Associations between number of sick-leave days and future all-cause and cause-specific mortality: a population-based cohort study

Background: As the number of studies on the future situation of sickness absentees still is very limited, we aimed to investigate the association between number of sick-leave days and future all-cause and cause-specific mortality among women and men. Methods: A cohort of 2 275 987 women and 2 393 248 men, aged 20-64 years in 1995 was followed 1996-2006 with regard to mortality. Data were obtained from linked authority-administered registers. The relative risks (RR) and 95% confidence intervals (CI) of mortality with and without a 2-year wash-out period were estimated by multivariate Poisson regression analyses. All analyses were stratified by sex, adjusting for socio demographics and inpatient care. Results: A gradually higher all-cause mortality risk occurred with increasing number of sick-leave days in 1995, among both women (RR 1.11; CI 1.07-1.15 for those with 1-15 sick-leave days to RR 2.45; CI 2.36-2.53 among those with 166-365 days) and men (RR 1.20; CI 1.17-1.24 to RR 1.91; CI 1.85-1.97). Multivariate risk estimates were comparable for the different causes of death (circulatory disease, cancer, and suicide). The two-year washout period had only a minor effect on the risk estimates. Conclusion: Even a low number of sick-leave days was associated with a higher risk for premature death in the following 11 years, also when adjusting for morbidity. This was the case for both women and men and also for cause-specific mortality. More knowledge is warranted on the mechanisms leading to higher mortality risks among sickness absentees, as sickness certification is a common measure in health care, and most sick leave is due to diagnoses you do not die from.