We examined the association of night shift work history and age when night shift work was performed with cancer and cardiovascular disease risk factors among 54 724 women in the Nurses' Health Study (NHS) II.
We calculated age-adjusted and socioeconomic status-adjusted means and percentages for cancer and cardiovascular risk factors in 2009 across categories of night shift work history. We used multivariable-adjusted logistic regression to estimate odds ratios (ORs) and 95% CIs for key risk factors among 54 724 participants (72% ever shift workers). We further examined these associations by age (20–25, 26–35, 36– 45 and 46+ years) at which shift work was performed.
Ever night shift workers had increased odds of obesity (body mass index ≥30 kg/m2; OR=1.37, 95% CI 1.31 to 1.43); higher caffeine intake (≥131 mg/day; OR=1.16, 95% CI 1.12 to 1.22) and total calorie intake (≥1715 kcal/day; OR=1.09, 95% CI 1.04 to 1.13); current smoking (OR=1.30, 95% CI 1.19 to 1.42); and shorter sleep durations (≤7 h of sleep/day; OR=1.19, 95% CI 1.15 to 1.24) compared to never night shift workers. These estimates varied depending on age at which night work was performed, with a suggestion that night shift work before age 25 was associated with fewer risk factors compared to night shift work at older ages.
Our results indicate that night shift work may contribute to an adverse chronic disease risk profile, and that risk factors may vary depending on the age at which night shift work was performed.
To assess the effects of long-term variations in ambient air pollutants on longitudinal changes in exhaled nitric oxide (FeNO), a potentially useful biomarker of eosinophilic airway inflammation, based on data from the southern California Children’s Health Study.
Based on a cohort of 1,211 schoolchildren from 8 Southern California communities with FeNO measurements in 2006/07 and 2007/08, regression models adjusted for short-term effects of air pollution were fitted to assess the association between changes in annual long-term exposures and changes in FeNO.
Increases in annual average concentrations of 24-hr average NO2 and PM2.5 (scaled to the interquartile range (IQR) of 1.8 ppb and 2.4 μg/m3, respectively) were associated with a 2.29 ppb (CI=[0.36,4.21]; p =0.02) and a 4.94 ppb (CI=[1.44,8.47]; p = 0.005) increase in FeNO, respectively, after adjustments for short term effects of the respective pollutants. In contrast, changes in annual averages of PM10 and O3 were not significantly associated with changes in FeNO. These findings did not differ significantly by asthma status.
Changes in annual average exposure to current levels of ambient air pollutants are significantly associated with changes in FeNO levels in children, independent of short-term exposures and asthma status. Use of this biomarker in population-based epidemiologic research has great potential for assessing the impact of changing real world mixtures of ambient air pollutants on children’s respiratory health.
Air pollution; chronic exposures; Children’s respiratory health; Environmental epidemiology; Exhaled nitric oxide; Airway inflammation
Between 2001 and 2010, five research groups conducted coordinated prospective studies of carpal tunnel syndrome (CTS) incidence among US workers from various industries and collected detailed subject-level exposure information with follow-up of symptoms, electrophysiological measures and job changes.
This analysis examined the associations between workplace biomechanical factors and incidence of dominant-hand CTS, adjusting for personal risk factors.
2474 participants, without CTS or possible polyneuropathy at enrolment, were followed up to 6.5 years (5102 person-years). Individual workplace exposure measures of the dominant hand were collected for each task and included force, repetition, duty cycle and posture. Task exposures were combined across the workweek using time-weighted averaging to estimate job-level exposures. CTS case-criteria were based on symptoms and results of electrophysiological testing. HRs were estimated using Cox proportional hazard models.
After adjustment for covariates, analyst (HR=2.17; 95% CI 1.38 to 3.43) and worker (HR=2.08; 95% CI 1.31 to 3.39) estimated peak hand force, forceful repetition rate (HR=1.84; 95% CI 1.19 to 2.86) and per cent time spent (eg, duty cycle) in forceful hand exertions (HR=2.05; 95% CI 1.34 to 3.15) were associated with increased risk of incident CTS. Associations were not observed between total hand repetition rate, per cent duration of all hand exertions, or wrist posture and incident CTS.
