Physical activity changes associated with functional transitions in adults aged 50 and older

Researchers analyzed longitudinal data from five population-based aging cohorts to assess whether changes in physical activity were associated with transitions among independent status, instrumental activities of daily living (IADL) disability, and basic activities of daily living (BADL) disability. Of 266,204 participants aged 50 years or older, 112,855 were included in the primary complete-case analysis. Cohort-specific estimates from continuous-time three-state Markov models were combined using random-effects meta-analysis.

Compared with remaining inactive, becoming active was associated with a lower transition intensity from independence to IADL disability (HR 0.58; 95% CI 0.46–0.72) and a higher recovery intensity from BADL disability to independence (HR 1.73; 95% CI 1.40–2.13). Becoming inactive, compared with remaining active, was associated with the reverse pattern: HRs were 1.28 (95% CI 1.03–1.58) for deterioration and 0.66 (95% CI 0.61–0.72) for recovery. Multiple-imputation findings were directionally similar.

The findings suggest an association between activity patterns and functional transitions, but do not establish that changes in activity caused those outcomes. Between-cohort variation was substantial (I² 26.1%–98.5%), and 12 of 18 prediction intervals included 1. Death was not modeled as an outcome state; follow-up ended at the last valid functional assessment.