0.2 L min(-1), 22.7 ± 3.4 mL kg(-1) min(-1) (47 ± 6% VO2max) and HR 123 ± 9 beats min(-1) (64 ± 4% HRmax). VO2 of AFP (n = 5) and D (n = 6) were 1.3 ± 0.3 L min(-1), 18.0 ± 3.0 (37 ± 6% VO2max), and 1.8 ± 0.4 L min(-1), 24.3 ± 5.1 mL kg(-1) min(-1) (51 ± 9% VO2max), respectively. Corresponding HR values were 99 ± 8 beats min(-1) (50 ± 3% HRmax) and 132 ± 10 beats min(-1) (68 ± 4% HRmax), respectively. The mean work intensity of soldiers was close to 50% of their maximal aerobic capacity, which has been suggested to be maximal limit of intensity for sustained work.
[Show abstract][Hide abstract] ABSTRACT: Objective. To determine the association between intensity of information and communication technology (ICT) usage and quality of sleep in school-aged children during a school week. Methods. In all 61 subjects, 10-14 years of age, a quasiexperimental laboratory study where criterions for inclusion were absence of prior medical condition and duration of ICT use. A portable device (Holter monitor) was used to measure heart rate variability (HRV) over a 24-hour period, while activity diary was used to record in 15-minute intervals ICT use and sleep and wake up time. Low and high ICT user groups were formed according to their intensity of ICT use. Statistical analysis was done with two independent samples tests and factorial ANCOVA. Results. The higher ICT users showed a lower sleep time standard deviation of normal to normal interval (SDNN) measures in comparison to the low ICT users. Conclusion. The intensive ICT use was associated with poorer quality of sleep indicated by physiological measures among children and adolescents. Knowing the crucial role of healthy sleep in this age, the results are reason for concern.
[Show abstract][Hide abstract] ABSTRACT: The aim of this cross-sectional study was to determine the association between lowered endothelial function measured by peripheral arterial tonometry (PAT) and cardio-metabolic risk factors. The study population consisted of Finnish municipal workers who were at risk of diabetes or cardiovascular disease and who had expressed a need to change their health behaviour.
A total of 312 middle-aged municipal workers underwent a physical medical examination and anthropometry measurements. Levels of total cholesterol, HDL cholesterol, triglycerides, fasting glucose, glycated haemoglobin, and high sensitivity C-reactive protein were taken from the blood samples. PAT measured the increase in digital pulse volume amplitude during reactive hyperemia, and the index of endothelial function, F-RHI, was defined as the ratio of post-deflation amplitude to baseline amplitude.
In the linear regression model, male sex was associated with lower F-RHI. In sex-adjusted linear regression models, each of the variables; waist circumference, fasting glucose, glycated hemoglobin, triglycerides, body fat percentage, body mass index, current smoking, and impaired fasting glucose or diabetes were separately associated with lower F-RHI, and HDL cholesterol and resting heart rate were associated with higher F-RHI.HDL cholesterol, sex, body mass index, and current smoking entered a stepwise multivariable regression model, in which HDL cholesterol was associated with higher F-RHI, and smoking, male sex and body mass index were associated with lower F-RHI. This model explains 28.3% of the variability in F-RHI.
F-RHI is associated with several cardio-metabolic risk factors; low level of HDL cholesterol, male sex, overweight and smoking being the most important predictors of a lowered endothelial function. A large part of variation in F-RHI remains accounted for by unknown factors.
[Show abstract][Hide abstract] ABSTRACT: Cardiac pacemakers are known to be susceptible to strong electromagnetic fields (EMFs). This in vivo study investigated occurrence of electromagnetic interference with pacemakers caused by common environmental sources of EMFs.
Eleven volunteers with a pacemaker were exposed to EMFs produced by two mobile phone base stations, an electrically powered commuter train, and an overhead high voltage transmission lines. All the pacemakers were programmed in normal clinically selected settings with bipolar sensing and pacing configurations.
None of the pacemakers experienced interference in any of these exposure situations. However, often it is not clear whether or not strong EMFs exist in various work environments, and hence an individual risk assessment is needed.
Modern pacemakers are well shielded against external EMFs, and workers with a pacemaker can most often return to their previous work after having a pacemaker implanted. However, an appropriate risk assessment is still necessary after the implantation of a pacemaker, a change of its generator, or major modification of its programming settings.