In this prospective multicentre study of production and service workers, measures of exposure to forceful hand exertion were associated with incident CTS after controlling for important covariates. These findings may influence the design of workplace safety programmes for preventing work-related CTS.
Agricultural pesticide handlers are at an elevated risk for overexposure to
organophosphate (OP) pesticides, but symptoms can be difficult to recognize, making
biomarkers invaluable for diagnosis. Occupational monitoring programs for cholinesterase
depression generally rely on measuring activity of either of two common blood
cholinesterases which serve as proxy measurements for nervous-system
acetylcholinesterase activity: red blood cell acetylcholinesterase (AChE) and plasma
butyrylcholinesterase (BChE). These biomarkers, however, may be affected differentially
by some OPs and the relationship between them has not been well characterized. We aim to
determine the association between blood acetylcholinesterase (AChE) and
butyrylcholinesterase (BChE) activity levels and assess whether they produce comparable
classifications of clinical cholinesterase depression among organophosphate pesticide
Using blood samples from 215 participants of the Washington State
Cholinesterase Monitoring Program, we quantified changes in AChE and BChE activity from
before and after exposure to OP pesticides and calculated Pearson correlation statistics
for correlation of AChE and BChE changes in activity, as well as weighted Kappa
statistics for agreement of classification of clinical cholinesterase depression based
on AChE versus BChE measurements.
AChE and BChE activity measurements are weakly negatively correlated in our
study population. Reaching a clinical threshold for diagnosis of cholinesterase
depression based on the AChE marker did not correlate with reaching clinical depression
based on the BChE marker.
Both AChE and BChE should be measured in monitoring programs because they may
both give potentially important but disparate classifications of clinical cholinesterase
cholinesterase inhibitors; organophosphate toxicity; acetylcholinesterase; butyrylcholinesterase
Asbestos describes a group of naturally occurring silicate mineral fibers that were widely used in industry during the 20th century due to their desirable physical properties. Although use in the United States has fallen over the last three decades, significant exposure in the developing world continues and the burden of disease is considerable. Asbestos is a known risk factor for several malignant diseases, including lung cancer and mesothelioma, and has more recently been implicated in pharyngeal and laryngeal cancer. However, studies of asbestos and cancers of the larynx or pharynx with adequate sample-size that control for major head and neck squamous cell carcinoma (HNSCC) risk factors remain relatively sparse.
We report findings from a case-control study of 674 incident male HNSCC cases from the greater Boston region and 857 population-based male controls, matched on age (+/− 3 years), sex, and town or neighborhood of residence. Multivariable logistic regression was used to assess the association between occupational asbestos exposure and HNSCC by primary tumor site.
A total of 190 cases (28.2%) and 203 controls (23.7%) reported an occupational exposure to asbestos. Occupational asbestos exposure was associated with an elevated risk of pharyngeal carcinoma in men (OR = 1.41, 95% CI: 1.01–1.97), adjusted for age, race, smoking, alcohol consumption, education, income, and HPV16 serology, with borderline increasing risk for each decade at the exposed occupation (OR = 1.10, 95% CI: 0.99–1.23).
These observations are consistent with the mounting evidence that asbestos is a risk factor for pharyngeal cancer.
HNSCC; head and neck cancer; epidemiology; RERI
Mental illness and psychotropic drugs have been linked with workplace injury, but few studies have measured exposures and outcomes independently or established their relative timings. To address this shortcoming, we conducted a case-control study nested within a database prospectively recording injury consultations, diagnoses and drug prescriptions.
The Clinical Practice Research Datalink logs primary care data for 6% of the British population, coding all consultations (by the Read system) and drug prescriptions. We identified 1,348 patients aged 16-64 years from this database who had consulted a family doctor or hospital over a 20-year period for workplace injury (cases, 479 diagnostic codes) and 6,652 age, sex, and practice-matched controls with no such consultation. Groups were compared in terms of consultations for mental health problems (1,328 codes) and prescription of psychotropic drugs prior to the case’s injury consultation, using conditional logistic regression.
In total, 1,846 (23%) subjects had at least one psychiatric consultation before the index date and 1,682 (21%) had been prescribed a psychotropic drug. The odds ratio for prior mental health consultation was 1.44 (P<0.001) and that for psychotropic drug treatment was 1.57 (P<0.001). Risks were significantly elevated for several subclasses of mental health diagnosis (e.g. psychosis, neurosis) and for each of the drug classes analysed. Assuming causal relationships, about 9-10% of all workplace injuries leading to medical consultation were attributable to mental illness or psychotropic medication.
