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author:("Vahtera, juss")
1.  Study protocol for examining job strain as a risk factor for severe unipolar depression in an individual participant meta-analysis of 14 European cohorts 
F1000Research  2014;2:233.
Background: Previous studies have shown that gainfully employed individuals with high work demands and low control at work (denoted “job strain”) are at increased risk of common mental disorders, including depression. Most existing studies have, however, measured depression using self-rated symptom scales that do not necessarily correspond to clinically diagnosed depression. In addition, a meta-analysis from 2008 indicated publication bias in the field.
 
Methods: This study protocol describes the planned design and analyses of an individual participant data meta-analysis, to examine whether job strain is associated with an increased risk of clinically diagnosed unipolar depression based on hospital treatment registers.  The study will be based on data from approximately 120,000 individuals who participated in 14 studies on work environment and health in 4 European countries. The self-reported working conditions data will be merged with national registers on psychiatric hospital treatment, primarily hospital admissions. Study-specific risk estimates for the association between job strain and depression will be calculated using Cox regressions. The study-specific risk estimates will be pooled using random effects meta-analysis.
 
Discussion: The planned analyses will help clarify whether job strain is associated with an increased risk of clinically diagnosed unipolar depression. As the analysis is based on pre-planned study protocols and an individual participant data meta-analysis, the pooled risk estimates will not be influenced by selective reporting and publication bias. However, the results of the planned study may only pertain to severe cases of unipolar depression, because of the outcome measure applied.
doi:10.12688/f1000research.2-233.v2
PMCID: PMC3938244  PMID: 24627793
2.  Extending Employment beyond the Pensionable Age: A Cohort Study of the Influence of Chronic Diseases, Health Risk Factors, and Working Conditions 
PLoS ONE  2014;9(2):e88695.
Background
In response to the economic consequences of ageing of the population, governments are seeking ways with which people might work into older age. We examined the association of working conditions and health with extended employment (defined as >6 months beyond the pensionable age) in a cohort of older, non-disabled employees who have reached old-age retirement.
Methods
A total of 4,677 Finnish employees who reached their old-age pensionable date between 2005 and 2011 (mean age 59.8 years in 2005, 73% women) had their survey responses before pensionable age linked to national health and pension registers, resulting in a prospective cohort study.
Results
In all, 832 participants (17.8%) extended their employment by more than 6 months beyond the pensionable date. After multivariable adjustment, the following factors were associated with extended employment: absence of diagnosed mental disorder (OR 1.25, 95% confidence interval = 1.01–1.54) and psychological distress (OR 1.68; 1.35–2.08) and of the work characteristics, high work time control (OR 2.31; 1.88–2.84). The projected probability of extended employment was 21.3% (19.5–23.1) among those free of psychiatric morbidity and with high work time control, while the corresponding probability was only 9.2% (7.4–11.4) among those with both psychiatric morbidity and poor work time control. The contribution of chronic somatic diseases was modest.
Conclusions
In the present study, good mental health in combination with the opportunity to control work time seem to be key factors in extended employment into older age. In addition, high work time control might promote work life participation irrespective of employees' somatic disease status.
doi:10.1371/journal.pone.0088695
PMCID: PMC3929527  PMID: 24586372
3.  Job Strain and the Risk of Inflammatory Bowel Diseases: Individual-Participant Meta-Analysis of 95 000 Men and Women 
PLoS ONE  2014;9(2):e88711.
Background and Aims
Many clinicians, patients and patient advocacy groups believe stress to have a causal role in inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis. However, this is not corroborated by clear epidemiological research evidence. We investigated the association between work-related stress and incident Crohn's disease and ulcerative colitis using individual-level data from 95 000 European adults.
Methods
We conducted individual-participant data meta-analyses in a set of pooled data from 11 prospective European studies. All studies are a part of the IPD-Work Consortium. Work-related psychosocial stress was operationalised as job strain (a combination of high demands and low control at work) and was self-reported at baseline. Crohn's disease and ulcerative colitis were ascertained from national hospitalisation and drug reimbursement registers. The associations between job strain and inflammatory bowel disease outcomes were modelled using Cox proportional hazards regression. The study-specific results were combined in random effects meta-analyses.
Results
Of the 95 379 participants who were free of inflammatory bowel disease at baseline, 111 men and women developed Crohn's disease and 414 developed ulcerative colitis during follow-up. Job strain at baseline was not associated with incident Crohn's disease (multivariable-adjusted random effects hazard ratio: 0.83, 95% confidence interval: 0.48, 1.43) or ulcerative colitis (hazard ratio: 1.06, 95% CI: 0.76, 1.48). There was negligible heterogeneity among the study-specific associations.
