Respective Mediating Effects of Social Position and Work Environment on the Incidence of Common Cardiovascular Risk Factors.

Background Social position and work environment are highly interrelated and their respective contribution to cardiovascular risk is still debated. Methods and Results In a cohort of 20 625 French workers followed for 25 years, discrete-time survival analysis with reciprocal mediating effects, adjusted for sex, age, and parental history of early coronary heart disease, was performed using Bayesian structural equation modeling to simultaneously investigate the extent to which social position mediates the effect of work environment and, inversely, the extent to which work environment mediates the effect of social position on the incidence of common cardiovascular risk factors. Depending on the factor, social position mediates 2% to 53% of the effect of work environment and work environment mediates 9% to 87% of the effect of social position. The mediation by work environment is larger than that by social position for the incidence of obesity, hypertension, dyslipidemia, diabetes, sleep complaints, and depression (mediation ratios 1.32-41.5, 6.67 when modeling the 6 factors together). In contrast, the mediation by social position is larger than that by work environment for the incidence of nonmoderate alcohol consumption, smoking, and leisure-time physical inactivity (mediation ratios 0.16-0.69, 0.26 when modeling the 3 factors together). Conclusions The incidence of behavioral risk factors seems strongly dependent on social position whereas that of clinical risk factors seems closely related to work environment, suggesting that preventive strategies should be based on education and general practice for the former and on work organization and occupational medicine for the latter.

Work environment mediates a large part of social inequalities in the incidence of several common cardiovascular risk factors: Findings from the Gazel cohort.

Whether working conditions contribute to social inequalities in cardiovascular disease is still a matter of debate. The present study investigates the extent to which the social gradient in the incidence of common behavioral and clinical risk factors is explained by work environment. In a well-characterized cohort of 20,625 middle-aged French civil servants followed for 25 years, social status and work environment were globally measured at baseline by combining respectively four socioeconomic indicators (education, wealth, income, occupational grade) and 25 physical, biomechanical, organizational and psychosocial occupational exposures. These 2 global measures are strongly correlated with each other (p < 0.0001), lower is social status, worse is work environment. In proportional hazard regression models adjusted for sex, age and parental cardiovascular disease, low social status increases the incidence of 9 risk factors with hazard ratios ranging from 1.12 to 1.72 while bad work environment increases the incidence of 7 risk factors with hazard ratios ranging from 1.15 to 2.02. Structural equation models to discrete-time survival analysis with moderated mediation show that bad work environment explains nearly 50% of the global effect of low social status on the incidence of the 9 risk factors (p < 0.01). This mediating effect varies substantially from one risk factor to another, explaining 32-39% of social gradients in the risk of physical inactivity, obesity, diabetes, dyslipidemia and 64-90% of gradients in the risk of hypertension, sleep complaints and depression (all p < 0.01). No significant mediating effect of work environment is found for social gradients in the incidence of non-moderate alcohol consumption and smoking. These results suggest that work environment mediates a large part of the social gradient in the incidence of several common cardiovascular risk factors, emphasizing the necessity to include working conditions in policies aimed to reduce social inequalities in health.

Primary Cardiovascular Disease Risk Factors Predicted by Poor Working Conditions in the GAZEL Cohort.

The mechanisms by which work environment might influence cardiovascular disease (CVD) risk are still a matter of debate. In particular, the involvement of the main behavioral and clinical risk factors and their relationships with working conditions are not always clear, despite an abundant body of literature. Most studies have investigated the impact of a limited number of characteristics of the work environment on the occurrence of 1 or a few risk factors. In contrast, in this study we used a global approach in which 30 objective and subjective indicators of working conditions were tested as predictors of 9 modifiable CVD risk factors in a well-characterized cohort of 20,625 middle-aged French workers who were followed from the 1990s until they retired or until December 31, 2013. The incidence of 3 CVD risk factors (obesity, sleep complaints, and depression) was predicted by a large number of indicators of working conditions in both age- and sex-adjusted and multivariate-adjusted Cox regression models, whatever the significance threshold retained. These results suggest the existence of close relationships between a poor work environment and a higher risk of developing obesity, sleep complaints, or depression. These risk factors may contribute to increased CVD risk not only when workers are exposed to poor working conditions but also after retirement, as predictors of the appearance of other risk factors.