Mental health problems and psychotropic treatments may account for an important minority of workplace injuries.
People in sedentary occupations are at increased risk of hip fracture. Hip fracture is significantly associated with low bone mineral density (BMD) measured at the hip. Physical activity is important in the development and maintenance of BMD but the effects of occupational physical activity on bone health are unclear. We investigated the influence of lifetime physical activity on bone mineral density at the hip.
This was a cross-sectional epidemiological study of the associations between total hip BMD measured by dual-energy X-ray absorptiometry at retirement age and lifetime exposure to occupational physical workload (standing/walking ≥4 hours/day; lifting ≥25 kg; energetic work sufficient to induce sweating and manual work).
Complete data on occupational exposures were available for 860 adults (488 men and 372 women) who had worked ≥ 20 years. Their mean age was 65 years and many reported heavy physical workplace activities over prolonged durations. There were no statistically significant associations between total hip BMD and any of these measures of lifetime occupational physical activity in men or women.
Lifetime cumulative occupational activity was not associated with hip bone mineral density at retirement age. Our findings suggest that, if sedentary work conveys an increased risk of hip fracture, it is unlikely that the mechanism is through reductions in bone mineral density at the hip and may relate to other physical effects, such as falls risk. Further studies will be needed to test this hypothesis.
Hip fractures; osteoporosis; bone mineral density; occupational physical activity
The relation between Dupuytren’s contracture and occupational exposure to hand-transmitted vibration (HTV) has frequently been debated. We explored associations in a representative national sample of workers with well-characterised exposure to HTV.
We mailed a questionnaire to 21,201 subjects aged 16 – 64 years, selected at random from the age-sex registers of 34 general practices in Great Britain and to 993 subjects chosen randomly from military pay records, asking about occupational exposure to 39 sources of HTV and about fixed flexion contracture of the little or ring finger. Analysis was restricted to men at work in the previous week. Estimates were made of average daily vibration dose (A(8) r.m.s.) over that week. Associations with Dupuytren’s contracture were estimated by Poisson regression, both for lifetime exposure to HTV and for exposures in the past week >A(8) of 2.8 ms−2 r.m.s.. Estimates of relative risk (Prevalence Ratio (PR)) were adjusted for age, smoking status, social class and certain manual activities at work.
In all 4,969 eligible male respondents supplied full information on the study variables. These included 72 men with Dupuytren’s contracture, 2,287 with occupational exposure to HTV, and 409 with A(8)>2.8 ms−2 in the past week. PRs for occupational exposure to HTV were elevated 1.5-fold. For men with an A(8)>2.8 ms−2 in the past week, the adjusted PR was 2.85 (95% confidence interval 1.37 to 5.97).
Our findings suggest that risk of Dupuytren’s contracture is more than doubled in men with high levels of weekly exposure to HTV.
There is limited information on the public health impact of wildfires. The relationship of cardiorespiratory hospital admissions (n = 40 856) to wildfire-related particulate matter (PM2.5) during catastrophic wildfires in southern California in October 2003 was evaluated.
Zip code level PM2.5 concentrations were estimated using spatial interpolations from measured PM2.5, light extinction, meteorological conditions, and smoke information from MODIS satellite images at 250 m resolution. Generalised estimating equations for Poisson data were used to assess the relationship between daily admissions and PM2.5, adjusted for weather, fungal spores (associated with asthma), weekend, zip code-level population and sociodemographics.