[Show abstract][Hide abstract] ABSTRACT: The hypocholesterolemic effect of plant stanol ester consumption has been studied extensively, but its effect on cardiovascular health has been less frequently investigated. We studied the effects of plant stanol esters (staest) on arterial stiffness and endothelial function in adults without lipid medication.
Ninety-two asymptomatic subjects, 35 men and 57 women, mean age of 50.8+/-1.0 years (SEM) were recruited from different commercial companies. It was randomized, controlled, double-blind, parallel trial and lasted 6 months. The staest group (n=46) consumed rapeseed oil-based spread enriched with staest (3.0 g of plant stanols/d), and controls (n=46) the same spread without staest. Arterial stiffness was assessed via the cardio-ankle vascular index (CAVI) in large and as an augmentation index (AI) in peripheral arteries, and endothelial function as reactive hyperemia index (RHI). Lipids and vascular endpoints were tested using analysis of variance for repeated measurements.
At baseline, 28% of subjects had a normal LDL cholesterol level (<=3.0 mmol/l) and normal arterial stiffness (<8). After the intervention, in the staest group, serum total, LDL, and non-HDL cholesterol concentrations declined by 6.6, 10.2, and 10.6% compared with controls (p<0.001 for all). CAVI was unchanged in the whole study group, but in control men, CAVI tended to increase by 3.1% (p=0.06) but was unchanged in the staest men, thus the difference in the changes between groups was statistically significant (p=0.023). AI was unchanged in staest (1.96+/-2.47, NS) but increased by 3.30+/-1.83 in controls (p=0.034) i.e. the groups differed from each other (p=0.046). The reduction in LDL and non-HDL cholesterol levels achieved by staest was related to the improvement in RHI (r=-0.452, p=0.006 and -0.436, p=0.008).
Lowering LDL and non-HDL cholesterol by 10% with staest for 6 months reduced arterial stiffness in small arteries. In subgroup analyses, staest also had a beneficial effect on arterial stiffness in large arteries in men and on endothelial function. Further research will be needed to confirm these results in different populations.Trial registration: Clinical Trials Register # NCT01315964.
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVES: To investigate cardiorespiratory and inflammatory responses in male workers following exposure to welding fumes and airborne particles in actual workplace conditions. MATERIALS AND METHODS: We measured blood leukocytes and their differential counts, platelet count, hemoglobin, sensitive C-reactive protein, fibrinogen, E-selectin, IL-(interleukin)1β, IL-6, IL-8, tumor necrosis factor alpha (TNF-α) and endothelin-1 in blood samples of twenty workers before and after their working day. We also studied peak expiratory flow (PEF), forced expiratory volume in one second (FEV1), and exhaled nitric oxide (NO). We assessed heart rate variability (HRV) by obtaining 24-hour ambulatory electrocardiograms. RESULTS: The total blood leukocytes and neutrophils increased after the work shift, whereas IL-1β and E-selectin decreased significantly. There were no statistically significant changes in exhaled NO, FEV1, PEF or HRV. CONCLUSION: Occupational exposure to welding fumes and particles caused a slight, acute inflammatory effect estimated by an increase in the blood leukocyte and neutrophil values and a decrease in the IL-1β and E-selectin values, but no changes in the pulmonary function (exhaled NO, FEV1, PEF) or HRV during the working day were observed.
International Journal of Occupational Medicine and Environmental Health 05/2013; · 1.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Occasionally firefighters need to perform very heavy bouts of work, such as smoke diving or clearing an accident site, which induce significant muscle fatigue. The time span for muscular recovery from such heavy work is not known. The purpose of this study was to evaluate firefighters' force-, neural-, metabolic-, and structural-related recovery after task-specific heavy work in the heat. Fifteen healthy firefighters (14 males and 1 female) performed a 20-min heavy work bout that simulated smoke diving and the clearance of an accident site at 35 °C. After the work, muscular recovery was evaluated by wrist flexion maximal voluntary contraction (MVC), average electromyography during MVC and during 10%MVC, rate of force production, motor response and stretch reflex responses, muscle oxygen consumption and oxygenation level, and wrist flexor muscle pennation angle. Recovery was followed for 4 h. Each of the 12 measured parameters changed significantly (p < 0.05) from those at baseline during the follow-up. Muscle oxygen consumption and the wrist flexor pennation angle remained elevated throughout the follow-up (oxygen consumption baseline, 12.9 ± 1.7 mL O2·min(-1)·(100 g)(-1); 4-h value, 17.5 ± 1.6 mL O2·min(-1)·(100 g)(-1); p < 0.05 and pennation angle baseline, 15.7 ± 0.8°; 4-h value, 17.8 ± 0.8°; p < 0.05). Muscle reoxygenation rate was elevated for up to 2 h (baseline, 2.3 ± 0.4 μmol·L(-1)·min(-1); 2-h value, 3.4 ± 0.4 μmol·L(-1)·min(-1); p < 0.05). The other 9 parameters recovered (were no longer significantly different from baseline) after 20 to 60 min. We concluded that the recovery order in main components of muscle function from fastest to slowest was force, neural, metabolic, and structural.
