Overtime work and incident coronary heart disease: the Whitehall II prospective cohort study.

AIMS To examine the association between overtime work and incident coronary heart disease (CHD) among middle-aged employees. METHODS AND RESULTS Six thousand and fourteen British civil servants (4262 men and 1752 women), aged 39-61 years who were free from CHD and worked full time at baseline (1991-1994), were followed until 2002-2004, an average of 11 years. The outcome measure was incident fatal CHD, clinically verified incident non-fatal myocardial infarction (MI), or definite angina (a total of 369 events). Cox proportional hazard models adjusted for sociodemographic characteristics showed that 3-4 h overtime work per day was associated with 1.60-fold (95% CI 1.15-2.23) increased risk of incident CHD compared with employees with no overtime work. Adjustment for all 21 cardiovascular risk factors measured made little difference to these estimates (HR 1.56, 95% CI 1.11-2.19). This association was replicated in multivariate analysis with only fatal cardiovascular disease and incident non-fatal MI as the outcome (HR 1.67, 95% CI 1.02-2.76). CONCLUSION Overtime work is related to increased risk of incident CHD independently of conventional risk factors. These findings suggest that overtime work adversely affects coronary health.