Occupational physical activity and the development of impaired mobility: The 12-year follow-up of the Baltimore epidemiologic catchment area sample

Objective: To examine the association between occupational physical activity and self-reported disability. Design: Population-based case control analysis of a longitudinal population-based study in east Baltimore. Eligible participants were aged 18 to 29 yr in 1981, had complete information on occupation in 1981, no disability with tasks related to the domain of mobility in 1981, and complete information on mobility function in 1993 (n = 174). Occupations were divided into low, moderate, and high metabolic equivalents based on job category in 1981. The main outcome measure was disability defined by self-report of difficulty in one or more of five exercise mobility tasks in 1993. Results: Of 174 eligible participants, 45 (26%) reported the onset of disability at follow-up in 1993. A crude odds ratio of 0.25 (95% confidence interval, 0.06, 0.82) was found for the association of moderate compared with low occupational physical activity and the risk of incident disability in mobility tasks. After adjustments to control for possible confounders, moderate job metabolic activity (1.8-2.9 Mets) was independently protective against disability in this cohort (odds ratio = 0.25; 95% confidence interval = 0.083, 0.783). Conclusion: In this cohort of people aged 18 to 29 yr, a moderate amount of occupational physical activity was protective against disability in mobility tasks.