Associations of 2-day average PM2.5 with respiratory admissions were stronger during than before or after the fires. Average increases of 70 μg/m3 PM2.5 during heavy smoke conditions compared with PM2.5 in the pre-wildfire period were associated with 34% increases in asthma admissions. The strongest wildfire-related PM2.5 associations were for people ages 65– 99 years (10.1% increase per 10 μg/m3 PM2.5, 95% CI 3.0% to 17.8%) and ages 0–4 years (8.3%, 95% CI 2.2% to 14.9%) followed by ages 20–64 years (4.1%, 95% CI 20.5% to 9.0%). There were no PM2.5–asthma associations in children ages 5–18 years, although their admission rates significantly increased after the fires. Per 10 μg/m3 wildfire-related PM2.5, acute bronchitis admissions across all ages increased by 9.6% (95% CI 1.8% to 17.9%), chronic obstructive pulmonary disease admissions for ages 20–64 years by 6.9% (95% CI 0.9% to 13.1%), and pneumonia admissions for ages 5–18 years by 6.4% (95% CI 21.0% to 14.2%). Acute bronchitis and pneumonia admissions also increased after the fires. There was limited evidence of a small impact of wildfire-related PM2.5 on cardiovascular admissions.
Wildfire-related PM2.5 led to increased respiratory hospital admissions, especially asthma, suggesting that better preventive measures are required to reduce morbidity among vulnerable populations.
Although previous studies have related occupational exposure and epicondylitis, the evidence is moderate, and mostly based on cross-sectional studies. Suspected physical exposures were tested over a three year period in a large longitudinal cohort study of workers in the United States.
In a population-based study including a variety of industries, 1107 newly employed workers were examined; only workers without elbow symptoms at baseline were included. Baseline questionnaires collected information on personal characteristics and self-reported physical work exposures and psychosocial measures for the current or most recent job at 6 months. Epicondylitis (lateral and medial) was the main outcome, assessed at 36 months based on symptoms and physical examination (palpation or provocation test). Logistic models included the most relevant associated variables.
Of 699 workers tested after 36 months who did not have elbow symptoms at baseline, 48 suffered from medial or lateral epicondylitis (6.9%), with 34 cases of lateral epicondylitis (4.9%), 30 cases of medial epicondylitis (4.3%), and 16 workers who had both. After adjusting for age, lack of social support, and obesity, consistent associations were observed between self-reported wrist bending/twisting and forearm twisting/rotating/screwing motion and future cases of medial or lateral epicondylitis (odds ratios 2.8 [1.2;6.2] and 3.6 [1.2;11.0] respectively in men and women).
Self-reported physical exposures that implicate repetitive and extensive/prolonged wrist bend/twisting and forearm movements were associated with incident cases of lateral and medial epicondylitis in a large longitudinal study, although other studies are needed to better specify the exposures involved.
epicondylitis; observational study; occupational; risk factor; epidemiology
Evidence from general population based studies and occupational cohorts has identified air pollution from mobile sources as a risk factor for cardiovascular disease. In a cohort of US trucking industry workers, with regular exposure to vehicle exhaust, we previously observed elevated standardized mortality ratios (SMRs) for ischemic heart disease compared to members of the general US population. Therefore, we examined the association of increasing years of work in jobs with vehicle exhaust exposure and ischemic heart disease mortality within the cohort.
We calculated years of work in eight job groups for 30,758 workers using work records from four nationwide companies. Proportional hazard regression was used to examine relationships between ischemic heart disease mortality 1985–2000 and employment duration in each job group.
Hazard ratios for at least one year of work in each job were elevated for dockworkers, long-haul drivers, pick-up and delivery drivers, combination workers, hostlers, and shop workers. There was a suggestion of an increased risk of IHD mortality with increasing years of work as a long-haul driver, pick-up and delivery driver, combination worker, and dockworker.
These results suggest an elevated risk of ischemic heart disease mortality in workers with a previous history of regular exposure to vehicle exhaust.
vehicle emissions; diesel exhaust; cardiovascular disease
Metalworking has been associated with an excess risk of bladder cancer in over 20 studies. Metalworking fluids (MWFs) are suspected as the responsible exposure, but epidemiologic data are limited. We investigated this association among men in the New England Bladder Cancer Study using state-of-the-art, quantitative exposure assessment methods.
Cases (n=895) and population controls (n=1,031) provided occupational histories during personal interviews. For selected jobs, exposure-oriented modules were administered to collect information on use of three MWF types: (1) straight (mineral oil, additives), (2) soluble (mineral oil, water, additives), and (3) synthetic (water, organics, additives) or semi-synthetic (hybrid of soluble and synthetic). We computed odds ratios (ORs) and 95% confidence intervals (CIs) relating bladder cancer risk to a variety of exposure metrics, adjusting for smoking and other factors. Non-metalworkers who had held jobs with possible exposure to mineral oil were analyzed separately.