Conclusions
Our findings suggest that job strain, an indicator of work-related stress, is not a major risk factor for Crohn's disease or ulcerative colitis.
doi:10.1371/journal.pone.0088711
PMCID: PMC3928274  PMID: 24558416
4.  Living in proximity of a bar and risky alcohol behaviours: A longitudinal study 
Addiction (Abingdon, England)  2012;108(2):320-328.
Aims
We examined whether distance from home to the nearest bar, i.e. alcohol outlet permitting consumption on the premises, is associated with risky alcohol behaviours.
Design
Cross-sectional and longitudinal study.
Setting and Participants
The cross-sectional data consisted of 78 858 and the longitudinal data of 54 778 Finnish Public Sector Study participants in between 2000 and 2009 [mean follow-up 6.8 years (SD=2.0)].
Measurements
Distances from home to the nearest bar were calculated using Global Positioning System-coordinates. The outcome variables were heavy alcohol use (drinking above the weekly guidelines) and extreme drinking occasions (passing out due to alcohol use). We used binomial logistic regression in cross-sectional analyses and in longitudinal mixed effects (between-individual) analyses. Conditional logistic regression was used in longitudinal fixed effects (within-individual) analyses.
Findings
Cross-sectionally, the likelihood of an extreme drinking occasion and heavy use was higher among those who resided <1 vs. ≥1 km from a bar. Longitudinally, between individuals, a decrease from >1 km to ≤1 km in distance was weakly associated with an extreme drinking occasion (1.18, 95% CI 0.98–1.41), and heavy use (1.12, 95% CI 0.97–1.29). Within-individual, the odds ratio for becoming a heavy user was 1.17 (95% CI, 1.02–1.34), per 1 km decrease in log-transformed continuous distance, the corresponding odds ratio for an extreme drinking occasion was 1.03 (95% CI, 0.89–1.18).
Conclusions
Moving place of residence close to or far from a bar appears to be associated with a small corresponding increase or decrease in risky alcohol behaviour.
doi:10.1111/j.1360-0443.2012.04053.x
PMCID: PMC3529803  PMID: 22897634
5.  Depression-Related Work Disability: Socioeconomic Inequalities in Onset, Duration and Recurrence 
PLoS ONE  2013;8(11):e79855.
Objective
Depression is a major cause of disability in working populations and the reduction of socioeconomic inequalities in disability is an important public health challenge. We examined work disability due to depression with four indicators of socioeconomic status.
Methods
A prospective cohort study of 125 355 Finnish public sector employees was linked to national register data on work disability (>9 days) due to depressive disorders (International Classification of Diseases, codes F32–F34) from January 2005 to December 2011. Primary outcomes were the onset of work disability due to depressive disorders and, among those with such disability, return to work after and recurrent episodes of work disability due to depression.
Results
We found a consistent inverse socioeconomic gradient in work disability due to depression. Lower occupational position, lower educational level, smaller residence size, and rented (vs. owner-occupied) residence were all associated with an increased risk of work disability. Return to work was slower for employees with basic education (cumulative odds ratio = 1.21, 95% CI: 1.05–1.39) compared to those with higher education. Recurrent work disability episodes due to depression were less common among upper-grade non-manual workers (the highest occupational group) than among lower-grade non-manual (hazard ratio = 1.16, 95% CI: 1.07–1.25) and manual (hazard ratio = 1.14, 95% CI: 1.02–1.26) workers.
Conclusions
These data from Finnish public sector employees show persistent socioeconomic inequalities in work disability due to depression from 2005 to 2011 in terms of onset, recovery and recurrence.
doi:10.1371/journal.pone.0079855
PMCID: PMC3835932  PMID: 24278194
6.  Influence of retirement on nonadherence to medication for hypertension and diabetes 
Background:
The extent to which common life transitions influence medication adherence among patients remains unknown. We examined whether retirement is associated with a change in adherence to medication in patients with hypertension or type 2 diabetes.
Methods:
Participants in the Finnish Public Sector study were linked to national registers. We included data for the years 1994–2011. We identified and followed 3468 adult patients with hypertension and 412 adult patients with type 2 diabetes for medication adherence for the 3 years before their retirement and the 4 years after their retirement (mean follow-up 6.8 yr). Our primary outcome was proportion of patients with poor adherence to medication, which we defined as less than 40% of days covered by treatment. We determined these proportions before and after retirement using data from filled prescriptions.
Results:
The preretirement prevalence of poor adherence to medication was 6% in men and women with hypertension, 2% in men with diabetes and 4% in women with diabetes. Among men, retirement was associated with an increased risk of poor adherence to both antihypertensive agents (odds ratio [OR] 1.32, 95% confidence interval [CI] 1.03–1.68) and antidiabetic drugs (OR 2.40, 95% CI 1.37–4.20). Among women, an increased risk of poor adherence was seen only for antihypertensive agents (OR 1.25, 95% CI 1.07–1.46). Similar results were apparent for alternative definitions of poor adherence. Our results did not differ across strata of age, socioeconomic status or comorbidity.