A Global View of the Relationships between the Main Behavioural and Clinical Cardiovascular Risk Factors in the GAZEL Prospective Cohort.

Although it has been recognized for a long time that the predisposition to cardiovascular diseases (CVD) is determined by many risk factors and despite the common use of algorithms incorporating several of these factors to predict the overall risk, there has yet been no global description of the complex way in which CVD risk factors interact with each other. This is the aim of the present study which investigated all existing relationships between the main CVD risk factors in a well-characterized occupational cohort. Prospective associations between 12 behavioural and clinical risk factors (gender, age, parental history of CVD, non-moderate alcohol consumption, smoking, physical inactivity, obesity, hypertension, dyslipidemia, diabetes, sleep disorder, depression) were systematically tested using Cox regression in 10,736 middle-aged individuals free of CVD at baseline and followed over 20 years. In addition to independently predicting CVD risk (HRs from 1.18 to 1.97 in multivariable models), these factors form a vast network of associations where each factor predicts, and/or is predicted by, several other factors (n = 47 with p<0.05, n = 37 with p<0.01, n = 28 with p<0.001, n = 22 with p<0.0001). Both the number of factors associated with a given factor (1 to 9) and the strength of the associations (HRs from 1.10 to 6.12 in multivariable models) are very variable, suggesting that all the factors do not have the same influence within this network. These results show that there is a remarkably extensive network of relationships between the main CVD risk factors which may have not been sufficiently taken into account, notably in preventive strategies aiming to lower CVD risk.

Occupational biomechanical exposure predicts low back pain in older age among men in the Gazel Cohort.

PURPOSE: Occupational biomechanical exposures are considered as risk factors for low back pain in the working population. It has also been suggested that their effects persist after retirement. Our objectives were to assess the role of past biomechanical occupational exposure on low back pain in early old age among male participants of the Gazel Cohort. METHODS: Low back pain for more than 30 days in the past 12 months (LBP30) was assessed in 1996 and 2006 using a French version of the Nordic questionnaire in a subsample of the Gazel Cohort. Logistic regression models were used to study associations between LBP30 in 2006 and past occupational biomechanical exposure, self-reported in 1996, taking into account personal and psychosocial work factors self-reported in 1996, and the date of retirement provided by the company. A multinomial model served to study persistent and new cases, according to LBP30 in 1996. RESULTS: We studied 1,520 men aged 58-67 in 2006, most of them retired. Low back pain for more than 30 days in the past 12 months reported in 2006 was related to occupational biomechanical exposure encountered many years earlier (OR 1.55, 95% CI 1.05-2.27 for 10-20 years of exposure to bending/twisting, OR 1.71, 95% CI 1.17-2.49 for >20 years). These associations appeared specific to low back pain for more than 30 days in the past 12 months which persisted between 1996 and 2006. CONCLUSION: These results suggest that occupational biomechanical exposure during active life has persistent effects among men in early old age, even for people who left the workforce. They point out the importance of preventive measures at work for better health later and appear relevant for policy-making decisions concerning age at retirement.

Work stress and risk of cancer: meta-analysis of 5700 incident cancer events in 116,000 European men and women.

OBJECTIVE: To investigate whether work related stress, measured and defined as job strain, is associated with the overall risk of cancer and the risk of colorectal, lung, breast, or prostate cancers. DESIGN: Meta-analysis of pooled prospective individual participant data from 12 European cohort studies including 116,056 men and women aged 17-70 who were free from cancer at study baseline and were followed-up for a median of 12 years. Work stress was measured and defined as job strain, which was self reported at baseline. Incident cancers (all n=5765, colorectal cancer n=522, lung cancer n=374, breast cancer n=1010, prostate cancer n=865) were ascertained from cancer, hospital admission, and death registers. Data were analysed in each study with Cox regression and the study specific estimates pooled in meta-analyses. Models were adjusted for age, sex, socioeconomic position, body mass index (BMI), smoking, and alcohol intake RESULTS: A harmonised measure of work stress, high job strain, was not associated with overall risk of cancer (hazard ratio 0.97, 95% confidence interval 0.90 to 1.04) in the multivariable adjusted analyses. Similarly, no association was observed between job strain and the risk of colorectal (1.16, 0.90 to 1.48), lung (1.17, 0.88 to 1.54), breast (0.97, 0.82 to 1.14), or prostate (0.86, 0.68 to 1.09) cancers. There was no clear evidence for an association between the categories of job strain and the risk of cancer. CONCLUSIONS: These findings suggest that work related stress, measured and defined as job strain, at baseline is unlikely to be an important risk factor for colorectal, lung, breast, or prostate cancers.

