The effect of exposure to long working hours on ischaemic heart disease: A systematic review and meta-analysis from the WHO/ILO Joint Estimates of the Work-related Burden of Disease and Injury.

BACKGROUND: The World Health Organization (WHO) and the International Labour Organization (ILO) are developing Joint Estimates of the work-related burden of disease and injury (WHO/ILO Joint Estimates), with contributions from a large network of experts. Evidence from mechanistic data suggests that exposure to long working hours may cause ischaemic heart disease (IHD). In this paper, we present a systematic review and meta-analysis of parameters for estimating the number of deaths and disability-adjusted life years from IHD that are attributable to exposure to long working hours, for the development of the WHO/ILO Joint Estimates. OBJECTIVES: We aimed to systematically review and meta-analyse estimates of the effect of exposure to long working hours (three categories: 41-48, 49-54 and ≥55 h/week), compared with exposure to standard working hours (35-40 h/week), on IHD (three outcomes: prevalence, incidence and mortality). DATA SOURCES: We developed and published a protocol, applying the Navigation Guide as an organizing systematic review framework where feasible. We searched electronic databases for potentially relevant records from published and unpublished studies, including MEDLINE, Scopus, Web of Science, CISDOC, PsycINFO, and WHO ICTRP. We also searched grey literature databases, Internet search engines and organizational websites; hand-searched reference lists of previous systematic reviews; and consulted additional experts. STUDY ELIGIBILITY AND CRITERIA: We included working-age (≥15 years) workers in the formal and informal economy in any WHO and/or ILO Member State but excluded children (aged < 15 years) and unpaid domestic workers. We included randomized controlled trials, cohort studies, case-control studies and other non-randomized intervention studies which contained an estimate of the effect of exposure to long working hours (41-48, 49-54 and ≥55 h/week), compared with exposure to standard working hours (35-40 h/week), on IHD (prevalence, incidence or mortality). STUDY APPRAISAL AND SYNTHESIS METHODS: At least two review authors independently screened titles and abstracts against the eligibility criteria at a first stage and full texts of potentially eligible records at a second stage, followed by extraction of data from qualifying studies. Missing data were requested from principal study authors. We combined relative risks using random-effect meta-analysis. Two or more review authors assessed the risk of bias, quality of evidence and strength of evidence, using Navigation Guide and GRADE tools and approaches adapted to this project. RESULTS: Thirty-seven studies (26 prospective cohort studies and 11 case-control studies) met the inclusion criteria, comprising a total of 768,751 participants (310,954 females) in 13 countries in three WHO regions (Americas, Europe and Western Pacific). The exposure was measured using self-reports in all studies, and the outcome was assessed with administrative health records (30 studies) or self-reported physician diagnosis (7 studies). The outcome was defined as incident non-fatal IHD event in 19 studies (8 cohort studies, 11 case-control studies), incident fatal IHD event in two studies (both cohort studies), and incident non-fatal or fatal ("mixed") event in 16 studies (all cohort studies). Because we judged cohort studies to have a relatively lower risk of bias, we prioritized evidence from these studies and treated evidence from case-control studies as supporting evidence. For the bodies of evidence for both outcomes with any eligible studies (i.e. IHD incidence and mortality), we did not have serious concerns for risk of bias (at least for the cohort studies). No eligible study was found on the effect of long working hours on IHD prevalence. Compared with working 35-40 h/week, we are uncertain about the effect on acquiring (or incidence of) IHD of working 41-48 h/week (relative risk (RR) 0.98, 95% confidence interval (CI) 0.91 to 1.07, 20 studies, 312,209 participants, I2 0%, low quality of evidence) and 49-54 h/week (RR 1.05, 95% CI 0.94 to 1.17, 18 studies, 308,405 participants, I2 0%, low quality of evidence). Compared with working 35-40 h/week, working ≥55 h/week may have led to a moderately, clinically meaningful increase in the risk of acquiring IHD, when followed up between one year and 20 years (RR 1.13, 95% CI 1.02 to 1.26, 22 studies, 339,680 participants, I2 5%, moderate quality of evidence). Compared with working 35-40 h/week, we are very uncertain about the effect on dying (mortality) from IHD of working 41-48 h/week (RR 0.99, 95% CI 0.88 to 1.12, 13 studies, 288,278 participants, I2 8%, low quality of evidence) and 49-54 h/week (RR 1.01, 95% CI 0.82 to 1.25, 11 studies, 284,474 participants, I2 13%, low quality of evidence). Compared with working 35-40 h/week, working ≥55 h/week may have led to a moderate, clinically meaningful increase in the risk of dying from IHD when followed up between eight and 30 years (RR 1.17, 95% CI 1.05 to 1.31, 16 studies, 726,803 participants, I2 0%, moderate quality of evidence). Subgroup analyses found no evidence for differences by WHO region and sex, but RRs were higher among persons with lower SES. Sensitivity analyses found no differences by outcome definition (exclusively non-fatal or fatal versus "mixed"), outcome measurement (health records versus self-reports) and risk of bias ("high"/"probably high" ratings in any domain versus "low"/"probably low" in all domains). CONCLUSIONS: We judged the existing bodies of evidence for human evidence as "inadequate evidence for harmfulness" for the exposure categories 41-48 and 49-54 h/week for IHD prevalence, incidence and mortality, and for the exposure category ≥55 h/week for IHD prevalence. Evidence on exposure to working ≥55 h/week was judged as "sufficient evidence of harmfulness" for IHD incidence and mortality. Producing estimates for the burden of IHD attributable to exposure to working ≥55 h/week appears evidence-based, and the pooled effect estimates presented in this systematic review could be used as input data for the WHO/ILO Joint Estimates.

