Shift work and mortality

Despite results linking shift work with ill health, only a few studies have addressed its relation with mortality. The purpose of the present study was to examine the hypothesis that shift work is a predictor of mortality. The study involved a sample of 22,411 individuals of the Swedish population. Data were obtained through annual phone interviews done between 1979 and 2000. Cox regression analysis was used to assess the association between shift work/day work as the independent variable and death/survival during the subsequent years as the dependent variable. Separate analyses were carried out for female and male white- and blue-collar workers, respectively. The results were adjusted for age, stress, physical work load, disease at the outset of the study, and smoking. Mortality was significantly increased for female white-collar workers, with a Hazard Ratio of 2.61 and a 95% confidence interval of 1.26-5.41. No other significant effects were found. It is concluded that blue-collar shift work is not related to mortality, but that risk of death is increased for women white-collar shift workers compared to women white-collar day workers.