Background: There has been an increasing interest in the health effects of long working hours, but little empirical evidence to substantiate early case series suggesting an increased mortality risk. The aim of the current study is to quantify the mortality risk associated with long working hours and to see if this varies by employment relations and conditions of occupation.
Methods: A census-based longitudinal study of 414 949 people aged 20-59/64 years, working at least 35 h/week, subdivided into four occupational classes (managerial/professional, intermediate, own account workers, workers in routine occupations) with linkage to deaths records over the following 8.7 years. Cox proportional hazards models were used to examine all-cause and cause-specific mortality risk.
Results: Overall 9.4% of the cohort worked 55 or more h/week, but this proportion was greater in the senior management and professional occupations and in those who were self-employed. Analysis of 4447 male and 1143 female deaths showed that hours worked were associated with an increased risk of all-cause mortality only for men working for more than 55 or more h/week in routine/semi-routine occupations [adjusted hazard ratios (adjHR) 1.31: 95% confidence interval (CI) 1.11, 1.55] compared with their peers working 35-40 h/week. Their equivalent risk of death from cardiovascular disease was (adjHR 1.49: 95% CI 1.10, 2.00).
Conclusions: These findings substantiate and add to the earlier studies indicating the deleterious impact of long working hours but also suggest that the effects are moderated by employment relations or conditions of occupation. The policy implications of these findings are discussed.
Keywords: Hours worked; longitudinal study; mortality.