[Show abstract][Hide abstract] ABSTRACT: Earlier studies have suggested associations between metabolic factors and musculoskeletal pain or disorders. We studied the associations of obesity, lipids, other features of the metabolic syndrome and adipokines (adiponectin, leptin, resistin, visfatin) with upper extremity pain in a clinical population with incipient upper extremity soft tissue disorders (UESTDs).
A cross-sectional study.
Primary healthcare (occupational health service) with further examinations at a research institute.
Patients (N=163, 86% were women) seeking medical advice in the occupational health service due to incipient upper extremity symptoms with symptom duration of <1 month were referred for consultation to the Finnish Institute of Occupational Health from Spring 2006 to Fall 2008. We included all actively working subjects meeting diagnostic criteria based on physical examination. We excluded subjects meeting predetermined conditions.
Pain intensity was assessed with visual analogue scale and dichotomised at the highest tertile (cut-point 60).
Obesity (adjusted OR for high waist circumference 2.9, 95% CI 1.1 to 7.3), high-density lipoprotein cholesterol (OR 3.9, 95% CI 1.4 to 10.1 for low level) and triglycerides (OR 2.6, 95% CI 1.0 to 6.8 for high level) were associated with pain intensity. Of four adipokines studied, only visfatin was associated with upper extremity pain (adjusted OR 1.4, 95% CI 1.0 to 2.1 for 1SD increase in level).
Abdominal obesity and lipids may have an impact on pain intensity in UESTDs. They may intensify pain through proinflammatory pain-modifying molecular pathways or by causing soft tissue pathology and dysfunction of their supplying arteries. Of four adipokines studied only one (visfatin) was associated with pain intensity. In the future, further studies are required to better understand the relationship between metabolic factors and UESTDs.
BMJ Open 01/2013; 3(8):e003036. · 1.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: For decades in Finland, intensive population strategies and preventive activities have been used to lower the risk of atherosclerotic coronary heart disease (CHD). Lifestyle changes, with the emphasis on diet, play an important role in preventive strategies. The aim of this study was to evaluate arterial stiffness and endothelial function in asymptomatic free-living adults and to relate the results to CHD risk factors and lifestyle habits with the emphasis on diet.
Ninety-four asymptomatic participants were recruited by advertisements in four large companies and two research institutes employing mainly office workers. Arterial stiffness was assessed as the cardio-ankle vascular index in large arteries, and endothelial function as the reactive hyperemia index with peripheral arterial tonometry. The systematic Cardiovascular Risk Estimation (SCORE) was calculated.
The data was collected in the spring of 2011. Anthropometric, dietary, and lipid data was available from 92 participants, blood pressure from 85 and vascular measurements from 86-88 subjects (38% males; 62% females; mean age of all 51). The majority (72%) had an elevated low density lipoprotein (LDL) cholesterol concentration and over half were overweight or obese. SCORE stated that 49% of the participants had a moderate risk of cardiovascular disease. When compared to general recommendations, half of the participants had too high intake of total fat and in 66% the consumption of saturated fat was too high. In contrast, the intake of carbohydrates was too low in 90% of the participants and for fiber 73% were below recommendations. There was evidence of borderline or increased arterial stiffness in 72% of the participants and endothelial function was impaired in 8%. Arterial stiffness was associated with LDL cholesterol concentration (p = 0.024), dietary cholesterol intake (p = 0.029), and SCORE (p < 0.001).
In a cross-sectional study of asymptomatic middle-aged participants, the half had a moderate risk for cardiovascular diseases manifested as increased arterial stiffness, elevated LDL cholesterol concentration, and poor dietary habits. The new observation that arterial stiffness was associated with dietary cholesterol intake and SCORE emphasizes the urgency of adequate lifestyle and dietary interventions to prevent future coronary events even in asymptomatic participants.
