Socioeconomic factors and disability retirement from back pain: a 1983-1993 population-based prospective study in Norway

STUDY DESIGN: A prospective observational study with an 11-year follow-up period was performed. OBJECTIVE: To investigate the influence of education and socioeconomic position on the incidence of permanent disability retirement from back pain. SUMMARY OF BACKGROUND DATA: Early retirement because of back pain is the extreme end point of a disabling process that is a great burden to the individual and costly for the society. Groups of employees at particular risk for permanent back pain disability need to be identified. METHODS: All employed men and women in Norway between the ages of 20 and 53 years in 1980 were included (n = 1,333,556). Outcome measures were disability retirement from inflammatory back pain (ICD-9 code 720) and noninflammatory back pain (ICD-9 codes 721 to 724). RESULTS: The 11-year cumulative incidence was 0.15% (n = 1990) for disability retirement from inflammatory back pain and 1. 64% (n = 21,829) for noninflammatory back pain and was somewhat higher in women than in men. Each year of formal education was independently associated with decreased risk for disability retirement from noninflammatory back pain (odds ratio OR] = 0.78; 95% confidence interval CI] = 0.77-0.79) and from inflammatory back pain (OR = 0.83; 95% CI = 0.81-0.86). Whereas disability from inflammatory back pain was moderately associated with socioeconomic status, there was a consistent upward trend in the association between disability retirement from noninflammatory back pain and lower socioeconomic position. The OR for unskilled workers was 3.1 (95% CI = 2.6-3.7) for men and 2.1 (95% CI = 1.7-2.5) for women, as compared with that of higher professionals. Stepwise analyses suggest that the effect of education is not mediated by socioeconomic status. CONCLUSIONS: The consistent upward trend in the relation of disability retirement to lower levels of education and socioeconomic position, even for inflammatory back pain, shows that factors related to the occupational and social environment play an important role in the disabling process. The stepwise, monotonic relation between socioeconomic position and disability retirement from back pain, even at the higher end of the socioeconomic scale, suggests that the relation between social class and back pain disability cannot be explained solely in terms of manual versus nonmanual jobs.