WHO/ILO work-related burden of disease and injury: Protocol for systematic reviews of exposure to long working hours and of the effect of exposure to long working hours on ischaemic heart disease.

BACKGROUND: The World Health Organization (WHO) and the International Labour Organization (ILO) are developing a joint methodology for estimating the national and global work-related burden of disease and injury (WHO/ILO joint methodology), with contributions from a large network of experts. In this paper, we present the protocol for two systematic reviews of parameters for estimating the number of deaths and disability-adjusted life years of ischaemic heart disease from exposure to long working hours, to inform the development of the WHO/ILO joint methodology. OBJECTIVES: We aim to systematically review studies on occupational exposure to long working hours (Systematic Review 1) and systematically review and meta-analyse estimates of the effect of long working hours on ischaemic heart disease (Systematic Review 2), applying the Navigation Guide systematic review methodology as an organizing framework. The selection of both, the exposure and the health outcome is justified by substantial scientific evidence on adverse effects of long working hours on ischaemic heart disease risk. DATA SOURCES: Separately for Systematic Reviews 1 and 2, we will search electronic academic databases for potentially relevant records from published and unpublished studies, Medline, EMBASE, Web of Science, CISDOC and PsychINFO. We will also search electronic grey literature databases, Internet search engines and organizational websites; hand-search reference list of previous systematic reviews and included study records; and consult additional experts. STUDY ELIGIBILITY AND CRITERIA: We will include working-age (≥15 years) workers in the formal and informal economy in any WHO and/or ILO Member State, but exclude children (<15 years) and unpaid domestic workers. For Systematic Review 1, we will include quantitative prevalence studies of relevant levels of exposure to long working hours (i.e. 35-40, 41-48, 49-54 and ≥55 h/week) stratified by country, sex, age and industrial sector or occupation. For Systematic Review 2, we will include randomized controlled trials, cohort studies, case-control studies and other non-randomized intervention studies with an estimate of the relative effect of relevant level(s) of long working hours on the prevalence of, incidence of or mortality from ischaemic heart disease, compared with the theoretical minimum risk exposure level (i.e. 35-40 h/week). STUDY APPRAISAL AND SYNTHESIS METHODS: At least two review authors will independently screen titles and abstracts against the eligibility criteria at a first stage and full texts of potentially eligible records at a second stage, followed by extraction of data from qualifying studies. At least two review authors will assess risk of bias and the quality of evidence, using the most suited tools currently available. For Systematic Review 2, if feasible, we will combine relative risks using meta-analysis. We will report results using the guidelines for accurate and transparent health estimates reporting (GATHER) for Systematic Review 1 and the preferred reporting items for systematic reviews and meta-analyses guidelines (PRISMA) for Systematic Review 2. PROSPERO registration number: CRD42017084243.

Work organization, health, and obesity in urban transit operators: A qualitative study.