Interpretation:
We found a decline in adherence to medication after retirement among men and women with hypertension and men with type 2 diabetes. If these findings can be confirmed, we need randomized controlled trials to determine whether interventions to reduce poor adherence after retirement could improve clinical outcomes of treatments for hypertension and diabetes.
doi:10.1503/cmaj.122010
PMCID: PMC3832579  PMID: 24082018
7.  Study protocol for examining job strain as a risk factor for severe unipolar depression in an individual participant meta-analysis of 14 European cohorts 
F1000Research  2013;2:233.
Background: Previous studies have shown that gainfully employed individuals with high work demands and low control at work (denoted “job strain”) are at increased risk of common mental disorders, including depression. Most existing studies have, however, measured depression using self-rated symptom scales that do not necessarily correspond to clinically diagnosed depression. In addition, a meta-analysis from 2008 indicated publication bias in the field.
 
Methods: This study protocol describes the planned design and analyses of an individual participant data meta-analysis, to examine whether job strain is associated with an increased risk of clinically diagnosed unipolar depression based on hospital treatment registers.  The study will be based on data from approximately 120,000 individuals who participated in 14 studies on work environment and health in 4 European countries. The self-reported working conditions data will be merged with national registers on psychiatric hospital treatment, primarily hospital admissions. Study-specific risk estimates for the association between job strain and depression will be calculated using Cox regressions. The study-specific risk estimates will be pooled using random effects meta-analysis.
 
Discussion: The planned analyses will help clarify whether job strain is associated with an increased risk of clinically diagnosed unipolar depression. As the analysis is based on pre-planned study protocols and an individual participant data meta-analysis, the pooled risk estimates will not be influenced by selective reporting and publication bias. However, the results of the planned study may only pertain to severe cases of unipolar depression, because of the outcome measure applied.
doi:10.12688/f1000research.2-233.v1
PMCID: PMC3938244  PMID: 24627793
8.  Obesity and Occupational Injury: A Prospective Cohort Study of 69,515 Public Sector Employees 
PLoS ONE  2013;8(10):e77178.
Background
Obesity and overweight are suggested to increase the risk of occupational injury but longitudinal evidence to confirm this is rare. We sought to evaluate obesity and overweight as risk factors for occupational injuries.
Methodology/Principal Findings
A total of 69,515 public sector employees (80% women) responded to a survey in 2000–2002, 2004 or 2008. Body mass index (kg/m2) was derived from self-reported height and weight and was linked to records of subsequent occupational injuries obtained from national registers. Different injury types, locations and events or exposures (the manner in which the injury was produced or inflicted) were analyzed by body mass index category adjusting for baseline socio-demographic characteristics, work characteristics, health-risk behaviors, physical and mental health, insomnia symptoms, and sleep duration. During the mean follow-up of 7.8 years (SD = 3.2), 18% of the employees (N = 12,204) recorded at least one occupational injury. Obesity was associated with a higher overall risk of occupational injury; multivariable adjusted hazard ratio (HR) 1.21 (95% CI 1.14–1.27). A relationship was observed for bone fractures (HR = 1.37; 95% CI: 1.10–1.70), dislocations, sprains and strains (HR = 1.36; 95% CI: 1.25–1.49), concussions and internal injuries (HR = 1.26; 95% CI: 1.11–1.44), injuries to lower extremities (HR = 1.62; 95%: 1.46–1.79) and injuries to whole body or multiple sites (HR = 1.37; 95%: 1.10–1.70). Furthermore, obesity was associated with a higher risk of injuries caused by slipping, tripping, stumbling and falling (HR = 1.55; 95% CI: 1.40–1.73), sudden body movement with or without physical stress (HR = 1.24; 95% CI: 1.10–1.41) and shock, fright, violence, aggression, threat or unexpected presence (HR = 1.33; 95% CI: 1.03–1.72). The magnitude of the associations between overweight and injuries was smaller, but the associations were generally in the same direction as those of obesity.
Conclusions/Significance
Obese employees record more occupational injuries than those with recommended healthy weight.
doi:10.1371/journal.pone.0077178
PMCID: PMC3797744  PMID: 24146966
9.  Workplace Determinants of Social Capital: Cross-Sectional and Longitudinal Evidence from a Finnish Cohort Study 
PLoS ONE  2013;8(6):e65846.
Objective
To examine which contextual features of the workplace are associated with social capital.
Methods
This is a cohort study of 43,167 employees in 3090 Finnish public sector workplaces who responded to a survey of individual workplace social capital in 2000–02 (response rate 68%). We used ecometrics approach to estimate social capital of work units. Features of the workplace were work unit's demographic and employment patterns and size, obtained from employers' administrative records. We used multilevel-multinomial logistic regression models to examine cross-sectionally whether these features were associated with social capital between individuals and work units. Fixed effects models were used for longitudinal analyses in a subsample of 12,108 individuals to examine the effects of changes in workplace characteristics on changes in social capital between 2000 and 2004.