Job strain as a risk factor for leisure-time physical inactivity: an individual-participant meta-analysis of up to 170,000 men and women: the IPD-Work Consortium.

Unfavorable work characteristics, such as low job control and too high or too low job demands, have been suggested to increase the likelihood of physical inactivity during leisure time, but this has not been verified in large-scale studies. The authors combined individual-level data from 14 European cohort studies (baseline years from 1985-1988 to 2006-2008) to examine the association between unfavorable work characteristics and leisure-time physical inactivity in a total of 170,162 employees (50% women; mean age, 43.5 years). Of these employees, 56,735 were reexamined after 2-9 years. In cross-sectional analyses, the odds for physical inactivity were 26% higher (odds ratio = 1.26, 95% confidence interval: 1.15, 1.38) for employees with high-strain jobs (low control/high demands) and 21% higher (odds ratio = 1.21, 95% confidence interval: 1.11, 1.31) for those with passive jobs (low control/low demands) compared with employees in low-strain jobs (high control/low demands). In prospective analyses restricted to physically active participants, the odds of becoming physically inactive during follow-up were 21% and 20% higher for those with high-strain (odds ratio = 1.21, 95% confidence interval: 1.11, 1.32) and passive (odds ratio = 1.20, 95% confidence interval: 1.11, 1.30) jobs at baseline. These data suggest that unfavorable work characteristics may have a spillover effect on leisure-time physical activity.

Job strain and tobacco smoking: an individual-participant data meta-analysis of 166,130 adults in 15 European studies.

BACKGROUND: Tobacco smoking is a major contributor to the public health burden and healthcare costs worldwide, but the determinants of smoking behaviours are poorly understood. We conducted a large individual-participant meta-analysis to examine the extent to which work-related stress, operationalised as job strain, is associated with tobacco smoking in working adults. METHODOLOGY AND PRINCIPAL FINDINGS: We analysed cross-sectional data from 15 European studies comprising 166,130 participants. Longitudinal data from six studies were used. Job strain and smoking were self-reported. Smoking was harmonised into three categories never, ex- and current. We modelled the cross-sectional associations using logistic regression and the results pooled in random effects meta-analyses. Mixed effects logistic regression was used to examine longitudinal associations. Of the 166,130 participants, 17% reported job strain, 42% were never smokers, 33% ex-smokers and 25% current smokers. In the analyses of the cross-sectional data, current smokers had higher odds of job strain than never-smokers (age, sex and socioeconomic position-adjusted odds ratio: 1.11, 95% confidence interval: 1.03, 1.18). Current smokers with job strain smoked, on average, three cigarettes per week more than current smokers without job strain. In the analyses of longitudinal data (1 to 9 years of follow-up), there was no clear evidence for longitudinal associations between job strain and taking up or quitting smoking. CONCLUSIONS: Our findings show that smokers are slightly more likely than non-smokers to report work-related stress. In addition, smokers who reported work stress smoked, on average, slightly more cigarettes than stress-free smokers.

Job strain and alcohol intake: a collaborative meta-analysis of individual-participant data from 140,000 men and women.