BACKGROUND: Urban transit operators have high rates of obesity, hypertension, and other cardiovascular risk-factors compared to other occupations. There have been few qualitative studies exploring the interrelationships between the organization of transit work, stress, and health including obesity, from the perspective of operators. METHODS: Five focus groups were conducted at five Divisions in a transit authority in Southern California and included 65 bus and rail operators. RESULTS: Operators reported a great deal of stress related to their work, including 1) time pressures and lack of recovery time; 2) long work shifts and overtime; 3) feeling unsafe when dealing with the public; 4) lack of respect from supervisors and management. Operators believed stressful working conditions negatively impacted their health and weight. CONCLUSION: This qualitative study yielded new as well as confirmatory data about stress and transit work organization, health, and weight in operators. This study will add to future survey research and interventions in this population.

Globalization, Work, and Cardiovascular Disease.

Cardiovascular disease (CVD), a global epidemic, is responsible for about 30% of all deaths worldwide. While mortality rates from CVD have been mostly declining in the advanced industrialized nations, CVD risk factors, including hypertension, obesity, and diabetes, have been on the increase everywhere. Researchers investigating the social causes of CVD have produced a robust body of evidence documenting the relationships between the work environment and CVD, including through the mechanisms of psychosocial work stressors. We review the empirical evidence linking work, psychosocial stressors, and CVD. These work stressors can produce chronic biologic arousal and promote unhealthy behaviors and thus, increased CVD risk. We offer a theoretical model that illustrates how economic globalization influences the labor market and work organization in high-income countries, which, in turn, exacerbates job characteristics, such as demands, low job control, effort-reward imbalance, job insecurity, and long work hours. There is also a growing interest in "upstream" factors among work stress researchers, including precarious employment, downsizing/restructuring, privatization, and lean production. We conclude with suggestions for future epidemiologic research on the role of work in the development of CVD, as well as policy recommendations for prevention of work-related CVD.

Short-term test-retest reliability of the Job Content Questionnaire and Effort-Reward Imbalance Questionnaire items and scales among professional firefighters.

Relatively little is known about the short-term test-retest reliability of the Job Content Questionnaire (JCQ) and Effort-Reward Imbalance Questionnaire (ERIQ). Seventeen JCQ and six ERIQ items were qualitatively reviewed by 19 firefighters in focus groups. The items were then administered twice to 81 firefighters with a time interval of 1-8 weeks. The short-term reliability of the JCQ and ERIQ items and scales with the four-point Likert item responses was at least fair or moderate with several complementary statistical methods. It improved substantially when the four-point responses were simplified into the two ('agree' or 'disagree') responses. The JCQ psychological demands and the ERIQ effort scales were among the least reliable scales and their items were most frequently indicated by the firefighters to be clarified. The responses of professional firefighters to the JCQ and ERIQ items and scales were stable during an 8-week period, particularly when dichotomous item responses were used.

Very Long (> 48 hours) Shifts and Cardiovascular Strain in Firefighters: a Theoretical Framework.

Shift work and overtime have been implicated as important work-related risk factors for cardiovascular disease (CVD). Many firefighters who contractually work on a 24-hr work schedule, often do overtime (additional 24-hr shifts) which can result in working multiple, consecutive 24-hr shifts. Very little research has been conducted on firefighters at work that examines the impact of performing consecutive 24-hr shifts on cardiovascular physiology. Also, there have been no standard field methods for assessing in firefighters the cardiovascular changes that result from 24-hr shifts, what we call "cardiovascular strain". The objective of this study, as the first step toward elucidating the role of very long (> 48 hrs) shifts in the development of CVD in firefighters, is to develop and describe a theoretical framework for studying cardiovascular strain in firefighters on very long shifts (i.e., > 2 consecutive 24-hr shifts). The developed theoretical framework was built on an extensive literature review, our recently completed studies with firefighters in Southern California, e-mail and discussions with several firefighters on their experiences of consecutive shifts, and our recently conducted feasibility study in a small group of firefighters of several ambulatory cardiovascular strain biomarkers (heart rate, heart rate variability, blood pressure, salivary cortisol, and salivary C-reactive protein). The theoretical framework developed in this study will facilitate future field studies on consecutive 24-hr shifts and cardiovascular health in firefighters. Also it will increase our understanding of the mechanisms by which shift work or long work hours can affect CVD, particularly through CVD biological risk factors, and thereby inform policy about sustainable work and rest schedules for firefighters.

