Do work-related mechanical and psychosocial factors contribute to the social gradient in long-term sick leave: a prospective study of the general working population in Norway.

AIMS: A social gradient in long-term sick leave (LTSL) rates is well established, but only a few studies have examined to what extent this gradient may be explained by mechanical and psychosocial work environment factors.
METHODS: A randomly drawn cohort from the general population in Norway, aged 18-69 years, was interviewed in the second half of 2009 (n=12,255, response at baseline 60.9%) and followed up in national registries to the end of 2010. Eligible respondents were registered with an active employee relationship of at least 100 actual working days in 2009 and 2010 (n=6758). Based on administrative register data, respondents were coded into five educational levels (university/college ≥4 years was set as the reference group). Eight work-related psychosocial factors and 10 mechanical exposures were measured. The outcome of interest was medically confirmed LTSL ≥40 working days during 2010.
RESULTS: In total, 9.4% (635 individuals) were classified with LTSL during 2010. There was a strong social gradient ranging from 12.4% (elementary) to 3.3% (university/college ≥4 years) among men. The corresponding figures among women were 15.4 and 4.6%. Adjusting for work-related mechanical and psychosocial factors explained between 41 and 44% of the social gradient in men. Among women, the corresponding figures were 31 and 54%.
CONCLUSIONS: Work-related mechanical and psychosocial factors contribute to the social gradient in LTSL. The work-related factors that accounted for this gradient were rather similar for men and women.