Results
After adjustment for individual characteristics, an increase in work unit size reduced the odds of high levels of individual workplace social capital (odds ratio 0.94, 95% confidence interval 0.91–0.98 per 30-person-year increase). A 20% increase in the proportion of manual and male employees reduced the odds of high levels of social capital by 8% and 23%, respectively. A 30% increase in temporary employees and a 20% increase in employee turnover were associated with 11% (95% confidence interval 1.04–1.17) and 24% (95% confidence interval 1.18–1.30) higher odds of having high levels of social capital respectively). Results from fixed effects models within individuals, adjusted for time-varying covariates, and from social capital of the work units yielded consistent results.
Conclusions
These findings suggest that workplace social capital is contextually patterned. Workplace demographic and employment patterns as well as the size of the work unit are important in understanding variations in workplace social capital between individuals and workplaces.
doi:10.1371/journal.pone.0065846
PMCID: PMC3679109  PMID: 23776555
10.  Associations of job strain and lifestyle risk factors with risk of coronary artery disease: a meta-analysis of individual participant data 
Background:
It is unclear whether a healthy lifestyle mitigates the adverse effects of job strain on coronary artery disease. We examined the associations of job strain and lifestyle risk factors with the risk of coronary artery disease.
Methods:
We pooled individual-level data from 7 cohort studies comprising 102 128 men and women who were free of existing coronary artery disease at baseline (1985–2000). Questionnaires were used to measure job strain (yes v. no) and 4 lifestyle risk factors: current smoking, physical inactivity, heavy drinking and obesity. We grouped participants into 3 lifestyle categories: healthy (no lifestyle risk factors), moderately unhealthy (1 risk factor) and unhealthy (2–4 risk factors). The primary outcome was incident coronary artery disease (defined as first nonfatal myocardial infarction or cardiac-related death).
Results:
There were 1086 incident events in 743 948 person-years at risk during a mean follow-up of 7.3 years. The risk of coronary artery disease among people who had an unhealthy lifestyle compared with those who had a healthy lifestyle (hazard ratio [HR] 2.55, 95% confidence interval [CI] 2.18–2.98; population attributable risk 26.4%) was higher than the risk among participants who had job strain compared with those who had no job strain (HR 1.25, 95% CI 1.06–1.47; population attributable risk 3.8%). The 10-year incidence of coronary artery disease among participants with job strain and a healthy lifestyle (14.7 per 1000) was 53% lower than the incidence among those with job strain and an unhealthy lifestyle (31.2 per 1000).
Interpretation:
The risk of coronary artery disease was highest among participants who reported job strain and an unhealthy lifestyle; those with job strain and a healthy lifestyle had half the rate of disease. A healthy lifestyle may substantially reduce disease risk among people with job strain.
doi:10.1503/cmaj.121735
PMCID: PMC3680555  PMID: 23670152
12.  Persistent asthma, co-morbid conditions and the risk of work disability: a prospective cohort study 
Allergy  2011;66(12):1598-1603.
Backround
This study examined whether asthma alone or together with chronic co-morbidity is associated with increased risk of long-term work disability.
Methods
We examined data from 2,332 asthmatic and 66,354 non-asthmatic public sector employees in Finland who responded to a survey between 1997 and 2004. Respondents were coded as persistent asthmatics based on the special reimbursement for continuous asthma medication by the Social Insurance Institution. Data on long-term work disability (sickness absences or disability pensions >90 days) were obtained from national registers. The risk of work disability was examined by Cox proportional hazard models adjusted for age, gender, socioeconomic status, type of employment contract and type of employer.
Results
Asthma increased the risk of all-cause long-term work disability, hazard ratio (HR) 1.8 (95 % CI 1.62–2.09) compared to controls (no asthma). Asthma and one other chronic co-morbidity increased the risk for long-term all-cause work disability with HR 2.2 (95% CI 1.78–2.83). Asthma together with two or more other chronic conditions increased the risk with HR 4.5 (95% CI 2.98–6.78). Asthma and depression increased the risk with HR 3.6 and the risk was especially high for permanent work-disability (HR 6.8). Among those with asthma there were more women, obesity (BMI ≥30), ex-smokers and lower-grade non-manual workers.
Conclusions
Asthma is associated with increased risk of long-term all-cause work disability. The risk increases further with chronic co-morbidities, and is especially high in patients with asthma and depression.
doi:10.1111/j.1398-9995.2011.02729.x
PMCID: PMC3203316  PMID: 21958351
Asthma; co-morbidity; sickness absence; work disability
13.  Job Strain as a Risk Factor for Leisure-Time Physical Inactivity: An Individual-Participant Meta-Analysis of Up to 170,000 Men and Women 
American Journal of Epidemiology  2012;176(12):1078-1089.