Bladder cancer risk was elevated among men who reported using straight MWFs (OR=1.7, 95% CI=1.1–2.8); risk increased monotonically with increasing cumulative exposure (p=0.041). Use of soluble MWFs was associated with a 50% increased risk (95% CI=0.96–2.5). ORs were nonsignificantly elevated for synthetic/semi-synthetic MWFs based on a small number of exposed men. Non-metalworkers holding jobs with possible exposure to mineral oil had a 40% increased risk (95% CI=1.1–1.8).
Exposure to straight MWFs was associated with a significantly increased bladder cancer risk, as was employment in non-metalworking jobs with possible exposure to mineral oil. These findings strengthen prior evidence for mineral oil as a bladder carcinogen.
Long working hours may be associated with cardiovascular disease (CVD). The objective was to investigate cross-sectional associations of work hours with carotid intima media thickness (CIMT) and ankle brachial index (ABI).
Participants were 1,694 women and 1,868 men from the Multi-Ethnic Study of Atherosclerosis. CIMT and ABI were measured using standard protocols. Information on work hours was obtained from questionnaires. Mean values of CIMT and ABI were examined across five categories of hours worked per week (≤20, 21-39, 40, 41-50, >50) using ANOVA/ANCOVA. P-values for trend were obtained from linear regression models.
Mean age of participants was 56.9±8.4 years; 52.4% were men. Distinct patterns of association between work hours and the subclinical CVD biomarkers were found for women and men, although this heterogeneity by gender was not statistically significant. Among women only, work hours were positively associated with common (but not internal) CIMT (p=0.073) after full risk factor adjustment. Compared to women working 40 hours, those working >50 hours were more likely to have an ABI <1 (vs. 1-1.4) (OR=1.85, 95% CI=1.01-3.38). In men, work hours and ABI were inversely associated (p=0.046). There was some evidence that the association between work hours and ABI was modified by occupational category (interaction p=0.061). Among persons classified as Management/Professionals, longer work hours was associated with lower ABI (p=0.015). No significant associations were observed among other occupational groups.
Working longer hours may be associated with subclinical CVD. These associations should be investigated using longitudinal studies.
Atherosclerosis; carotid artery stenosis; ankle-brachial index; work
Whereas accumulating evidence indicates close associations between rhinitis and asthma, little is known about the relationships between occupational rhinitis (OR) and occupational asthma (OA). This study analyses the prevalence of OR associated with OA, globally and according to the various causal agents, and investigates the temporal relationships between these two conditions.
Data on incident cases of OA (2008–2010) were collected through the French national occupational disease surveillance and prevention network, using a standardized form including information on occupation, causal agents, presence of OR, and respective dates of occurrence of rhinitis and asthma.
Among the 596 reported OA cases with latency period, 555 could be attributed to identified agents: high molecular weight (HMW) agents (n=174); low molecular weight (LMW) agents (n=381). Overall, OR was associated with OA in 324 (58.4%) cases. The frequency of association was significantly higher for HMW agents than for LMW agents (72.2% vs 51.5%, p<0.001). OR occurred before OA significantly more frequently for HMW agents than for LMW agents (p<0.01).
These results show that OR is frequently associated with OA, especially when HMW agents are involved. They are consistent with the hypothesis that OR, in conjunction with OA, is more likely to be caused by sensitizers that cause disease via IgE-mediated mechanisms and suggest that symptoms of OR should be taken into account in the medical surveillance of workers exposed to HMW agents.
Adult; Air Pollutants, Occupational; adverse effects; chemistry; Asthma, Occupational; epidemiology; etiology; Female; France; epidemiology; Humans; Incidence; Male; Middle Aged; Molecular Weight; Occupational Diseases; epidemiology; etiology; Occupations; statistics & numerical data; Odds Ratio; Prevalence; Rhinitis; epidemiology; etiology; occupational asthma; occupational rhinitis; high molecular weight; low molecular weight
Current understanding of the dose-response relationship between occupational noise and hearing loss is based on cross-sectional studies prior to the widespread use hearing protection and with limited data regarding noise exposures below 85dBA. We report on the hearing loss experience of a unique cohort of industrial workers with daily monitoring of noise inside of hearing protection devices.
