Change in physical workload and the risk of work disability due to musculoskeletal disorders: a register-based study of 1 703 935 workers in Sweden

Objective This register-based study examined whether changes over 14 years in occupational physical workload (PWL) affected the risk of registered work disability due to a musculoskeletal disorder (MSD). Methods This study included 1 703 935 workers in Sweden in 2005. PWL exposure was measured using job-exposure matrices linked to registered occupations in 1990 and 2005; change in PWL was defined between categories (low, medium, high) in either direction. The outcome was cumulative incidence of ‘work disability’ (either long-term sickness of at least 2 years or disability pension) due to MSD from 2006 to 2019. Crude and multivariate Cox proportional hazards regression models estimated sex-specific HRs with 95% CIs. Models were adjusted for sociodemographic factors and health and employment history. Results A total of 33 369 individuals (1.96%) became work disability cases during follow-up. Compared with workers with consistently high PWL, any reduction in PWL was associated with a decreased risk of work disability due to MSD (women: HR 0.57, 95% CI 0.52 to 0.63, men: HR 0.59, 95% CI 0.52 to 0.66 for change from high to low exposure). Compared with workers with consistently low PWL, any increase was associated with a higher risk of work disability due to MSD (women: HR 1.68, 95% CI 1.53 to 1.86, men: HR 2.19, 95% CI 1.89 to 2.52 for change from low to high). Conclusion In both sexes, decreases in PWL exposure were associated with a lower risk of MSD disability and increases in exposure with a higher risk.