To examine the 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 osteoarthritis (OA).
Using 48-month (baseline) accelerometry data from the Osteoarthritis Initiative, we classified participants as Active-Low Sedentary (≥ 1 10-min bout/week of MVPA, lowest tertile for standardized sedentary time), Active-High Sedentary (≥ 1 10-min bout/week of MVPA, top 2 tertiles for standardized sedentary time), Inactive-Low Sedentary (zero 10-min bouts/week of MVPA, lowest tertile for standardized sedentary time), and Inactive-High Sedentary (zero 10-minute bouts/week of MVPA, top 2 tertiles for standardized sedentary time) groups. Functional limitation was defined as > 12 seconds for the 5-repetition sit-to-stand test (5XSST) and < 1.22 m/s gait speed during the 20-meter walk test. To investigate the association of exposure groups with risk of developing functional limitation 4 years later, we calculated adjusted risk ratios (aRR; adjusted for potential confounders).
Of 1091 and 1133 participants without baseline functional limitation, based on the 5XSST and 20-meter walk test, respectively, 15% and 21% developed functional limitation 4 years later. The Inactive-Low Sedentary and Inactive-High Sedentary groups had increased risk of developing functional limitations compared to the Active-Low Sedentary and Active-High Sedentary groups. The Inactive-Low Sedentary group had 72% (aRR 1.72, 95% CI 1.00-2.94) and 52% (aRR 1.52, 95% CI 1.03-2.25) more risk of developing functional limitation based on the 5XSST and 20-meter walk test, respectively, compared to the Active-Low Sedentary group.
Regardless of sedentary category, being inactive (zero 10-min bouts/week in MVPA) may increase the risk of developing functional limitation in adults with knee OA.