BACKGROUND: The relationship between work-related stress and alcohol intake is uncertain. In order to add to the thus far inconsistent evidence from relatively small studies, we conducted individual-participant meta-analyses of the association between work-related stress (operationalised as self-reported job strain) and alcohol intake. METHODOLOGY AND PRINCIPAL FINDINGS: We analysed cross-sectional data from 12 European studies (n = 142 140) and longitudinal data from four studies (n = 48 646). Job strain and alcohol intake were self-reported. Job strain was analysed as a binary variable (strain vs. no strain). Alcohol intake was harmonised into the following categories: none, moderate (women: 1-14, men: 1-21 drinks/week), intermediate (women: 15-20, men: 22-27 drinks/week) and heavy (women: >20, men: >27 drinks/week). Cross-sectional associations were modelled using logistic regression and the results pooled in random effects meta-analyses. Longitudinal associations were examined using mixed effects logistic and modified Poisson regression. Compared to moderate drinkers, non-drinkers and (random effects odds ratio (OR): 1.10, 95% CI: 1.05, 1.14) and heavy drinkers (OR: 1.12, 95% CI: 1.00, 1.26) had higher odds of job strain. Intermediate drinkers, on the other hand, had lower odds of job strain (OR: 0.92, 95% CI: 0.86, 0.99). We found no clear evidence for longitudinal associations between job strain and alcohol intake. CONCLUSIONS: Our findings suggest that compared to moderate drinkers, non-drinkers and heavy drinkers are more likely and intermediate drinkers less likely to report work-related stress.

Long-term effects of biomechanical exposure on severe shoulder pain in the Gazel cohort.

OBJECTIVE: We aimed to assess whether the risk factors for severe shoulder pain, especially exposure to arm elevation, were still relevant after a 12-year follow-up, even following retirement. METHODS: All men participating in the ARPEGE ancillary study of the GAZEL cohort (followed-up since 1989) and who answered the 1994 or 1995 general GAZEL self-administered questionnaire were included. Weight and self-reported exposure (arm elevation >90° with and without carrying loads) over the entire working life were collected at baseline (1994-1995). Shoulder pain and its intensity were recorded in 1994-1995 and again in 2006. Shoulder pain was measured on an intensity or discomfort 6-point scale in 1994-1995 and on an 8-point scale in 2006. Severe shoulder pain was defined as point-rated higher than the mid-points (>3/6 in 1994-1995 and >4/8 in 2006) while moderate pain was lower or equal to these thresholds. RESULTS: At baseline, 1786 47-51-year-old men were included. In 1994-1995, moderate pain was observed among 8.5% (N=151) of men and severe shoulder pain among 14.6% (N=261). Exposure to arm elevation >90° while carrying loads was significantly associated with severe shoulder pain with >25 years of exposure [adjusted odds ratio (OR (adj)) 4.2, 95% confidence interval (95% CI) 1.7-10.5], taking into account age, sports, smoking habits, history of shoulder trauma, and body mass index. In 2006, when most of the subjects had retired, 1482 men (83.0%) answered the questionnaire, 17.3% of them with severe shoulder pain; the association between exposure to arm elevation >90° while carrying loads and severe shoulder pain was still significant (ORadj 3.3, 95% CI 1.3-8.0), and remained so when subjects with shoulder pain at baseline were excluded. CONCLUSIONS: Among men, the effect of high shoulder exposure (arm elevation >90° while carrying loads) during working life on severe shoulder pain remains even after retirement. Extended surveillance and prevention should be offered to these workers.

Comparison of alternative versions of the job demand-control scales in 17 European cohort studies: the IPD-Work consortium.