Clinical Trials Register # NCT01315964.
[Show abstract][Hide abstract] ABSTRACT: Blood O(2) carrying capacity affects aerobic capacity (VO(2max)). Patients with type 1 diabetes have a risk for anaemia along with renal impairment, and they often have low VO(2max). We investigated whether total haemoglobin mass (tHb-mass) and blood volume (BV) differ in men with type 1 diabetes (T1D, n = 12) presently without complications and in healthy men (CON, n = 23) (age-, anthropometry-, physical activity-matched), to seek an explanation for low VO(2max). We determined tHb-mass, BV, haemoglobin concentration ([Hb]), and VO(2max) in T1D and CON. With similar (mean ± SD) [Hb] (144 vs. 145 g l(-1)), T1D had lower tHb-mass (10.1 ± 1.4 vs. 11.0 ± 1.1 g kg(-1), P < 0.05), BV (76.8 ± 9.5 vs. 83.5 ± 8.3 ml kg(-1), P < 0.05) and VO(2max) (35.4 ± 4.8 vs. 44.9 ± 7.5 ml kg(-1) min(-1), P < 0.001) than CON. VO(2max) correlated with tHb-mass and BV both in T1D (r = 0.71, P < 0.01 and 0.67, P < 0.05, respectively) and CON (r = 0.54, P < 0.01 and 0.66, P < 0.001, respectively), but not with [Hb]. Linear regression slopes were shallower in T1D than CON both between VO(2max) and tHb-mass (2.4 and 3.6 ml kg(-1) min(-1) vs. g kg(-1), respectively) and VO(2max) and BV (0.3 and 0.6 ml kg(-1) min(-1) vs. g kg(-1), respectively), indicating that T1D were unable to reach similar VO(2max) than CON at a given tHb-mass and BV. In conclusion, low tHb-mass and BV partly explained low VO(2max) in T1D and may provide early and more sensitive markers of blood O(2) carrying capacity than [Hb] alone.
[Show abstract][Hide abstract] ABSTRACT: AIMS: Electromagnetic interference (EMI) can pose a danger to workers with pacemakers and implantable cardioverter-defibrillators (ICDs). At some workplaces electromagnetic fields are high enough to potentially inflict EMI. The purpose of this in vivo study was to evaluate the susceptibility of pacemakers and ICDs to external electromagnetic fields.METHODS AND RESULTS: Eleven volunteers with a pacemaker and 13 with an ICD were exposed to sine, pulse, ramp, and square waveform magnetic fields with frequencies of 2-200 Hz using Helmholtz coil. The magnetic field flux densities varied to 300 µT. We also tested the occurrence of EMI from an electronic article surveillance (EAS) gate, an induction cooktop, and a metal inert gas (MIG) welding machine. All pacemakers were tested with bipolar settings and three of them also with unipolar sensing configurations. None of the bipolar pacemakers or ICDs tested experienced interference in any of the exposure situations. The three pacemakers with unipolar settings were affected by the highest fields of the Helmholtz coil, and one of them also by the EAS gate and the welding cable. The induction cooktop did not interfere with any of the unipolarly programmed pacemakers.CONCLUSION: Magnetic fields with intensities as high as those used in this study are rare even in industrial working environments. In most cases, employees can return to work after implantation of a bipolar pacemaker or an ICD, after an appropriate risk assessment. Pacemakers programmed to unipolar configurations can cause danger to their users in environments with high electromagnetic fields, and should be avoided, if possible.
[Show abstract][Hide abstract] ABSTRACT: Background. Asthma often begins in childhood or early adulthood and is a common disease among conscripts. The identification of long-term predictive factors for persistent asthma may lead to improved treatment opportunities and better disease control. Objective. Our aim was to study the prognostic factors of the severity of asthma among 40-year-old male conscripts whose asthma began in youth. Methods. We studied 119 conscripts who were referred to the Central Military Hospital during 1987-1990 due to asthma and who attended a follow-up visit approximately 20 years later. Asthma severity was evaluated during military service according to the medical records, and 20 years later during a follow-up visit using Global Initiative for Asthma guidelines. We used the results of lung function and allergy tests at baseline as predictors of current persistent asthma. Results. Compared with baseline, asthma was less severe at follow-up: 11.8% of subjects were in remission, 42.0% had intermittent asthma, 10.9% had mild persistent asthma, and 35.3% had moderate/severe persistent asthma (p < .001). In multivariate models, a positive exercise test at baseline yielded an odds ratio (OR) of 3.2 (95% CI 1.0-9.8, p = .046), a decreased FEV(1)/FVC % predicted an OR of 4.0 (95% CI 1.7-9.3, p = .002), and a decreased FEF(50%) % predicted an OR of 2.8 (95% CI 1.3-6.4, p = .012) for current persistent asthma. Conclusions. About half of the men had persistent asthma at the 20-year follow-up. Positive exercise tests and obstructive spirometry results were related to the persistence of asthma and may be useful long-term prognostic factors for asthma severity.