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.
doi:10.1093/aje/kws336
PMCID: PMC3521479  PMID: 23144364
cohort studies; exercise; physical activity; psychosocial factors; working population
14.  Childhood adversities and adult-onset asthma: a cohort study 
BMJ Open  2012;2(5):e001625.
Objectives
Childhood adversities may be important determinants of later illnesses and poor health behaviour. However, large-scale prospective studies on the associations between childhood adversities and the onset of asthma in adulthood are lacking.
Design
Prospective cohort study with 7-year follow-up.
Setting
Nationally representative study. Data were collected from the Health and Social Support (HeSSup) survey and national registers.
Participants
The participants represent the Finnish population from the following age groups: 20–24, 30–34, 40–44, and 50–54 years at baseline in 1998 (24 057 survey participants formed the final cohort of this study). The occurrence of childhood adversities was assessed at baseline with a six-item survey scale. The analyses were adjusted for sociodemographic characteristics, behavioural health risks and common mental disorders.
Primary and secondary outcomes
The survey data were linked to data from national health registers on incident asthma during a 7-year follow-up to define new-onset asthma cases with verified diagnoses.
Results
A total of 12 126 (59%) participants reported that they encountered a childhood adversity. Of them 3677 (18% of all) endured three to six adversities. During a follow-up of 7 years, 593 (2.9%) participants were diagnosed with incident asthma. Those who reported three or more childhood adversities had a 1.6-fold (95% CI 1.31 to 2.01) greater risk of asthma compared to those without childhood adversities. This hazard attenuated but remained statistically significant after adjustment for conventional risk factors (HR 1.33; 95% CI 1.06 to 1.67).
Conclusions
Adults who report having encountered adversities in childhood may have an increased risk of developing asthma.
doi:10.1136/bmjopen-2012-001625
PMCID: PMC3488721  PMID: 23069774
Psychiatry; Epidemiology
15.  Differences in the association between sickness absence and long-term sub-optimal health by occupational position: a 14-year follow-up in the GAZEL cohort 
Objectives
Although sickness absence is a strong predictor of health, little work has examined whether this association varies by occupational position. The aim of this study was to investigate overall and diagnosis-specific sickness absence as a predictor of future long-term sub-optimal health by occupational position.
Methods
Prospective occupational cohort study; 15,320 employees (73% men) aged 37–51. Sickness absences (1990–1992), including 13 diagnostic categories, were examined by occupational position, based on employment grade, in relation to self-rated health measured annually 1993–2006.
Results
60% of employees in higher grade and 22% in lower grade occupations had no sickness absence. Conversely, 40% of employees in lower grade and 9.5% in higher grade occupations had over 30 sick-leave days. Repeated-measures logistic regression analyses adjusted for age, sex, and chronic disease showed employees with over 30 days absence, compared to those with no absence, had approximately double the risk of suboptimal health over the 14-year follow-up in all occupational positions. However, 1–30 days sick-leave was associated with greater odds of suboptimal health in the high; odds ratio 1.48, 95% confidence intervals (1.27–1.72) and intermediate 1.29 (1.15–1.45), but not lower grade occupations 1.06 (0.82–1.38). Differences by occupational position in the association between sickness absence in 13 specific diagnostic categories and sub-optimal health over the ensuing 14 years were limited to stronger associations observed with cancer and mental disorders in the higher grades.
Conclusions
The association between sickness absence of over 30 days a year and future long-term self-rated health appears to differ little by occupational position.
doi:10.1136/oem.2010.060210
PMCID: PMC3186885  PMID: 21242277
Sickness absence; sick leave; self-rated health; longitudinal; multi-level; occupational position
16.  Associations between Nighttime Traffic Noise and Sleep: The Finnish Public Sector Study 
Environmental Health Perspectives  2012;120(10):1391-1396.
Background: Associations between traffic noise and sleep problems have been detected in experimental studies, but population-level evidence is scarce.
Objectives: We studied the relationship between the levels of nighttime traffic noise and sleep disturbances and identified vulnerable population groups.
Methods: Noise levels of nighttime–outdoor traffic were modeled based on the traffic intensities in the cities of Helsinki and Vantaa, Finland. In these cities, 7,019 public sector employees (81% women) responded to postal surveys on sleep and health. We linked modeled outdoor noise levels to the residences of the employees who responded to the postal survey. We used logistic regression models to estimate associations of noise levels with subjectively assessed duration of sleep and symptoms of insomnia (i.e., difficulties falling asleep, waking up frequently during the night, waking up too early in the morning, nonrestorative sleep). We also used stratified models to investigate the possibility of vulnerable subgroups.
