Physical Activity Predicts Higher Physical Function in Older Adults: The Osteoarthritis Initiative

Objectives: Physical activity reduces mobility impairments in elders. We examined the association of physical activity on risk of subjective and objective physical function in adults with and at risk for osteoarthritis (OA). Methods: Adults aged >= 60 years from the longitudinal Osteoarthritis Initiative, a prospective observational study of knee OA, were classified by sex-specific quartiles of Physical Activity Score for the Elderly scores. Using linear mixed models, we assessed 6-year data on self-reported health, gait speed, Late-Life Function and Disability Index (LLFDI) and chair stand. Results: Of 2252 subjects, mean age ranged from 66 to 70 years. Within each quartile, physical component (PCS) of the Short Form-12 and gait speed decreased from baseline to follow-up in both sexes (all P < .001), yet the overall changes across PASE quartiles between these 2 time points were no different (P = .40 and .69, males and females, respectively). Decline in PCS occurred in the younger age group, but rates of change between quartiles over time were no different in any outcomes in either sex. LLFDI.scores declined in the 70+ age group. Adjusting for knee extensor strength reduced the strength of association. Conclusions: Higher physical activity is associated with maintained physical function and is mediated by muscle strength, highlighting the importance of encouraging physical activity in older adults with and at risk for OA.