Shift work and risk factors for cardiovascular disease: a study at age 45 years in the 1958 British birth cohort

This study examined associations between exposure to shift-work and risk factors for cardiovascular disease (CVD) and whether the associations are explained by socio-economic circumstances, occupational factors or health behaviours. Biological risk factors for CVD were measured in 7,839 participants of the 1958 British birth cohort at age 45 years who were in paid employment. Regular (a parts per thousand yen1/week) shift-workers included 46% working evenings (1800-2200), 28% weekends, 13% nights (2200-0400) and 14% early mornings (0400-0700). Adverse levels of several CVD risk factors were found in association with increasing participation in any shift-work. Men regularly working all four shift-work types had increased CVD risk factors of approximately 0.1-0.2 standard deviations (e.g. 0.8 kg/m(2) for body mass index; 1.2 cm for waist circumference) than those not regularly working shifts; for women, there was a positive linear trend for triglyceride levels, but a negative trend for diastolic blood pressure. Separate analyses of shift-work types showed associations primarily for night/morning working rather than evening/weekend working. Men had adverse levels of all CVD risk factors except blood pressure and total-cholesterol in association with night or early morning work and women had adverse triglyceride levels. Adjustment for socioeconomic, occupational factors and health behaviours explained most associations except for adiposity and C-reactive protein. Our results highlight night and early morning working associations with an adverse profile of CVD risk factors, which are partly explained by socioeconomic, other occupational factors and health behaviours.