Results: For the total study population, exposure to levels of nighttime–outside (Lnight, outside) traffic noise > 55 dB was associated with any insomnia symptom ≥ 2 nights per week [odds ratio (OR) = 1.32; 95% confidence interval (CI): 1.05, 1.65]. Among participants with higher trait anxiety scores, which we hypothesized were a proxy for noise sensitivity, the ORs for any insomnia symptom at exposures to Lnight, outside traffic noises 50.1–55 dB and > 55 dB versus ≤ 45 dB were 1.34 (95% CI: 1.00, 1.80) and 1.61 (95% CI: 1.07, 2.42), respectively.
Conclusions: Nighttime traffic noise levels > 50 dB Lnight, outside was associated with insomnia symptoms among persons with higher scores for trait anxiety. For the total study population, Lnight, outside > 55 dB was positively associated with any symptoms.
doi:10.1289/ehp.1205026
PMCID: PMC3491945  PMID: 22871637
cohort study; epidemiology; sleep disturbance; traffic noise
17.  Job strain as a risk factor for coronary heart disease: a collaborative meta-analysis of individual participant data 
Lancet  2012;380(9852):1491-1497.
Summary
Background
Published work assessing psychosocial stress (job strain) as a risk factor for coronary heart disease is inconsistent and subject to publication bias and reverse causation bias. We analysed the relation between job strain and coronary heart disease with a meta-analysis of published and unpublished studies.
Methods
We used individual records from 13 European cohort studies (1985–2006) of men and women without coronary heart disease who were employed at time of baseline assessment. We measured job strain with questions from validated job-content and demand-control questionnaires. We extracted data in two stages such that acquisition and harmonisation of job strain measure and covariables occurred before linkage to records for coronary heart disease. We defined incident coronary heart disease as the first non-fatal myocardial infarction or coronary death.
Findings
30 214 (15%) of 197 473 participants reported job strain. In 1·49 million person-years at risk (mean follow-up 7·5 years [SD 1·7]), we recorded 2358 events of incident coronary heart disease. After adjustment for sex and age, the hazard ratio for job strain versus no job strain was 1·23 (95% CI 1·10–1·37). This effect estimate was higher in published (1·43, 1·15–1·77) than unpublished (1·16, 1·02–1·32) studies. Hazard ratios were likewise raised in analyses addressing reverse causality by exclusion of events of coronary heart disease that occurred in the first 3 years (1·31, 1·15–1·48) and 5 years (1·30, 1·13–1·50) of follow-up. We noted an association between job strain and coronary heart disease for sex, age groups, socioeconomic strata, and region, and after adjustments for socioeconomic status, and lifestyle and conventional risk factors. The population attributable risk for job strain was 3·4%.
Interpretation
Our findings suggest that prevention of workplace stress might decrease disease incidence; however, this strategy would have a much smaller effect than would tackling of standard risk factors, such as smoking.
Funding
Finnish Work Environment Fund, the Academy of Finland, the Swedish Research Council for Working Life and Social Research, the German Social Accident Insurance, the Danish National Research Centre for the Working Environment, the BUPA Foundation, the Ministry of Social Affairs and Employment, the Medical Research Council, the Wellcome Trust, and the US National Institutes of Health.
doi:10.1016/S0140-6736(12)60994-5
PMCID: PMC3486012  PMID: 22981903
18.  Differences in the association between sickness absence and long-term sub-optimal health by occupational position: a 14-year follow-up in the GAZEL cohort 
Objectives
Although sickness absence is a strong predictor of health, little work has examined whether this association varies by occupational position. The aim of this study was to investigate overall and diagnosis-specific sickness absence as a predictor of future long-term sub-optimal health by occupational position.
Methods
Prospective occupational cohort study; 15,320 employees (73% men) aged 37–51. Sickness absences (1990–1992), including 13 diagnostic categories, were examined by occupational position, in relation to self-rated health measured annually 1993–2006.
Results
60% of employees in higher occupational position and 22% in lower position had no sickness absence. Conversely, 9.5% of employees in higher position and 40% in lower occupational position had over 30 sick-leave days. Repeated-measures logistic regression analyses adjusted for age, sex, and chronic disease showed employees with over 30 days absence, compared to those with no absence, had approximately double the risk of suboptimal health over the 14-year follow-up in all occupational positions. However, 1–30 days sick-leave was associated with greater odds of suboptimal health in the high; odds ratio 1.48, 95% confidence intervals (1.27–1.72) and intermediate 1.29 (1.15–1.45), but not lower occupational positions 1.06 (0.82–1.38). Differences by occupational position in the association between sickness absence in 13 specific diagnostic categories and sub-optimal health over the ensuing 14 years were limited to stronger associations observed with cancer and mental disorders in the higher occupational positions.
