Musculoskeletal Impairments in the Norwegian Working Population: The Prognostic Role of Diagnoses and Socioeconomic Status A Prospective Study of Sickness Absence and Transition to Disability Pension

Study Design. Population-based, 5-year prospective cohort study. Objective. To assess the incidence of musculoskeletal disorders (MSDs) in sickness absence longer than 8 weeks in Norway, and to identify diagnostic and socioeconomic predictors of the transition to disability pension (DP). Summary of Background Data. MSDs are prevalent and of major concern for sickness absence. Previous epidemiological studies are largely cross-sectional and based on self-reports, often with low response rates, selection, and reporting bias. Prospective studies with physician-verified diagnoses might be a better approach. Methods. Thirty-seven thousand nine hundred forty-two females and 26,307 males with an episode of sickness absence > 8 weeks in 1997, certified with a MSD were followed up for 5 years. Diagnostic and sociodemographic data were obtained from a national database. Cases were divided into 9 diagnostic subgroups, based on the International Classification of Primary Health Care. Survival analysis was performed with granting of DP as the endpoint, in the full sample and for diagnostic subgroups. Results. Over all 20% of cases obtained DP during follow-up. Among those aged 50 to 62 and among those with only basic education 46% obtained DP. DP rates were highest for osteoarthrosis (47%), rheumatoid arthritis (46%), and myalgia/fibromyalgia (38%). Fractures/injuries had the lowest rate. Controlled for age, education and income, relative risk of DP was 1.5 (95% CI: 1.4-1.6) for upper limb problems, 2.0 (95% CI: 1.8-2.1) for back problems, 2.8 (95% CI: 2.5-3.1) for osteoarthrosis, 3.3 (95% CI: 3.0-3.6) for myalgia/fibromyalgia, and 4.2 (95% CI: 3.9-4.7) for rheumatoid arthritis, compared to "fractures and injuries." Conclusion. Age, diagnoses, and socioeconomic variables were important predictors of an adverse outcome among workers with a sickness absence of 8 or more weeks. Further research is needed to determine whether differentiated follow-up strategies might prevent permanent disability.