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ABSTRACT: BACKGROUND: Obstructive sleep apnea (OSA) predisposes individuals to cardiovascular morbidity, and cardiopulmonary exercise test (CPET) markers prognostic for cardiovascular disease have been found to be abnormal in adults with OSA. Due to the persistence of OSA and its cardiovascular consequences, whether the cardiovascular adaptations normally conferred by exercise are blunted in adults not utilizing established OSA treatment is unknown. The aims of this study were to document whether OSA participants have abnormal CPET responses and determine whether exercise modifies these CPET markers in individuals with OSA. METHODS: The CPET responses of 43 sedentary, overweight adults (body mass index [BMI]>25) with untreated OSA (apnea-hypopnea index [AHI]≥15) were compared against matched non-OSA controls (n=9). OSA participants were then randomized to a 12-week exercise training (n=27) or stretching control treatment (n=16), followed by a post-intervention CPET. Measures of resting, exercise, and post-exercise recovery heart rate (HRR), blood pressure, and ventilation, as well as peak oxygen consumption (VO(2peak)), were obtained. RESULTS: OSA participants had blunted HRR compared to non-OSA controls at 1 (P=.03), 3 (P=.02), and 5-min post-exercise (P=.03). For OSA participants, exercise training improved VO(2peak) (P=.04) and HRR at 1 (P=.03), 3 (P<.01), and 5-min post-exercise (P<.001) compared to control. AHI change was associated with change in HRR at 5-min post-exercise (r=-.30, P<.05), but no other CPET markers. CONCLUSIONS: These results suggest that individuals with OSA have autonomic dysfunction, and that exercise training, by increasing HRR and VO(2peak), may attenuate autonomic imbalance and improve functional capacity independent of OSA severity reduction.
International journal of cardiology 05/2012; · 7.08 Impact Factor
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Stephen J Reynolds,
Maggie L Clark,
Niels Koehncke,
Susanna von Essen,
Linda Prinz,
Thomas J Keefe,
John Mehaffy,
Mary Bradford,
Brian Cranmer,
Margaret E Davidson,
Ivana V Yang, James B Burch
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ABSTRACT: Organic dust inhalation has been associated with adverse respiratory responses among agricultural workers. We evaluated factors that may confer increased susceptibility to these health effects.
We quantified personal work shift exposures to inhalable dust, endotoxin, and its 3-hydroxy fatty acid constituents, and evaluated changes in pulmonary function among 137 grain elevator, cattle feedlot, dairy, and corn farm workers.
Increased dust exposure was associated with work shift reductions in lung function. Although interpretation is limited because of small samples, a suggestion of stronger exposure-response relationships was observed among smokers, as well as workers reporting pesticide/herbicide application, asthma, or allergies, and those with genetic polymorphisms (TLR4) (Pinteraction ≤ 0.05).
A better understanding of factors leading to increased susceptibility of adverse respiratory outcomes is needed to optimize exposure reduction strategies and develop more comprehensive wellness programs.
Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine 05/2012; 54(5):632-41. · 1.88 Impact Factor
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ABSTRACT: To explore the utility of exercise training for improving daytime functioning in adults with obstructive sleep apnea (OSA).
Forty-three sedentary and overweight/obese adults aged 18-55 years with at least moderate-severity untreated OSA (apnea-hypopnea index ≥ 15) were randomized to 12 weeks of moderate-intensity aerobic and resistance exercise training (n = 27) or low-intensity stretching control treatment (n = 16). As part of a trial investigating the efficacy of exercise training on OSA severity, daytime functioning was assessed before and following the intervention. Sleepiness, functional impairment due to sleepiness, depressive symptoms, mood, and quality of life (QOL) were evaluated with validated questionnaires, and cognitive function was assessed with a neurobehavioral performance battery. OSA severity was measured with one night of laboratory polysomnography before and following the intervention.