At an industrial facility, workers exhibiting accelerated hearing loss were enrolled in a mandatory program to monitor daily noise exposures inside of hearing protection. We compared these noise measurements (as time-weighted LAVG) to interval rates of high frequency hearing loss over a six year period using a mixed effects model, adjusting for potential confounders.
Workers’ high frequency hearing levels at study inception averaged more than 40 dB hearing threshold level (HTL). Most noise exposures were less than 85dBA (mean LAVG 76 dBA, interquartile range 74 to 80 dBA). We found no statistical relationship between LAvg and high frequency hearing loss (p = 0.53). Using a metric for monthly maximum noise exposure did not improve model fit.
At-ear noise exposures below 85dBA did not show an association with risk of high frequency hearing loss among workers with substantial past noise exposure and hearing loss at baseline. Therefore, effective noise control to below 85dBA may lead to significant reduction in occupational hearing loss risk in such individuals. Further research is needed on the dose response relationship of noise and hearing loss in individuals with normal hearing and little prior noise exposure.
Hearing loss; Noise induced; Dose response
Telomere length has been proposed as a biomarker of cell senescence, which is associated with a wide array of adverse health outcomes. While work is a major determinant of health, few studies have investigated the association of telomere length with various dimensions of occupation. Accelerated cellular aging could be a common pathway linking occupational exposure to several health outcomes.
Leukocyte telomere length was assessed using quantitative polymerase chain reaction (Q-PCR) in a community-based sample of 981 individuals (age: 45–84 years old). Questionnaires were used to collect information on current employment status, current or main occupation before retirement, and job strain. The O*NET (Occupational Resource Network) database was linked to the questionnaire data to create 5 exposure measures: physical activity on the job, physical hazard exposure, interpersonal stressors, job control, and job demands. Linear regression was used to estimate associations of occupational characteristics with telomere lengths after adjustment for age, sex, race, socioeconomic position, and several behavioral risk factors.
There were no mean differences in telomere lengths across current employment status, occupational category, job strain categories or levels of most O*NET exposure measures. There was also no evidence that being in lower status occupational categories or being exposed to higher levels of adverse physical or psychosocial exposures accelerated the association between age and telomere shortening.
Cellular aging as reflected by shorter telomeres does not appear to be an important pathway linking occupation to various health outcomes.
The risk factors for sporadic (i.e. non-familial) retinoblastoma remain largely unknown. However, some studies have suggested a role for paternal work activities, primarily in farming and the metalworking industry, in the development of childhood retinoblastoma.
We examined the relationship between paternal occupational exposures from jobs held 10 years and one year prior to conception and the risk of sporadic bilateral retinoblastoma in children.
Paternal occupational data were obtained for 198 incident cases diagnosed with sporadic bilateral retinoblastoma from January 1998 to May 2006 and 245 referral-based controls from the case child’s relatives and friends who were matched to 135 of the cases on birth year. Industrial hygienists independently assigned exposure scores for nine agents, including estimates of probability, intensity, and frequency as well as an overall summary exposure score. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression models, using the full sample of cases and controls as well as subset of cases with matched controls only.
There was some indication of an elevated risk associated with paternal pesticide exposure in the 10 years prior to conception (OR= 1.64; 95% CI: 1.08-2.50) as well as in the year before conception (OR= 2.12; 95% CI: 1.25-3.61). However, results for pesticide exposure were inconsistent and varied by analysis approach. An increased risk was also observed for non-welding metal exposure during the 10 years prior to conception in the full (OR= 1.35; 95% CI: 0.86-2.12) and matched (OR= 1.40; 95% CI: 0.82-2.37) samples, but not in the year before conception. Exposure-response trends were observed for pesticides in the full sample (p for trend < 0.0001), and consistently across both samples for non-welding metal exposures.
Our findings suggest a potential role of paternal occupational exposures to non-welding metals and perhaps pesticides in the etiology of childhood retinoblastoma.
germline mutation; retinoblastoma; child; occupational exposure; case-control studies
Evaluating occupational exposures in population-based case-control studies often requires exposure assessors to review each study participants' reported occupational information job-by-job to derive exposure estimates. Although such assessments likely have underlying decision rules, they usually lack transparency, are time-consuming and have uncertain reliability and validity. We aimed to identify the underlying rules to enable documentation, review, and future use of these expert-based exposure decisions.
