Objective: The purpose of this prospective cohort study with 1-year follow-up was to determine prognostic factors for duration of sickness absence due to musculoskeletal disorders.
Methods: Workers were included when on sickness absence of 2 to 6 weeks due to musculoskeletal disorders. A self-administered questionnaire was used to collect personal and work-related factors, pain, functional disability, and general health perceptions. Statistical analysis was done with Cox proportional hazard regression with an interaction variable with time for every risk factor of interest. Univariate and multivariate analyses were performed on musculoskeletal disorders and, separately, for low back pain.
Results: The main factors that were associated with longer sickness absence were older age, gender, perceived physical workload, and poorer general health for neck, shoulder and upper extremity disorders, and functional disability, sciatica, worker's own perception of the ability of return to work, and chronic complaints for low back pain. Workers with a high perceived physical work load returned to work increasingly slower over time than expected, whereas workers with a high functional disability returned to work increasingly faster over time.
Conclusions: High pain intensity is a major prognostic factor for duration of sickness absence, especially in low back pain. The different disease-specific risk profiles for prolonged sickness absence indicate that low back pain and upper extremity disorders need different approaches when applying intervention strategies with the aim of early return to work. The interaction of perceived physical workload with time suggests that perceived physical workload would increasingly hamper return to work and, hence, supports the need for workplace interventions among workers off work for prolonged periods.