Working conditions and masked hypertension.

INTRODUCTION: Masked hypertension, i.e., normal clinic blood pressure but elevated blood pressure during normal daily activities as measured by ambulatory monitoring, is a common problem and a serious cardiovascular risk factor. Given previously reported associations between work stressors and ambulatory blood pressure, an inquiry into the relationship between work stressors and masked hypertension is warranted. OBJECTIVE: To assess the relationship between working conditions and masked hypertension. DESIGN: Cross-sectional study. SETTING: Hospital and home care employers in New York City. STUDY PARTICIPANTS: Forty-five male and 119 female hospital and home care employee volunteers wore an ambulatory blood pressure monitor during working hours. MAIN OUTCOME MEASURES: Masked hypertension was defined as work systolic ambulatory blood pressure ≥135 mmHg or diastolic ambulatory blood pressure ≥85 mmHg, and casual blood pressure <140/90 mmHg with no use of antihypertensive medications. Associations between work stressors and masked hypertension were tested by multiple logistic regression. RESULTS: Masked hypertension, observed in 24.0% of males and 17.6% of females with normal casual office obtained blood pressure, was associated with evening, night or rotating shiftwork (odds ratio (OR) 8.25, 95% confidence interval (CI) 2.11-40.31) and with the combination of job strain and effort-reward imbalance (OR 2.97, 95% CI 1.02-8.60) after controlling for age. Associations remained substantial, and statistically significant for shiftwork, after individual adjustment for each of 10 potential confounders. Masked hypertension was not associated with total weekly work hours. CONCLUSIONS: Masked hypertension is a significant individual and public health concern. Additional research is needed to clarify the role of work-related risk factors in the development of masked hypertension, and to develop an appropriate clinical and public health strategy for diagnosis, treatment and prevention.

Exploring occupational and health behavioral causes of firefighter obesity: a qualitative study.

BACKGROUND: Firefighters, as an occupational group, have one of the highest prevalence rates of obesity. A qualitative study investigated occupational and health behavioral determinants of obesity among firefighters. METHODS: Four focus groups were conducted with firefighters of every rank as Phase I of the FORWARD study which was designed to assess health behavioral and occupational characteristics related to obesity in firefighters. RESULTS: Analysis revealed five main themes of central importance to firefighters: (1) fire station eating culture; (2) night calls and sleep interruption; (3) supervisor leadership and physical fitness; (4) sedentary work; and (5) age and generational influences. CONCLUSION: The results showed a strong interrelationship between occupational and health behavioral causes of obesity in firefighters. The relevance of these qualitative findings are discussed along with the implications for future obesity interventions with firefighters.

Psychosocial working conditions and active leisure-time physical activity in middle-aged us workers.

OBJECTIVES: This study was to examine whether psychosocial work characteristics such as job control, psychological job demands, and their combinations are associated with leisure-time physical activity (LTPA) in US workers. MATERIALS AND METHODS: 2019 workers (age range: 32 to 69) from the National Survey of Midlife Development in the United States (MIDUS) II study (2004-2006) were chosen for this cross-sectional study. Job control and job demands were measured by standard questionnaire items. Active LTPA was defined as "moderate or vigorous" level of physical activity. RESULTS: After controlling for covariates (e.g., age, race, education, income, physical effort at work, obesity, and alcohol consumption), high job control was associated with active LTPA. Active jobs (high control and low demands) and low-strain jobs (high control and high demands), compared to passive jobs (low control and low demands), increased the odds for active LTPA. The associations varied by sex and education level. Job demands alone were not associated with active LTPA. CONCLUSIONS: Having on-the-job learning opportunities and decision authority on their tasks may be conducive to active LTPA in middle-aged US workers.

Sedentary work, low physical job demand, and obesity in US workers.

