Cumulative physical workload and mobility limitations in middle-aged men and women: a population-based study with retrospective assessment of workload

PURPOSE: To assess the association between exposure to physical workload throughout working life and risk of mobility limitations in midlife in a population-based Danish cohort. METHODS: The study was cross-sectional with a retrospective exposure assessment, and data were from a questionnaire used in the Copenhagen Aging and Biobank. Cumulative physical workload was estimated by combining information about the participants’ employments and data from a job exposure matrix. Daily amount of lifting was standardised in ton-years (lifting 1000 kg/day/year) and grouped in 5 exposure groups (no/minor (1–2 ton-years)/low (3–10 ton-years)/moderate (11–20 ton-years)/high exposure (> 20 ton-years)). The outcome was self-reports of mobility limitations (running 100 m, walking 400 m, and climbing stairs to the 2nd floor) in midlife. The association between exposure and outcome was analysed using logistic regression models. RESULTS: We included 4996 men and 2247 women, mean age 56 years. 21% of men and 10% of women were in the highest exposure-group (> 20 ton-years). Higher cumulative exposure was associated with higher odds for mobility limitations. Exposure to more than 20 ton-years compared to no exposure increased the odds for limitations in walking, age-adjusted odds ratio (OR) 3.2 (95% CI: 2.4–4.3) for men, 2.3 (1.4–3.8) for women. Corresponding results for running: 2.5 (2.2–3.0) for men, 1.6 (1.2–2.2) for women, and for limitations in climbing stairs: 4.2 (3.3–5.2) for men, 1.7 (1.2–2.4) for women. Results were attenuated when confounders were added. CONCLUSIONS: Exposure to physical workload throughout working life is associated with higher odds for mobility limitations in midlife.