BACKGROUND: Job strain (i.e., high job demands combined with low job control) is a frequently used indicator of harmful work stress, but studies have often used partial versions of the complete multi-item job demands and control scales. Understanding whether the different instruments assess the same underlying concepts has crucial implications for the interpretation of findings across studies, harmonisation of multi-cohort data for pooled analyses, and design of future studies. As part of the 'IPD-Work' (Individual-participant-data meta-analysis in working populations) consortium, we compared different versions of the demands and control scales available in 17 European cohort studies. METHODS: Six of the 17 studies had information on the complete scales and 11 on partial scales. Here, we analyse individual level data from 70 751 participants of the studies which had complete scales (5 demand items, 6 job control items). RESULTS: We found high Pearson correlation coefficients between complete scales of job demands and control relative to scales with at least three items (r > 0.90) and for partial scales with two items only (r = 0.76-0.88). In comparison with scores from the complete scales, the agreement between job strain definitions was very good when only one item was missing in either the demands or the control scale (kappa > 0.80); good for job strain assessed with three demand items and all six control items (kappa > 0.68) and moderate to good when items were missing from both scales (kappa = 0.54-0.76). The sensitivity was > 0.80 when only one item was missing from either scale, decreasing when several items were missing in one or both job strain subscales. CONCLUSIONS: Partial job demand and job control scales with at least half of the items of the complete scales, and job strain indices based on one complete and one partial scale, seemed to assess the same underlying concepts as the complete survey instruments.

Post-retirement surveillance of workers exposed to asbestos or wood dust: first results of the French national SPIRALE Program.

OBJECTIVES: In France, 15 000-20 000 cancers attributable to occupational exposure occur each year. These cancers appear most often after the worker has retired. Since 1995, a system of post-retirement medical surveillance (PRMS) has been set up for former workers, but it remains largely underused. DESIGN: The SPIRALE program is a public health intervention aimed at identifying the former workers having been exposed to asbestos or wood dust during their working life and to propose them a PRMS. Additionally, it is also an epidemiologic research on the longterm effects of occupational exposure.We report the results of first years of the program conducted in 2006-2008, in 13 districts. SETTING AND PARTICIPANTS: a self-administered questionnaire was sent to 50 000 newly retired men, to identify potential past occupational carcinogen exposure. For respondents detected as possibly exposed, exposure was assessed in Health Screening Centres and a PRMS was recommended if necessary. MAIN OUTCOME MEASURES: Participation rate, rate of confirmed exposure, increased rate of PRMS, satisfaction about the program. RESULTS: The participation rate was 24%. From 12 002 questionnaires analysed, 72% of respondents were identified as possibly exposed: 3%to wood dust, 50%to asbestos and 19%to both exposures. Exposure to asbestos was confirmed for 73.4%, and according to the level of exposure, PRMS was recommended for 47.1%. Wood dust exposure was confirmed for 56.7%. In these districts, PRMS for asbestos increased by 45% and for wood dust by 600%. Additional surveys showed that participants showed a high degree of satisfaction about the program. CONCLUSIONS: The results are positive in terms of detection, information and medical surveillance of exposed workers.

Impact of diabetes on work cessation: data from the GAZEL cohort study.

OBJECTIVE: To measure the impact of diabetes on work cessation, i.e., on the risks of work disability, early retirement, and death while in the labor force. RESEARCH DESIGN AND METHODS: We used data from the GAZEL prospective cohort of 20,625 employees of the French national gas and electricity company "EDF-GDF." We identified 506 employees with diabetes and randomly selected 2,530 nondiabetic employed control subjects matched for major sociodemographic and occupational characteristics. Using a multistate Cox model, we estimated hazard ratios (HRs) comparing the risks of transition from employment to disability, retirement, and death over time between participants with versus without diabetes. RESULTS: Employment rate decreased more rapidly in participants with diabetes (51.9 and 10.1% at 55 and 60 years, respectively) compared with nondiabetic participants (66.5 and 13.4%, respectively). Participants with diabetes had significantly increased risks of transition from employment to disability (HR 1.7 [95% CI 1.0-2.9]), retirement (HR 1.6 [1.5-1.8]), and death (HR 7.3 [3.6-14.6]) compared with participants without diabetes. Between 35 and 60 years, each participant with diabetes lost an estimated mean time of 1.1 year in the workforce (95% CI 0.99-1.14) compared with a nondiabetic participant. CONCLUSIONS: Our results provide evidence for a profound negative impact of diabetes on workforce participation in France. Social and economic consequences are major for patients, employers, and society-a burden that is likely to increase as diabetes becomes more and more common in the working-aged population.

Informal caregiving and self-reported mental and physical health: results from the Gazel Cohort Study.