[Show abstract][Hide abstract] ABSTRACT: : To describe changes in aging firefighters' aerobic capacity at 3- and 13-year follow-ups, and to investigate the lifestyle factors predicting them. We evaluated the sufficiency of aerobic capacity for the demands of rescue diving.
: We studied 78 male Finnish firefighters aged 30 to 44 years at baseline. The outcome variable was aerobic capacity (L·min and mL·kg·min). The predictors were exercise, smoking, and drinking habits.
: The average annual change (range) in absolute and relative aerobic capacity was -1.12% (-3.43 to 1.39) and -1.33% (-3.98 to 1.63). Exercising at least 4 to 5 times a week was the best protective factor, and regular smoking and more than 15 units of alcohol a week were risk factors for decline in aerobic capacity.
: To prevent the excessive decline of aerobic capacity related to work demands, we must pay particular attention to exercise regularity.
Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine 08/2012; 54(9):1133-41. · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract Objectives. The aim of this study was to find the electromagnetic interference (EMI) thresholds for several commonly used implantable cardioverter-defibrillators (ICD). Design. Seventeen ICDs were exposed to magnetic fields with different intensities produced by the Helmholtz coil system. Sinusoidal, pulse, ramp, and square-waveforms with a frequency range of 2 Hz to 1 kHz were used. Results. ICD malfunctions occurred in 11 of the 17 ICDs tested. The ICD malfunctions that occurred were false detections of ventricular tachycardia (6/17 ICDs) and ventricular fibrillation (3/17 ICDs), false detection of atrial tachycardia (4/6 dual chamber ICDs) and tachycardia sensing occurring during atrial or ventricular refractory periods (1/17 ICD). In most cases, no interference occurred at magnetic field levels below the occupational safety limits of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Nevertheless, some frequencies using sine, ramp or square waveforms did interfere with certain ICDs at levels below these limits. No EMI occurred with any of the ICDs below the ICNIRP limits for public exposure. Conclusion. Evaluation of EMI should be part of the risk assessment of an employee returning to work after an ICD implantation. The risk assessment should consider magnetic field intensities, frequencies and waveforms.
[Show abstract][Hide abstract] ABSTRACT: The aim of the study was to evaluate the heat stress of Finnish male soldiers (N = 20, age 22.0 ± 2.5 years, body mass 78.8 ± 11.5 kg, and height 180.2 ± 5.6 cm) during their 4-month deployment in a hot environment and to find out the effects on physical performance and body composition. The troops moved from 2.5° C (mean monthly temperature) in Finland to 31.9° C in Chad. During the deployment, temperatures varied between 13.5 and 57.0° C outdoors and in the vehicles and tents. During 1-day recording in the middle of the deployment, skin temperatures were 34-35° C during daytime and maximal core temperature remained mainly below 38.0° C. Body mass decreased (78.4 ± 11.5 kg vs. 75.6 ± 8.6, p = 0.007) during the deployment without changes in fat mass. The sit-up performance increased by 10.9% (46 ± 10 reps·min⁻¹ vs. 51 ± 7 reps·min⁻¹, p < 0.01), and the maximal force production of the leg extensor muscles increased (3,042 ± 614 N vs. 3,277 ± 706 N, p < 0.05) without change in the rate of force development. No changes were observed in the push-ups, repeated squats, maximal grip strength, and running distance during the 12-minute test. In conclusion, the soldiers were able to maintain or improve their physical performance during the deployment despite the heat stress. It is important to encourage soldiers to engage in physical training, especially during a thermally appropriate time of the day or in air-conditioned facilities. Monitoring of local heat stress is also recommended.