Compared with stretching control, exercise training resulted in significant improvements in depressive symptoms, fatigue and vigor, and aspects of QOL (p < 0.05). Sleepiness and functional impairment due to sleepiness also were improved following exercise versus control to a similar degree in terms of effect sizes (d > 0.5), though these changes were not statistically significant. No neurobehavioral performance improvements were found. Reduced fatigue following exercise training was mediated by a reduction in OSA severity, but changes in OSA severity did not significantly mediate improvement in any other measure of daytime functioning.
These data provide preliminary evidence that exercise training may be helpful for improving aspects of daytime functioning of adults with OSA. Larger trials are needed to further verify the observed improvements.
Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 01/2012; 8(4):357-65. · 3.23 Impact Factor
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ABSTRACT: When performed competently, colonoscopy screening can reduce colorectal cancer rates, especially in high-risk groups such as African Americans. Training primary care physicians (PCPs) to perform colonoscopy may improve screening rates among underserved high-risk populations.
The authors compared colonoscopy screening rates and computed adjusted odds ratios for colonoscopy-eligible patients of trained African American PCPs (study group) versus untrained PCPs (comparison group), before and after initiating colonoscopy training. All colonoscopies were performed at a licensed ambulatory surgery center with specialist standby support. Retrospective chart review was conducted on 200 consecutive, established outpatients aged ≥50 years at each of 12 PCP offices (7 trained African American PCPs and 5 untrained PCPs, practicing in the same geographic region). There were a total of 1244 study group and 923 comparison group patients.
Post-training colonoscopy rates in both groups were higher than pretraining rates: 48.3% versus 9.3% in the study group, 29.6% versus 9.8% in the comparison group (both P < .001). African American patients in the study group showed a >5-fold increase (8.9% pretraining vs 52.8% post-training), with no change among whites (18.2% vs 25.0%). Corresponding pretraining and post-training rates among comparison patients were 10.4%% and 38.7%, respectively, among African Americans (P < .001), and 13.3% versus 13.2%, respectively, among whites. After adjusting for demographics, duration since becoming the PCP's patient, and health insurance, the study group had a 66% higher likelihood of colonoscopy in the post-training period (odds ratio, 1.66; 95% confidence interval, 1.30-2.13), and African Americans had a 5-fold increased likelihood of colonoscopy relative to whites.
Colonoscopy-trained PCPs may help reduce colorectal cancer disparities.
Cancer 04/2011; 117(22):5151-60. · 4.77 Impact Factor
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ABSTRACT: To evaluate the efficacy of a 12-week exercise training program for reducing obstructive sleep apnea (OSA) severity and improving sleep quality, and to explore possible mechanisms by which exercise may reduce OSA severity.
Randomized controlled trial.
Clinical exercise physiology center, sleep laboratory.
Forty-three sedentary and overweight/obese adults aged 18-55 years with at least moderate-severity untreated OSA (screening apnea-hypopnea index [AHI] ≥ 15).
Participants randomized to exercise training (n = 27) met 4 times/week for 12 weeks and performed 150 min/week of moderate-intensity aerobic activity, followed by resistance training twice/week. Participants randomized to a stretching control (n = 16) met twice weekly for 12 weeks to perform low-intensity exercises designed to increase whole-body flexibility.
OSA severity was assessed with one night of laboratory polysomnography (PSG) before and following the 12-week intervention. Measures of sleep quality included PSG, actigraphy (7-10 days), and the Pittsburgh Sleep Quality Index. Compared with stretching, exercise resulted in a significant AHI reduction (exercise: 32.2 ± 5.6 to 24.6 ± 4.4, stretching: 24.4 ± 5.6 to 28.9 ± 6.4; P < 0.01) as well as significant changes in oxygen desaturation index (ODI; P = 0.03) and stage N3 sleep (P = 0.03). Reductions in AHI and ODI were achieved without a significant decrease in body weight. Improvements in actigraphic sleep and subjective sleep quality were also noted following exercise compared with stretching.
Exercise training had moderate treatment efficacy for the reduction of AHI in sedentary overweight/obese adults, which suggests that exercise may be beneficial for the management of OSA beyond simply facilitating weight loss.