OBJECTIVES: We investigated whether, and under what conditions, informal caregiving is associated with improved self-reported physical and mental health, most notably in terms of cognitive functioning. METHODS: We performed a cross-sectional analysis of 2008 data from the Gazel Cohort Study, which involved 10 687 men and women aged 54 to 70 years. Multivariate linear and logistic regression models were used to estimate the associations between self-reported health and caregiving status and burden. RESULTS: Regular caregivers with the highest burden scores reported significantly worse health status than did noncaregivers for almost all of the physical and mental outcomes evaluated after adjustment for potential confounding factors. In particular, they reported more cognitive complaints (odds ratio [OR] = 1.44; 95% confidence interval [CI] = 1.21, 1.73). Conversely, caregivers with the lowest burden scores reported better perceived health status, less physical and mental tiredness, and fewer depressive symptoms (OR = 0.50; 95% CI = 0.37, 0.68) than did noncaregivers; however, they did not report decreases in cognitive difficulties (OR = 0.98; 95% CI = 0.81, 1.18). CONCLUSIONS: Our findings support the hypothesis that caregiving can have positive effects on health, provided that caregiving activities themselves are not too heavy a burden.

Long-term effects of biomechanical exposure on severe knee pain in the Gazel cohort.

OBJECTIVE: Little is known about the long-term effect of occupational determinants on knee pain. We aimed to assess whether the risk factors for severe knee pain, observed with a cross-sectional approach, were still relevant after retirement, 12 years later. METHODS: All men participating in the ARPEGE side study of the GAZEL cohort (employees of the French national utility for energy production and distribution, recruited in 1989) and who answered the 1994 or 1995 general GAZEL self-administered questionnaire, were included. Weight and self-reported exposures over the entire working life were collected at baseline. Knee pain and its intensity were recorded in 1994-1995 and again in 2006. Moderate and severe knee pain, defined from an intensity or discomfort scale (threshold 3 on a 6-level scale in 1994-1995, and 4 on an 8-level scale in 2006), were the main outcomes. RESULTS: At baseline, 1786 men were included. In 1994-1995, moderate knee pain was observed among 10.3% and severe pain in 12.8% of men. In 2006, 1482 men (83%) answered the questionnaire. Moderate and severe knee pain were observed in 18.6% and 16.3% of respondents, respectively. Working in a kneeling or squatting position was significantly associated with severe knee pain at baseline, taking into account age, sports, smoking habits, and body mass index [adjusted odds ratio (OR (adj)) 1.4, 95% confidence interval (95% CI) 1.1-1.9 for "ever exposed" and OR (adj)2.0, 95% CI 1.3-3.1 for >25 years of exposure]. In 2006, when most subjects were retired, the association between working in a kneeling or squatting position and severe pain was weaker but still significant (OR (adj)1.4, 95% CI 1.04-1.85). CONCLUSIONS: The effect of high knee exposure in the working life on severe knee pain remains even after retirement, although decreased. An extended surveillance and prevention program for these workers could be proposed.

The CONSTANCES cohort: an open epidemiological laboratory.

BACKGROUND: Prospective cohorts represent an essential design for epidemiological studies and allow for the study of the combined effects of lifestyle, environment, genetic predisposition, and other risk factors on a large variety of disease endpoints. The CONSTANCES cohort is intended to provide public health information and to serve as an "open epidemiologic laboratory" accessible to the epidemiologic research community. Although designed as a "general-purpose" cohort with very broad coverage, it will particularly focus on occupational and social determinants of health, and on aging. METHODS: The CONSTANCES cohort is designed as a randomly selected representative sample of French adults aged 18-69 years at inception; 200,000 subjects will be included over a five-year period. At inclusion, the selected subjects will be invited to fill a questionnaire and to attend a Health Screening Center (HSC) for a comprehensive health examination: weight, height, blood pressure, electrocardiogram, vision, auditory, spirometry, and biological parameters; for those aged 45 years and older, a specific work-up of functional, physical, and cognitive capacities will be performed. A biobank will be set up. The follow-up includes a yearly self-administered questionnaire, and a periodic visit to an HSC. Social and work-related events and health data will be collected from the French national retirement, health and death databases. The data that will be collected include social and demographic characteristics, socioeconomic status, life events, behaviors, and occupational factors. The health data will cover a wide spectrum: self-reported health scales, reported prevalent and incident diseases, long-term chronic diseases and hospitalizations, sick-leaves, handicaps, limitations, disabilities and injuries, healthcare utilization and services provided, and causes of death. To take into account non-participation at inclusion and attrition throughout the longitudinal follow-up, a cohort of non-participants will be set up and followed through the same national databases as participants. A field-pilot was performed in 2010 in seven HSCs, which included about 3,500 subjects; it showed a satisfactory structure of the sample and a good validity of the collected data. DISCUSSION: The constitution of the full eligible sample is planned during the last trimester of 2010, and the cohort will be launched at the beginning of 2011.

