The role of familial factors in the associations between sickness absence and disability pension or mortality.

BACKGROUND Little is known about the factors influencing the future situation of individuals on sickness absence (SA) or disability pension (DP). The aim was to investigate whether being sickness absent is associated with future DP and premature death, and whether such associations can be explained by familial factors. METHODS A sample of 45 734 Swedish twins was followed for 13 years. Cox proportional hazard models were applied to analyse the associations between having a new SA spell/being granted DP in 1995 and DP/mortality during follow-up 1996-2008. The familial confounding was tested by studying twins that were different in their exposure to SA and DP, respectively, during 1995. RESULTS SA strongly predicted DP during a follow-up of 13 years, in both women [hazard ratios (HR) 3.03, 95% confidence intervals (CI) 2.82-3.25] and men (HR 3.83, 95% CI 3.50-4.18). A minor part of the associations seemed to be explained by familial factors. Both SA and DP increased risk for mortality. For SA, HR was 1.46 (1.27-1.69) for women and 1.31 (1.14-1.51) for men. For DP, HR was 1.38 (0.92-2.05) for women and 1.73 (1.24-2.42) for men; results suggested a small influence of familial factors. CONCLUSION SA was found to be a long-term risk factor for DP and premature death, in both women and men. Familial factors played no or a minor role for these associations. Being granted DP in 1995 also increased risk for premature death, with a slight indication of familial influences in both sexes.