Classification and regression trees (CART, predictions from a single tree) and random forests (predictions from many trees) were used to identify the underlying rules from the questionnaire responses and an expert's exposure assignments for occupational diesel exhaust exposure for several metrics: binary exposure probability and ordinal exposure probability, intensity, and frequency. Data were split into training (n=10,488 jobs), testing (n=2,247), and validation (n=2,248) data sets.
The CART and random forest models' predictions agreed with 92–94% of the expert's binary probability assignments. For ordinal probability, intensity, and frequency metrics, the two models extracted decision rules more successfully for unexposed and highly exposed jobs (86–90% and 57–85%, respectively) than for low or medium exposed jobs (7–71%).
CART and random forest models extracted decision rules and accurately predicted an expert's exposure decisions for the majority of jobs and identified questionnaire response patterns that would require further expert review if the rules were applied to other jobs in the same or different study. This approach makes the exposure assessment process in case-control studies more transparent and creates a mechanism to efficiently replicate exposure decisions in future studies.
diesel exhaust; classification; data mining; occupational exposure
Animal evidence suggests that circadian disruption may be associated with ovarian cancer, though very little epidemiologic work has been done to assess this potential association. We evaluated the association between self-reported nightshift work, a known circadian disruptor, and ovarian cancer in a population-based case-control study.
The study included 1,101 women with invasive epithelial ovarian cancer, 389 women with borderline epithelial ovarian tumors and 1,832 controls and was conducted in Western Washington State. Shift work data was collected as part of in-person interviews.
Working the nightshift was associated with an increased risk of invasive (OR=1.24, 95% CI: 1.04–1.49) and borderline (OR=1.48, 95% CI: 1.15–1.90) tumors; however, we observed little evidence that risks increased with increasing cumulative duration of nightshift work, and risks were not elevated in the highest duration category (>7 nightshift work-years). Increased risks were restricted to women who were 50 years of age and older and to serous and mucinous histologies of invasive and borderline tumors. There was suggestive evidence of a decreased risk of ovarian cancer among women reporting a preference for activity during evenings rather than mornings.
We found evidence suggesting an association between shift work and ovarian cancer. This observation should be followed up in future studies incorporating detailed assessments of diurnal preference (i.e. chronotype) in addition to detailed data on shift schedules.
shift work; ovarian cancer; circadian; chronotype
Chronic low level exposure of agricultural workers and applicators to pesticides has been found to be associated with different degrees of decrement in cognitive and psychomotor functions. The goal of this study was to use meta-analysis to (1) identify and quantify neurobehavioral deficits among agricultural workers and pesticide applicators, and (2) analyse the potential confounders or moderators of these neurobehavioral deficits. Seventeen studies, reporting on 21 independent cohort groups, were included in the meta-analysis. These studies involved 16 neuropsychological tests providing 23 different performance measures that constitute the neurobehavioral constructs. All tests and measures of the neurobehavioral functions of attention, visuomotor integration, verbal abstraction and perception constructs showed significant decrements for exposed participants. One out of three tests of memory, two of five tests of sustained attention, and four of eight tests of motor speed constructs also showed significant decrements. Nine out of these 15 effect size distributions demonstrated significant heterogeneity across cohorts. A search for cohort-level variables (eg, agricultural workers vs applicators, duration of exposure, age and percentage of male participants) to explain this heterogeneity was largely unsuccessful. However, for one test, Block Design, the duration of exposure was positively associated with performance decrements. Furthermore, it was also found that performance decrements on this test were smaller for older participants. Increasing the number of studies and using more consistent methodologies in field studies are needed.
Recent investigations have associated airborne Particulate Matter (PM) with increased coagulation and thrombosis, but underlying biological mechanisms are still incompletely characterized. DNA methylation is an environmentally-sensitive mechanism of gene regulation that could potentially contribute to PM-induced hypercoagulability. We aimed to test whether altered methylation mediates environmental effects on coagulation.