Clinicaltrials.gov identification number NCT00956423.
Sleep 01/2011; 34(12):1631-40. · 5.05 Impact Factor
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ABSTRACT: This ecologic study tested the hypothesis that census tracts with elevated groundwater uranium and more frequent groundwater use have increased cancer incidence.
Data sources included: incident total, leukemia, prostate, breast, colorectal, lung, kidney, and bladder cancers (1996-2005, SC Central Cancer Registry); demographic and groundwater use (1990 US Census); and groundwater uranium concentrations (n = 4,600, from existing federal and state databases). Kriging was used to predict average uranium concentrations within tracts. The relationship between uranium and standardized cancer incidence ratios was modeled among tracts with substantial groundwater use via linear or semiparametric regression, with and without stratification by the proportion of African Americans in each area.
A total of 134,685 cancer cases were evaluated. Tracts with ≥50% groundwater use and uranium concentrations in the upper quartile had increased risks for colorectal, breast, kidney, prostate, and total cancer compared to referent tracts. Some of these relationships were more likely to be observed among tracts populated primarily by African Americans.
SC regions with elevated groundwater uranium and more groundwater use may have an increased incidence of certain cancers, although additional research is needed since the design precluded adjustment for race or other predictive factors at the individual level.
Cancer Causes and Control 11/2010; 22(1):41-50. · 2.88 Impact Factor
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ABSTRACT: Environmental uranium exposure originating as a byproduct of uranium processing can impact human health. The Fernald Feed Materials Production Center functioned as a uranium processing facility from 1951 to 1989, and potential health effects among residents living near this plant were investigated via the Fernald Medical Monitoring Program (FMMP).
Data from 8216 adult FMMP participants were used to test the hypothesis that elevated uranium exposure was associated with indicators of hypertension or changes in hematologic parameters at entry into the program. A cumulative uranium exposure estimate, developed by FMMP investigators, was used to classify exposure. Systolic and diastolic blood pressure and physician diagnoses were used to assess hypertension; and red blood cells, platelets, and white blood cell differential counts were used to characterize hematology. The relationship between uranium exposure and hypertension or hematologic parameters was evaluated using generalized linear models and quantile regression for continuous outcomes, and logistic regression or ordinal logistic regression for categorical outcomes, after adjustment for potential confounding factors.
Of 8216 adult FMMP participants 4187 (51%) had low cumulative uranium exposure, 1273 (15%) had moderate exposure, and 2756 (34%) were in the high (>0.50 Sievert) cumulative lifetime uranium exposure category. Participants with elevated uranium exposure had decreased white blood cell and lymphocyte counts and increased eosinophil counts. Female participants with higher uranium exposures had elevated systolic blood pressure compared to women with lower exposures. However, no exposure-related changes were observed in diastolic blood pressure or hypertension diagnoses among female or male participants.
Results from this investigation suggest that residents in the vicinity of the Fernald plant with elevated exposure to uranium primarily via inhalation exhibited decreases in white blood cell counts, and small, though statistically significant, gender-specific alterations in systolic blood pressure at entry into the FMMP.