Socioeconomic position and low-back pain--the role of biomechanical strains and psychosocial work factors in the GAZEL cohort.

OBJECTIVE: To analyze the role that biomechanical strains and psychosocial work factors play in occupational class disparities in low-back pain in the GAZEL cohort. METHODS: Recruited in 1989, the GAZEL cohort members were employees of the French national company in charge of energy who volunteered to enroll in an annual follow-up survey. The study population comprised 1487 men who completed questionnaires in 1996 (past occupational exposure to manual material handling, bending/twisting, and driving), 1997 (psychosocial work factors), and 2001 (low-back pain using a French version of the Nordic questionnaire for the assessment of low-back pain). Associations between low-back pain for >30 days in the preceding 12 months and social position at baseline (four categories) were described with a Cox model to determine prevalence ratios for each category. We compared adjusted and unadjusted ratios to quantify the contribution of occupational exposures. RESULTS: The prevalence of low-back pain for >30 days was 13.6%. The prevalence of low-back pain adjusted for age was significantly higher for blue-collar workers and clerks than for managers. The number of socioeconomic disparities observed was significantly reduced when biomechanical strains were taken into account; adjusting for psychosocial factors had little impact. CONCLUSION: In this population, occupational exposures--especially biomechanical strains--played an important role in occupational class disparities for persistent or recurrent low-back pain.

Socio-economic status and handedness in two large cohorts of French adults.

Left-and right-handers have coexisted since the Palaeolithic age. Hand preference is heritable. Moreover, there is extensive evidence of an association between left-handedness and several fitness costs. In this context, the persistence of the polymorphism is interesting. Here, we explore the associations between socio-economic status and handedness, analysing data from two large cohorts of adult men and women. Such associations are relevant to an evolutionary approach, as the socio-economic and the reproductive value are related. Our results partly support the hypothesis that left-handers have a socio-economic status advantage, countervailing the health issues. Although the models explain a small proportion of the variance observed, the frequency of left-handedness is significantly higher: (1) among women of higher educational level; (2) among categories of higher income; and (3) among individuals who have a higher position in the company. The importance of these findings for the evolution of the polymorphism of handedness is discussed.

Gender differences in the association between morbidity and mortality among middle-aged men and women.

OBJECTIVES: We examined gender differences in mortality, morbidity, and the association between the 2. METHODS: We used health data from 2 studies of middle-aged men and women: the British Whitehall II cohort of employees from 20 civil service departments in London and the 1989 French GAZEL (this acronym refers to the French gas and electric companies) of employees of France's national gas and electricity company. Participants were aged 35 to 55 years when assessed for morbidity and followed up for mortality over 17 years. RESULTS: Male mortality was higher than female mortality in Whitehall II (hazard ratio [HR] = 1.56; 95% confidence interval [CI] = 1.28, 1.91) and the GAZEL cohort (HR = 1.99; CI = 1.66, 2.40). Female excess morbidity was observed for some measures in the Whitehall II data and for 1 measure in the GAZEL data. Only self-reported sickness absence in the Whitehall II data was more strongly associated with mortality among men (P = .01). CONCLUSIONS: Mortality was lower among women than among men, but morbidity was not consistently higher. The lack of gender differences in the association between morbidity and mortality suggests that this is not a likely explanation for the gender paradox, which refers to higher morbidity but lower mortality among women than among men.