We investigated 63 steel workers exposed to a wide range of PM levels, as a work-related condition with well-characterized prothrombotic exposure. We measured personal PM10 (PM≤10 μm in aerodynamic diameter), PM1 (≤1 μm), and air metal components. We determined leukocyte DNA methylation of NOS3 (nitric-oxide-synthase-3) and EDN1 (endothelin-1) through bisulfite-pyrosequencing and we measured Endogenous Thrombin Potential (ETP), as a global coagulation-activation test after standardized triggers.
ETP increased in association with PM10 (β=20.0, 95%CI: 3.0, 37.0), PM1 (β=80.8 95%CI: 14.9, 146.7), and zinc (β=51.3, 95%CI: 0.01, 111.1) exposures. NOS3 methylation was negatively associated with PM10 (β=−0.2, 95%CI: −0.4, −0.03), PM1 (β=−0.8, 95%CI: −1.4, −0.1), zinc (β=−0.9, 95%CI: −1.4, −0.3) and iron (β=−0.7, 95%CI: −1.4, −0.01) exposures. Zinc exposure was negatively associated with EDN1 (β=−0.3, 95%CI: −0.8, −0.1) methylation. Lower NOS3 (β=−42.3; p<0.001) and EDN1 (β=−14.5; p=0.05) were associated with higher ETP. Statistical mediation analysis formally confirmed NOS3 and EDN1 hypomethylation as intermediate mechanisms for PM-related coagulation effects.
Our study showed for the first time, that gene hypomethylation contributes to environmentally-induced hypercoagulability.
Air pollution; DNA methylation; coagulation
To quantify the variation in rates of absence for musculoskeletal pain across 47 occupational groups (mostly nurses and office workers) from 18 countries, and to explore personal and group-level risk factors that might explain observed differences.
A standardised questionnaire was used to obtain information about musculoskeletal pain, sickness absence and possible risk factors in a cross-sectional survey of 12,416 workers (92 to 1017 per occupational group). In addition, group-level data on socioeconomic variables such as sick pay and unemployment rates were assembled by members of the study team in each country. Associations of sickness absence with risk factors were examined by Poisson regression.
Overall, there were more than 30-fold differences between occupational groups in the 12-month prevalence of prolonged musculoskeletal sickness absence, and even among office workers carrying out similar occupational tasks, the variation was more than ten-fold. Personal risk factors included older age, lower educational level, tendency to somatise, physical loading at work and prolonged absence for non-musculoskeletal illness. However, these explained little of the variation between occupational groups. After adjustment for individual characteristics, prolonged musculoskeletal sickness absence was more frequent in groups with greater time pressure at work, lower job control, and more adverse beliefs about the work-relatedness of musculoskeletal disorders.
Musculoskeletal sickness absence might be reduced by eliminating excessive time pressures in work, maximising employees’ responsibility and control, and providing flexibility of duties for those with disabling symptoms. Care should be taken not to overstate work as a cause of musculoskeletal injury.
Sickness absence; musculoskeletal; international; risk factors; time pressure; job control
Chlorinated solvents are classified as probable or possible carcinogens. It is unknown whether exposure to these agents increases the risk of malignant or benign brain tumors. Our objective was to evaluate associations of brain tumor risk with occupational exposure to six chlorinated solvents [i.e., dichloromethane, chloroform, carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, and perchloroethylene].
489 glioma cases, 197 meningioma cases, and 799 controls were enrolled in a hospital-based case-control study conducted at three U.S. hospitals in Arizona, Massachusetts and Pennsylvania. Information about occupational history was obtained through a detailed in-person interview that included job-specific modules of questions such that the interview was tailored to each individual’s particular work history. An industrial hygienist assessed potential solvent exposure based on this information and an exhaustive review of the relevant industrial hygiene literature. Unconditional logistic regression models were used to calculate odds ratios (OR) and 95% confidence intervals (95%CI) for each solvent for ever/never, duration, cumulative, average weekly, and highest exposure.
Overall, we found no consistent evidence of an increased risk of glioma or meningioma related to occupational exposure to the six chlorinated solvents evaluated. There was some suggestion of an association between carbon tetrachloride and glioma in analyses restricted to exposed subjects, with average weekly exposure above the median associated with increased risk compared to below-median exposure (OR=7.1, 95%CI: 1.1, 45.2).
We found no consistent evidence for increased brain tumor risk related to chlorinated solvents.
epidemiology; cancer; solvents