Environmental Research 10/2010; 110(8):786-97. · 3.40 Impact Factor
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James B Burch,
Erik Svendsen,
Paul D Siegel,
Sara E Wagner,
Susanna von Essen,
Thomas Keefe,
John Mehaffy,
Angelica Serrano Martinez,
Mary Bradford,
Laura Baker,
Brian Cranmer,
Rena Saito,
John Tessari,
Prinz Linda,
Colene Andersen,
Opal Christensen,
Niels Koehncke,
Stephen J Reynolds
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ABSTRACT: The adverse respiratory effects of agricultural dust inhalation are mediated in part by endotoxin, a constituent of gram-negative bacterial cell walls. This study quantified personal work-shift exposures to inhalable dust, endotoxin, and its reactive 3-hydroxy fatty acid (3-OHFA) constituents among workers in grain elevators, cattle feedlots, dairies, and on corn farms. Exposures were compared with post-work-shift nasal lavage fluid inflammation markers and respiratory symptoms. Breathing-zone personal air monitoring was performed over one work shift to quantify inhalable dust (Institute of Medicine samplers), endotoxin (recombinant factor C [rFC] assay), and 3-OHFA (gas chromatography/mass spectrometry). Post-shift nasal lavage fluids were assayed for polymorphonuclear neutrophils (PMN), myeloperoxidase (MPO), interleukin 8 (IL-8), albumin, and eosinophilic cation protein (ECP) concentrations. The geometric mean (GSD) of endotoxin exposure (rFC assay) among the 125 male participants was 888 +/- (6.5) EU/m(3), and 93% exceeded the proposed exposure limit (50 EU/m(3)). Mean PMN, MPO, albumin, and ECP levels were two- to threefold higher among workers in the upper quartile of 3-OHFA exposure compared to the lowest exposure quartile. Even numbered 3-OHFA were most strongly associated with nasal inflammation. Symptom prevalence was not elevated among exposed workers, possibly due to endotoxin tolerance or a healthy worker effect in this population. This is the first study to evaluate the relationship between endotoxin's 3-OHFA constituents in agricultural dust and nasal airway inflammation. More research is needed to characterize the extent to which these agents contribute to respiratory disease among agricultural workers.
Journal of Toxicology and Environmental Health Part A 01/2010; 73(1):5-22. · 1.83 Impact Factor
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Jaclyn Guess, James B Burch,
Kisito Ogoussan,
Cheryl A Armstead,
Hongmei Zhang,
Sara Wagner,
James R Hebert,
Patricia Wood,
Shawn D Youngstedt,
Lorne J Hofseth,
Udai P Singh,
Dawen Xie,
William J M Hrushesky
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ABSTRACT: Circadian disruption has been linked with inflammation, an established cancer risk factor. Per3 clock gene polymorphisms have also been associated with circadian disruption and with increased cancer risk. Patients completed a questionnaire and provided a blood sample prior to undergoing a colonoscopy (n = 70). Adjusted mean serum cytokine concentrations (IL-6, TNF-alpha, gamma-INF, IL-1ra, IL-1-beta, VEGF) were compared among patients with high and low scores for fatigue (Multidimensional Fatigue Inventory), depressive symptoms (Beck Depression Inventory II), or sleep disruption (Pittsburgh Sleep Quality Index), or among patients with different Per3 clock gene variants. Poor sleep was associated with elevated VEGF, and fatigue-related reduced activity was associated with elevated TNF-alpha concentrations. Participants with the 4/5 or 5/5 Per3 variable tandem repeat sequence had elevated IL-6 concentrations compared to those with the 4/4 genotype. Biological processes linking circadian disruption with cancer remain to be elucidated. Increased inflammatory cytokine secretion may play a role.
Integrative Cancer Therapies 11/2009; 8(4):329-36. · 2.14 Impact Factor
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ABSTRACT: Comparisons of incidence and mortality rates are the metrics used most commonly to define cancer-related racial disparities. In the US, and particularly in South Carolina, these largely disfavor African Americans (AAs). Computed from readily available data sources, the mortality-to-incidence rate ratio (MIR) provides a population-based indicator of survival.
South Carolina Central Cancer Registry incidence data and Vital Registry death data were used to construct MIRs. ArcGIS 9.2 mapping software was used to map cancer MIRs by sex and race for 8 Health Regions within South Carolina for all cancers combined and for breast, cervical, colorectal, lung, oral, and prostate cancers.
Racial differences in cancer MIRs were observed for both sexes for all cancers combined and for most individual sites. The largest racial differences were observed for female breast, prostate, and oral cancers, and AAs had MIRs nearly twice those of European Americans (EAs).
Comparing and mapping race- and sex-specific cancer MIRs provides a powerful way to observe the scope of the cancer problem. By using these methods, in the current study, AAs had much higher cancer MIRs compared with EAs for most cancer sites in nearly all regions of South Carolina. Future work must be directed at explaining and addressing the underlying differences in cancer outcomes by region and race. MIR mapping allows for pinpointing areas where future research has the greatest likelihood of identifying the causes of large, persistent, cancer-related disparities. Other regions with access to high-quality data may find it useful to compare MIRs and conduct MIR mapping.
