Socio-economic differences in the association between sickness absence and mortality: the prospective DREAM study of Danish private sector employees.

OBJECTIVES: To examine duration of sickness absence as a risk marker for future mortality by socio-economic position among all private sector employees in Denmark in 1998-2004.
METHODS: All residents in Denmark employed in the private sector receiving sickness absence compensation in 1998 were investigated in a prospective cohort study. 236 207 persons (38.2% women, 61.8% men, age range 18-65, mean age 37.8 years) alive on 1 January 2001 were included in the study. Mortality from 1 January 2001 to 31 December 2004 was assessed using national register data. Deaths in 1999 and 2000 were excluded to determine the status of sickness absence duration as an early risk marker. For analyses within occupational grades, data were available for a sub-population of 137 607 study participants.
RESULTS: 3040 persons died during follow-up. The age-adjusted risk of future mortality increased by duration of sickness absence in a graded fashion among men and non-blue collar workers. Among women and blue collar workers, there was no association of mortality with duration of sickness absences below 6 weeks. However, employees with > or =6 weeks of absence compared to those with 1-week absence had a substantial excess risk of death in all groups: adjusted hazard ratio 2.2 (95% CI 1.8 to 2.7) for women, 2.1 (95% CI 1.8 to 2.4) for men, 3.7 (95% CI 1.9 to 7.2) in white collar occupations, 3.3 (95% CI 2.2 to 5.0) in intermediate grade occupations and 2.0 (95% CI 1.7 to 2.3) in blue collar occupations.
CONCLUSION: Administratively collected data on sickness absence compensation for periods > or =6 weeks identified "at risk" groups for future excess mortality in male and female private sector employees across occupational grade levels.