Conclusions
The association between sickness absence of over 30 days a year and future long-term self-rated health appears to differ little by occupational position.
doi:10.1136/oem.2010.060210
PMCID: PMC3186885  PMID: 21242277
Adult; Female; Follow-Up Studies; France; epidemiology; Health Status; Humans; Male; Middle Aged; Occupational Diseases; epidemiology; Occupational Health; statistics & numerical data; Occupations; Prospective Studies; Risk Factors; Sick Leave; statistics & numerical data; Social Class; Sickness absence; sick leave; health; longitudinal; multi-level; occupational position
19.  Environmental Stress Affects DNA Methylation of a CpG Rich Promoter Region of Serotonin Transporter Gene in a Nurse Cohort 
PLoS ONE  2012;7(9):e45813.
Background
Shift-working nurses are exposed to a stressful work environment, which puts them at an increased risk for burnout and depression. We explored the effect of environmental stress on serotonin transporter gene (SLC6A4) promoter methylation among nurses from high and low work stress environments.
Methodology
Using bisulfite sequencing, we investigated the methylation status of five CpG residues of a CpG-rich region in the promoter of SLC6A4 by comparing female shift working nurses from a high work stress environment (n = 24) to low work stress environment (n = 25). We also analyzed the association of 5-HTTLPR polymorphism at 5′ end of SLC6A4. Work stress was assessed by the Karasek’s Model and possible signs of burnout or depression were measured by the Maslach Burnout Index General Survey and Beck Depression Index. Methylation levels were assessed by bisulfite sequencing of DNA extracted from peripheral blood leucocytes. Restriction enzyme treatment followed by standard PCR was used to identify 5-HTTLPR genotypes.
Principal Findings
We found that nurses in the high stress environment had significantly lower promoter methylation levels at all five CpG residues compared to nurses in the low stress environment (p<0.01). There was no significant interaction of 5-HTTLPR genotype and work stress with methylation (p = 0.58). In unadjusted (bivariate) analysis, burnout was not significantly associated to methylation levels. However, when mutually adjusted for both, burnout and work stress were significant contributors (p = 0.038 and p<0.0001 respectively) to methylation levels.
Conclusions
Our findings show that environmental stress is concurrent with decreased methylation of the SLC6A4 promoter. This may lead to increased transcriptional activity of the gene, increased reuptake of serotonin from synaptic clefts, and termination of the activity of serotonin. This could present a possible coping mechanism for environmental stress in humans that could eventually increase risk for disturbed functional capability and experience of depressed mood in long-term stress.
doi:10.1371/journal.pone.0045813
PMCID: PMC3461019  PMID: 23029256
20.  School environment as predictor of teacher sick leave: data-linked prospective cohort study 
BMC Public Health  2012;12:770.
Background
Poor indoor air quality (IAQ) and psychosocial problems are common in schools worldwide, yet longitudinal research on the issue is scarce. We examined whether the level of or a change in pupil-reported school environment (IAQ, school satisfaction, and bullying) predicts recorded sick leaves among teachers.
Methods
Changes in the school environment were assessed using pupil surveys at two time points (2001/02 and 2004/05) in 92 secondary schools in Finland. Variables indicating change were based on median values at baseline. We linked these data to individual-level records of teachers’ (n = 1678) sick leaves in 2001–02 and in 2004–05.
Results
Multilevel multinomial logistic regression models adjusted for baseline sick leave and covariates showed a decreased risk for short-term (one to three days) sick leaves among teachers working in schools with good perceived IAQ at both times (OR = 0.6, 95% CI: 0.5-0.9), and for those with a positive change in IAQ (OR = 0.6, 95% CI: 0.4-0.9), compared to teachers in schools where IAQ was constantly poor. Negative changes in pupil school satisfaction (OR = 1.8, 95% CI: 1.1-2.8) and bullying (OR = 1.5, 95% CI: 1.0-2.3) increased the risk for short-term leaves among teachers when compared to teachers in schools where the level of satisfaction and bullying had remained stable. School environment factors were not associated with long-term sick leaves.
Conclusions
Good and improved IAQ are associated with decreased teacher absenteeism. While pupil-related psychosocial factors also contribute to sick leaves, no effect modification or mediation of psychosocial factors on the association between IAQ and sick leave was observed.
doi:10.1186/1471-2458-12-770
PMCID: PMC3490775  PMID: 22966903
Bullying; Multilevel; Perceived indoor air; School satisfaction; Ventilation
21.  Long Working Hours and Coronary Heart Disease: A Systematic Review and Meta-Analysis 
American Journal of Epidemiology  2012;176(7):586-596.
