Joint association of moderate-to-vigorous intensity physical activity and sedentary behavior with incident functional limitation: data from the Osteoarthritis Initiative (OAI)

OBJECTIVE To examine joint association of moderate-to-vigorous intensity physical activity (MVPA) and sedentary behavior with the risk of developing functional limitation 4 years later in adults with knee OA. METHODS Using 48-month (baseline) accelerometry data from Osteoarthritis Initiative, , we classified participants as Active-Low Sedentary (≥1 10-minute bout/week of MVPA, lowest tertile for standardized sedentary time), Active-High Sedentary (≥1 10-minute bout/week of MVPA, top two tertiles for standardized sedentary time), Inactive-Low Sedentary (0 10-minute bout/week of MVPA, lowest tertile for standardized sedentary time) and Inactive-High Sedentary (0 10-minute bout/week of MVPA, top two tertiles for standardized sedentary time) groups. Functional limitation was defined as >12sec for five repetition sit-to-stand test (5XSST) and <1.22m/sec gait speed during 20-meter walk test. To investigate the association of exposure groups with risk of developing functional limitation 4 years later, we calculated risk ratios(aRR) adjusted for potential confounders. RESULTS Of 1,091 and 1,133 participants without baseline functional limitation, based on 5XSST and 20-meter walk test, respectively, 15% and 21% developed functional limitation 4 years later. Active- High Sedentary group didn't have, while Inactive-Low Sedentary, and Inactive-High Sedentary groups had increased risk of developing functional limitations compared to Active-Low Sedentary group. Inactive-Low Sedentary group had 72% (aRR[95% confidence interval]1.72[1.00, 2.94]) and 52% (1.52[1.03, 2.25]) more risk of developing functional limitation based on 5XSST and 20-meter walk test, respectively, compared to Active-Low Sedentary group. CONCLUSION Regardless of sedentary category, being inactive (0 10-minute bouts/week in MVPA) may increase risk of developing functional limitation in adults with knee OA.