Cancer 04/2009; 115(11):2539-52. · 4.77 Impact Factor
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ABSTRACT: Shiftwork among health care workers impacts upon the safety and health of both employees and patients.
To characterize shiftwork-related attitudes, behaviours, symptoms and coping strategies among health care workers, two validated questionnaires (the Standard Shiftwork Index and the Pressure Management Indicator) were used to identify factors predicting shiftwork adaptation.
Participants (n = 376, response rate 25%) were grouped according to their work schedule (days, permanent evenings, rotating days plus evenings, permanent nights or relief and combined shifts). Indicators of lifestyle, work organization, sleep disruption, health and pressure management among workers on irregular shifts were compared with participants on day shifts, after adjustment for gender, age and marital status. Principal components analysis and ordinal logistic regression were used among irregular shiftworkers to identify factors predicting schedule adaptation.
Night and relief/combined shiftworkers reported a greater ability to accommodate irregular schedules and disrupted sleep, but were also more likely to report work-related impacts than day workers. Permanent night workers generally reported poorer health, more absenteeism and less job satisfaction than day workers. Factors associated with optimal work performance or schedule contentment among shiftworkers included adequate sleep, evening circadian preference, increased age and organizational satisfaction. Reduced work performance or schedule discontent was associated with sleep/wake difficulties and poor health.
This study confirmed previous research and identified factors that can be targeted for the development of more effective shiftwork adaptation programmes in a health care setting (sleep timing and duration, exercise and optimal health and organizational satisfaction).
Occupational Medicine 04/2009; 59(3):159-66. · 1.14 Impact Factor
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Jovelyn Du-Quiton,
Patricia A Wood, James B Burch,
James F Grutsch,
Digant Gupta,
Kevin Tyer,
Christopher G Lis,
Robert D Levin,
Dinah Faith T Quiton,
Justin L Reynolds,
William J M Hrushesky
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ABSTRACT: We measured subjectively evaluated depression and anxiety, and objectively measured daily sleep-activity patterns in inpatients and outpatients with advanced non-small cell lung cancer (NSCLC) and determined whether cancer-associated depression and anxiety are accompanied by characteristic circadian rhythm abnormalities.
Equal numbers of inpatients (n=42) and outpatients (n=42) with advanced NSCLC were studied. Baseline depression and anxiety, assessed by the Hospital Anxiety and Depression Scale (HADS), and actigraphy were recorded before chemotherapy initiation. The effects of the presence and severity of chronic obstructive pulmonary disease (COPD) on depression, anxiety, and actigraphy were assessed only among the 42 outpatients.
Anxiety occurred in 40% and depression in 25% of these lung cancer patients, equally among inpatients and outpatients. All patients suffer extremely disturbed daily sleep-activity cycles but each patient also maintains some degree of circadian organization. Outpatients maintain more robust daily activity patterns and longer, more consolidated nighttime sleep compared with inpatients. The more disrupted the daily sleep-activity rhythm, the worse the depression and/or anxiety scores for outpatients. These relationships are obscured among inpatients. COPD has no independent measurable effects on the daily organization of sleep-activity, depression, or anxiety.
Lung cancer patients whose diurnal activity is disturbed by prolonged and frequent sedentary episodes and whose sleep is disturbed by frequent and prolonged waking are most anxious and depressed. These findings and relationships are masked by hospitalization. Since diurnal exercise improves both sleep and mood, it is reasonable to test whether enhancing daytime activity and nighttime sleep can diminish cancer-associated depression.