The authors aggregated the results of observational studies examining the association between long working hours and coronary heart disease (CHD). Data sources used were MEDLINE (through January 19, 2011) and Web of Science (through March 14, 2011). Two investigators independently extracted results from eligible studies. Heterogeneity between the studies was assessed using the I2 statistic, and the possibility of publication bias was assessed using the funnel plot and Egger's test for small-study effects. Twelve studies were identified (7 case-control, 4 prospective, and 1 cross-sectional). For a total of 22,518 participants (2,313 CHD cases), the minimally adjusted relative risk of CHD for long working hours was 1.80 (95% confidence interval (CI): 1.42, 2.29), and in the maximally (multivariate-) adjusted analysis the relative risk was 1.59 (95% CI: 1.23, 2.07). The 4 prospective studies produced a relative risk of 1.39 (95% CI: 1.12, 1.72), while the corresponding relative risk in the 7 case-control studies was 2.43 (95% CI: 1.81, 3.26). Little evidence of publication bias but relatively large heterogeneity was observed. Studies varied in size, design, measurement of exposure and outcome, and adjustments. In conclusion, results from prospective observational studies suggest an approximately 40% excess risk of CHD in employees working long hours.
doi:10.1093/aje/kws139
PMCID: PMC3458589  PMID: 22952309
cardiovascular diseases; coronary disease; employment; meta-analysis; myocardial infarction; review; work
22.  Workplace social capital and all-cause mortality: A prospective cohort study of 28,043 public sector employees 
American Journal of Public Health  2011;101(9):1742-1748.
Objective
To examine the association between workplace social capital and all-cause mortality in a large occupational cohort from Finland.
Methods
Responses of 28,043 participants to surveys in 2000–2002 and 2004 were linked to national mortality registers through 2009. We used repeated measurements of self-assessed and co-workers' assessed workplace social capital. Cox proportional hazard and fixed effects logistic regressions were conducted.
Results
196 employees died during the 5-year follow-up period. A one unit increase in the mean of repeat measurements of self-assessed workplace social capital (range 1–5) was associated with a 19% decrease in the risk of all-cause mortality [age- and sex-adjusted HR=0.81; 95% CI 0.66–0.99]. The corresponding point estimate for the mean of co-workers' assessed social capital was similar, although the association was more imprecisely estimated [age- and sex-adjusted HR=0.77; 95% CI 0.50–1.20]. In fixed-effects analysis, a one unit increase in self-assessed social capital across the two time points was associated with a lower mortality risk (OR=0.81, 95% CI 0.55–1.19).
Conclusion
These findings suggest that workplace social capital is associated with decreased risk of mortality in the working-age population.
doi:10.2105/AJPH.2011.300166
PMCID: PMC3154232  PMID: 21778502
social capital; mortality; cohort study
23.  Job Strain and Tobacco Smoking: An Individual-Participant Data Meta-Analysis of 166 130 Adults in 15 European Studies 
PLoS ONE  2012;7(7):e35463.
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.
doi:10.1371/journal.pone.0035463
PMCID: PMC3391192  PMID: 22792154
24.  Job Strain and Alcohol Intake: A Collaborative Meta-Analysis of Individual-Participant Data from 140 000 Men and Women 
PLoS ONE  2012;7(7):e40101.
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.
doi:10.1371/journal.pone.0040101
PMCID: PMC3391232  PMID: 22792218
25.  Is retirement beneficial for mental health? Antidepressant use before and after retirement 
Epidemiology (Cambridge, Mass.)  2011;22(4):553-559.
Background
Recent studies based on self-reported data suggest that retirement may have beneficial effects on mental health, but studies using objective endpoints remain scarce. This study examines longitudinally the changes in antidepressant medication use across the 9 years spanning the transition to retirement.
Methods
Participants were Finnish public-sector employees: 7138 retired at statutory retirement age (76% women, mean age 61.2 years), 1238 retired early due to mental health issues (78% women, mean age 52.0 years), and 2643 retired due to physical health issues(72% women, mean age 55.4 years). Purchase of antidepressant medication four years prior to and four years after retirement year were based on comprehensive national pharmacy records in 1994-2005.
Results
One year before retirement, the use of antidepressants was 4% among those who would retire at statutory age, 61% among those who would retire due to mental health issues, and 14% among those who would retire due to physical health issues. Retirement-related changes in antidepressant use depended on the reason for retirement. Among old-age retirees, antidepressant medication use decreased during the transition period (age- and calendar-year-adjusted prevalence ratio for antidepressant use 1 year after vs. 1 year before retirement = 0.77 [95% confidence interval = 0.68 – 0.88]). Among those whose main reason for disability pension was mental health issues or physical health issues, there was an increasing trend in antidepressant use prior to retirement and, for mental health retirements, a decrease after retirement.
Conclusions
Trajectories of recorded purchases of antidepressant medication are consistent with the hypothesis that retirement is beneficial for mental health.
doi:10.1097/EDE.0b013e31821c41bd
PMCID: PMC3132597  PMID: 21502864

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