BACKGROUND: Little is known about the role of low physical activity at work (sedentary work or low physical job demand) in the increasing prevalence of obesity of US workers. METHODS: This cross-sectional and secondary data analysis included 1,001 male and 1,018 female workers (age range: 32-69) from the National Survey of Midlife Development in the United States (MIDUS) II study (2004-2006). Sedentary work and physical job demand were measured by questionnaire items. Total obesity (based on body mass index) and central obesity (based on waist circumference) were defined using WHO criteria. RESULTS: After controlling for covariates (socio-demographic, psychosocial working conditions, health status, and health behaviors), sedentary work, low physical job demand, or their combination increased the risk for total and central obesity in male workers, particularly when they worked longer than 40 hr per week. Sedentary work marginally increased the risk for total and central obesity in female workers. CONCLUSIONS: Low physical activity at work is a significant risk factor for total and central obesity in middle-aged US male workers.

Elevated blood pressure, decreased heart rate variability and incomplete blood pressure recovery after a 12-hour night shift work.

Shift work has been associated with increased risk of cardiovascular disease. This study was designed to determine the hemodynamic effects of 12-hour (12-h) shifts, and changes in blood pressure (BP) and heart rate variability (HRV) during 36 h rest time following 12-h shifts. Fifteen male shift workers with a mean age of 32.9 yr were recruited from a semiconductor factory. Ambulatory BP (AmBP) monitoring was performed for a total of 48 h for each participant. Six workers were monitored for 48 h by Holter electrocardiogram on both the day and night shifts. Paired self-comparison was used to estimate the difference between two hourly measurements of 12-h BP, HR, and HRV using the same timetable intra-individually. We also applied mixed models to estimate the effects of 12-h shifts on the delayed recovery of BP and heart rate (HR) in six workers who completed 96-h AmBP monitoring, including a 48-h night shift-rest period and another day shift period. Results showed that 12-h night shift work gave a persistently elevated systolic and diastolic BP (SBP and DBP) and HR, and decreased HRV compared to 12-h day shift work with the corresponding resting time. In addition, there was delayed SBP and DBP recovery on the first 12-h rest time in night shift workers, which was further demonstrated on the second 12-h rest time after adjustment for possible confounders through mixed models. In conclusion, 12-h night shift work may elevate BP and HR and decrease HRV. It is also associated with delayed BP recovery.

Work hours and self-reported hypertension among working people in California.

Among the risk factors for hypertension, stress, especially work stress, has drawn increasing attention. Another potential work-related risk factor for hypertension identified in the past few years is work hours. This article presents an analysis of work hours and self-reported hypertension among the working population in the state of California. The data set used for this study comes from the Public Use File of the 2001 California Health Interview Survey. The logistic regression analysis shows a positive association between hours worked per week and likelihood of having self-reported hypertension. Compared with those working between 11 and 39 hours per week, individuals working 40 hours per week were 14% (95% CI: 1.01 to 1.28) more likely to report hypertension, those who worked between 41 and 50 hours per week were 17% (95% CI: 1.04 to 1.33) more likely to report hypertension, and those who worked >or=51 hours per week were 29% (95% CI: 1.10 to 1.52) more likely to report hypertension after controlling for various potentially confounding variables, including demographic and biological risk factors and socioeconomic status. This analysis provides evidence of a positive association between work hours and hypertension in the California working population.

Is job strain a major source of cardiovascular disease risk?

Empirical studies on job strain and cardiovascular disease (CVD), their internal validity, and the likely direction of biases were examined. The 17 longitudinal studies had the highest validity ratings. In all but two, biases towards the null dominated. Eight, including several of the largest, showed significant positive results; three had positive, nonsignificant findings. Six of nine case-control studies had significant positive findings; recall bias leading to overestimation appears to be fairly minimal. Four of eight cross-sectional studies had significant positive results. Men showed strong, consistent evidence of an association between exposure to job strain and CVD. The data of the women were more sparse and less consistent, but, as for the men, most of the studies probably underestimated existing effects. Other elements of causal inference, particularly biological plausibility, corroborated that job strain is a major CVD risk factor. Additional intervention studies are needed to examine the impact of ameliorating job strain upon CVD-related outcomes.

Life-course exposure to job strain and ambulatory blood pressure in men.