Psycho-Oncology 02/2009; 19(2):180-9. · 3.34 Impact Factor
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ABSTRACT: Elevated geomagnetic activity has been linked with human psychological, neurological and cardiovascular outcomes, and altered melatonin production has been implicated as an underlying mechanism to explain these effects. The relationship between geomagnetic activity and overnight excretion of the melatonin metabolite, 6-hydroxymelatonin sulfate (6-OHMS), was evaluated in a population of 153 male electric utility workers. The effect of geomagnetic activity combined with either 60Hz magnetic field or ambient light exposures was also evaluated. Elevated equivalent amplitudes (USGS, Boulder, CO) were associated with lower adjusted mean nocturnal 6-OHMS/cr concentrations and reduced total overnight 6-OHMS excretion, consistent with a previous study. Time intervals in which geomagnetic activity predicted the largest differences in mean 6-OHMS excretion generally occurred between 15- and 33-h prior to urine sample collection. These times coincide with key periods of melatonin regulation and production, respectively, suggesting that geomagnetic activity may play a role in the entrainment of human melatonin rhythms.
Neuroscience Letters 07/2008; 438(1):76-9. · 2.11 Impact Factor
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ABSTRACT: The sleep-time responses to ethanol, pentobarbital, and methyprylon were assessed in various generations derived from crossing the long-sleep (LS) and short-sleep (SS) mouse lines in order to assess whether common or different genes regulate response to these agents. The LS and SS mice were selectively bred for differences in duration of ethanol-induced sleep time. Ethanol and pentobarbital responses segregate in a different fashion into F1 and F2 generations derived from the LS and SS lines, indicating different genie control and probably different mechanisms of action for these two agents. Ethanol and methyprylon response segregated similarly but fewer genes seem to influence methyprylon response. These results support the notion that water-soluble depressants have common mechanisms of action.
Alcoholism Clinical and Experimental Research 01/2008; 8(6):546 - 550. · 3.34 Impact Factor
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ABSTRACT: Metabolites of estrogen (estrone-3-glucuronide [E1G]) and melatonin (6-hydroxymelatonin sulfate [6-OHMS]) were characterized among women living in a community with increased radiofrequency (RF) exposure from radio and television transmitters.
RF spot measurements, and personal 60-Hz magnetic field and residential parameters were collected. Overnight urine samples were assayed for E1G and 6-OHMS excretion.
Among premenopausal women, there were no associations between RF or 60-Hz nonionizing radiation and E1G or 6-OHMS excretion. Among postmenopausal women, increased residential RF exposures, transmitter proximity and visibility, and temporally stable 60-Hz exposures were significantly associated with increased E1G excretion. This association was strongest among postmenopausal women with low overnight 6-OHMS levels.
RF and temporally stable 60-Hz exposures were associated with increased E1G excretion among postmenopausal women. Women with reduced nocturnal 6-OHMS excretion may represent a sensitive subgroup.
Journal of Occupational and Environmental Medicine 11/2007; 49(10):1149-56. · 2.06 Impact Factor
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ABSTRACT: Increased breast cancer risks have been reported among women with gross cystic breast disease (GCBD), although the mechanism for this increase remains unexplained. Relationships between GCBD characteristics, breast cancer risk factors, and the biochemical composition and growth properties of 142 breast cyst fluid (BCF) samples were studied among 93 women with GCBD. Concentrations of melatonin, estrogen (17-beta-estradiol), dehydroepiandrosterone-sulfate (DHEA-S), epidermal growth factor (EGF), transforming growth factor beta (TGF-B1 and TGF-B2), sodium (Na), and potassium (K) were quantified in BCF samples, and human breast cancer cells (MCF-7) were treated with BCF in vitro. Patients were grouped according to BCF Na:K ratios previously linked with increased breast cancer risks (Na:K </= 3, Type 1), and mean concentrations of BCF constituents were compared with low risk (Na:K > 3, Type 2) and mixed cyst groups. Women with larger and more frequently occurring cysts had higher BCF estrogen and DHEA-S, and lower TGF-B1 levels. Women with Type 1 cysts had elevated BCF melatonin, estrogen, DHEA-S, and EGF, and lower concentrations of TGF-B2 compared to women with Type 2 cysts. BCF generally inhibited cell growth relative to serum-treated controls, consistent with previous studies. Melatonin and estrogen in BCF independently predicted growth inhibition and stimulation, respectively. Biological monitoring of BCF may help identify women with GCBD at greatest risk for breast cancer development.