The Journal of Strength and Conditioning Research 05/2012; 26 Suppl 2:S45-52. · 1.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Media work is characterized by information flow, deadlines, and 24/7 alertness. Good recovery prevents stress-related disorders.
The standardized questionnaire included items about health, health habits, sleep, work conditions, and work stress. Recordings of 24-hr heart rate variability (HRV) and four salivary samples for cortisol and melatonin levels were analyzed from 70 randomly selected workers with irregular shift work, and 70 workers with normal daytime work.
Irregular shift work increased the risk of insufficient recovery when compared to normal daytime work (OR 2.0; P < 0.05). In the group of workers with insufficient subjective recovery, HRV was attenuated (P < 0.05) during the early hours of night, and cortisol/melatonin ratio was decreased (P < 0.05) in the afternoon.
Physiological changes underlying subjective feelings of insufficient recovery are measurable. Attenuated HRV during sleep reflects prolonged sympathetic drive and/or impaired parasympathetic recovery. Interactions between cortisol and melatonin hormones might be involved in the development of chronic exhaustion.
American Journal of Industrial Medicine 04/2012; 55(7):643-9. · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An implantable cardioverter-defibrillator (ICD) experienced electromagnetic interference from a laptop computer's hard disk. The patient with the ICD was using his laptop computer at home while lying on his bed. The laptop was positioned on his chest, when he heard a beeping sound from the ICD, indicating magnet mode conversion. This situation was replicated in a controlled environment, and the conversion was found to be due to the static magnetic field produced by the laptop's hard disk. The ICD's conversion to magnet mode can be dangerous because it ends all tachyarrhythmia detections and therapies.
Pacing and Clinical Electrophysiology 02/2012; 35(6):e177-8. · 1.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to investigate whether the preschool activities challenge the stress regulative system in children. We used a multi-system approach to evaluate the underlying processes of stress responses and measured both cortisol and α-amylase responses after emotionally and cognitively challenging tasks followed by a recovery session. We anticipated that challenging tasks would increase both cortisol and α-amylase levels above the baseline. We further expected that recovery sessions would decrease both levels towards the baseline. In addition, we expected the symmetry of α-amylase and cortisol reactivity to be related to the ability to orientate towards cognitive demands. The study involved a total of 91 children (42 girls, 49 boys; six-year-olds). Baseline saliva samples were collected during a single day in October 2008. Reactivity saliva samples were collected during one morning in February 2009. During that day, the children first watched a movie with an experimenter who was unfamiliar to the children. After the movie, the children went to another room where the experimenter conducted all the cognitive tasks. These tasks were followed by a recovery session. The baseline cortisol levels indicated an average established function of the HPA (hypothalamic–pituitary–adrenocortical) system in the study children. Contrary to our hypothesis, only 19% of the study children showed the expected pattern of stress reactivity for both cortisol and α-amylase, with an average increase in cortisol and α-amylase levels following the challenging tasks. Unexpectedly, cortisol and α-amylase levels increased significantly in the singing recovery session. The surprising finding that singing seemed to be the only stimulating activity during the entire experimental situation raises questions about preschool practices.
Early Child Development and Care 02/2012; 182(2):175-189.
[Show abstract][Hide abstract] ABSTRACT: Cardiac pacemaker malfunction due to exposure to magnetic fields may cause serious problems in some work environments for workers having cardiac pacemakers. The aim of this study was to find the magnetic field interference thresholds for several commonly used pacemaker models.
We investigated 16 pacemakers from three different manufacturers with the frequency range of 2 to 1,000 Hz, using sinusoidal, pulse, ramp, and square waveforms. The magnetic fields were produced by a computer-controlled Helmholtz coil system.
Pacemaker malfunction occurred in six of 16 pacemakers. Interaction developed almost immediately after high-intensity magnetic field exposure started. With each waveform, at least two pacemakers exhibited interference. In most exposure settings, there was no interference at magnetic field levels below the international occupational safety limits. Nevertheless, some frequencies using ramp or square waveforms interfered with pacemakers even at levels below public exposure limits. The occurrence of interference depended greatly on the waveform, frequency, magnetic field intensity, and the sensing configuration of the pacemaker. Unipolar configurations were more susceptible for interference than the bipolar ones. In addition, magnetic fields perpendicular to the pacemaker loops were more likely to cause interference than parallel fields.
There is a need for further investigations on pacemaker interference caused by different external magnetic fields to ensure safe working environment to workers with a pacemaker.