This 1985-1995 study was designed to assess the association between blood pressure (measured by using an ambulatory monitor) and history of exposure to job strain. Items from the Job Content Questionnaire were completed by 213 employed men, aged 30-60 years at entry into the Work Site Blood Pressure Study in New York City, New York, for each previous job they had held. The systolic blood pressure of men employed for >/=25 years who were exposed to job strain for 50% of their work life was 4.8 mmHg (95% confidence interval: -3.7, 13.4) higher at work and 7.9 mmHg (95% confidence interval: 0.8, 15.0) higher at home than that of men with no past exposure, independent of current exposure. Evidence was inconsistent for the hypothesis of rapid induction of/recovery from the effects of job strain on blood pressure, and there was little effect of past job strain on diastolic blood pressure. These findings provide some support for the hypothesis of an effect of cumulative burden of exposure to job strain on systolic blood pressure.

Lower socioeconomic status among men in relation to the association between job strain and blood pressure.

OBJECTIVES: This study attempted to determine whether the association between job strain (high job demands plus low job control) and blood pressure among men varies by socioeconomic status. METHODS: The cross-sectional associations between job strain and ambulatory blood pressure, by level of education, occupational status, and income, and the interaction between job strain and these measures of socioeconomic status were assessed by multiple linear regression, adjusted for age, race or ethnicity, body mass index, alcohol use, smoking, standing position, and worksite for 283 men, aged 30-60 years, from eight worksites in New York City. RESULTS: A substantial association between job strain and work ambulatory blood pressure was found among men with lower socioeconomic status, ranging from 2.7-11.8 mm Hg systolic to 1.9-6.1 mm Hg diastolic blood pressure, depending upon the measure of socioeconomic status examined. However, in the groups with high socioeconomic status, the association between job strain and ambulatory blood pressure at work was much smaller, the range in blood pressure being 0-5.3 (systolic) and 0.2-2.1 (diastolic) mm Hg. Two of the 10 tests of the interaction between job strain and socioeconomic status had a P-value of <0.05. CONCLUSIONS: These data provide evidence that the relationship between job strain and blood pressure is greater among men with lower socioeconomic status.

Validity and reliability of a work history questionnaire derived from the Job Content Questionnaire.

Job design risk factors for hypertension and heart disease have often been assessed by the Job Content Questionnaire (JCQ). Job characteristics are typically assessed only once, however, which can result in misclassification and bias results toward the null. Newer approaches, which assess job characteristics over a working life, are hampered by the need to ask numerous questions about each job, increasing survey length and potentially reducing response rates. Participants in the Work Site Blood Pressure Study, a prospective study of psychosocial factors and ambulatory blood pressure, completed the JCQ about their current jobs. At later dates, 213 employed men, a subset of the original cohort, retrospectively completed the Work History Questionnaire (WHQ), a short version of the JCQ, for each past job. The WHQ exhibited moderate validity for assessing past job characteristics, a weak association with systolic blood pressure, and expected patterns of change over time. Thus, it may be a valuable tool for measuring the health effects of historical job characteristics, which often change over time.

Work stressors and cardiovascular disease.

Over the past 20 years, an extensive body of research evidence has documented that psychosocial work stressors are risk factors for hypertension and cardiovascular disease. These stressors, which appear to be increasing in prevalence, include job strain (the combination of psychological job demands and low job control), imbalance between job efforts and rewards, threat-avoidant vigilant work, and long work hours. This article reviews the evidence linking these stressors with hypertension and CVD, and the physiological and social psychological mechanisms underlying the associations. Also described are methods for measuring work stressors and new, more accurate techniques for measuring blood pressure. Finally, strategies for reducing work stressors and preventing hypertension and CVD are reviewed. These include clinical assessment, worksite health promotion, work organization interventions, legal approaches and work site surveillance.

Body fat and fat distribution in relation to sex differences in blood pressure.

The extent to which the relationship between body fat and blood pressure either differs by sex or explains sex differences in blood pressure is examined. Estimates of the relationship of blood pressure to several measures of adiposity in men and women were obtained from a systematic review of the literature and tests of whether these relationships differ by sex were performed. Analysis of covariance (controlling for age and race) was used for both casual and ambulatory blood pressure in the Cornell Worksite Blood Pressure Study (N = 276). In general, most adiposity measures were significantly related to casual and ambulatory blood pressure in men and women. Subscapular skinfold thickness and body mass index exhibited the strongest associations. The vast majority of adiposity/blood pressure associations were not significantly different for men and women. Finally, sex differences in adiposity did not account for much of the sex difference observed in blood pressure. © 1995 Wiley-Liss, Inc.