Breast Cancer Research and Treatment 07/2007; 103(3):331-41. · 4.43 Impact Factor
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Journal of the South Carolina Medical Association (1975) 09/2006; 102(7):212-20.
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ABSTRACT: Exposure to radio frequency (RF) nonionizing radiation from telecommunications is pervasive in modern society. Elevated disease risks have been observed in some populations exposed to radio and television transmissions, although findings are inconsistent. This study quantified RF exposures among 280 residents living near the broadcasting transmitters for Denver, Colorado. RF power densities outside and inside each residence were obtained, and a global positioning system (GPS) identified geographic coordinates and elevations. A view-shed model within a geographic information system (GIS) characterized the average distance and percentage of transmitters visible from each residence. Data were collected at the beginning and end of a 2.5-day period, and some measurements were repeated 8-29 months later. RF levels logged at 1-min intervals for 2.5 days varied considerably among some homes and were quite similar among others. The greatest differences appeared among homes within 1 km of the transmitters. Overall, there were no differences in mean residential RF levels compared over 2.5 days. However, after a 1- to 2-year follow-up, only 25% of exterior and 38% of interior RF measurements were unchanged. Increasing proximity, elevation, and line-of-sight visibility were each associated with elevated RF exposures. At average distances from > 1-3 km, exterior RF measurements were 13-30 times greater among homes that had > 50% of the transmitters visible compared with homes with < or = 50% visibility at those distances. This study demonstrated that both spatial and temporal factors contribute to residential RF exposure and that GPS/GIS technologies can improve RF exposure assessment and reduce exposure misclassification.
Environmental Health Perspectives 02/2006; 114(2):248-53. · 7.04 Impact Factor
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ABSTRACT: Night work is associated with disrupted circadian rhythms, fatigue, accidents, and chronic disease. Melatonin secretion helps regulate sleep and circadian rhythms.
Melatonin, sleep disturbances, and symptoms (sleep, fatigue, mental) were compared among workers on permanent day, swing, and night shifts.
Urinary 6-hydroxymelatonin sulfate (6-OHMS) was measured in postwork and postsleep samples. Disrupted circadian melatonin production was evaluated using the sleep:work 6-OHMS ratio. Wrist actigraphy characterized light exposures and sleep characteristics.
Night workers had altered melatonin, disrupted sleep, and elevated symptom prevalence. Subjects grouped by their sleep:work 6-OHMS ratio rather than shift had even greater symptom prevalence. Risks for two or more symptoms were 3.5 to 8 times greater among workers with sleep:work ratios < or =1 compared to those with ratios >1.
This ratio may help identify workers at increased risk for accidents or injuries.
Journal of Occupational and Environmental Medicine 10/2005; 47(9):893-901. · 2.06 Impact Factor
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ABSTRACT: The effects of a 60-Hz magnetic field (MF) exposure on white blood cell ornithine decarboxylase (ODC) activity, natural killer (NK) cell activity, lymphocyte phenotypes, and differential cell counts were studied among 60 electric utility workers. Personal MF exposure monitoring over 3 consecutive workdays was followed by collection of a peripheral blood sample. There were no MF-related changes in NK activity or the number of circulating neutrophils, eosinophils, basophils, or T-lymphocytes (CD4, CD8, CD4:CD8 ratio). MF exposure intensity was associated with decreased ODC activity (P<0.01) and lower NK cell counts (P=0.04). Melatonin production, which stimulates the immune system, was quantified on the night preceding immune marker determinations. Exposure-related reductions in ODC activity, NK and B cells, and monocytes were strongest among workers with reduced melatonin production. The biological significance or long-term health consequences associated with these changes are not known.
Journal of Occupational and Environmental Medicine 03/2004; 46(2):104-12. · 2.06 Impact Factor
