Daily walking and the risk of incident functional limitation in knee OA: An observational study.
Arthritis care & research. 2014;66(9):1328-1336.
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Background: Physical activity is recommended to mitigate functional limitations associated with knee osteoarthritis (OA). However, it is unclear whether walking on its own protects against the development of functional limitation. Methods: Walking over 7 days was objectively measured as steps/day within a cohort of people with or at risk of knee OA from the Multicenter Osteoarthritis Study. Incident functional limitation over two years was defined by performance-based (gait speed â‰¤ 1.0 m/s) and self-report (WOMAC physical function â‰¥ 28/68) measures. We evaluated the association of steps/day at baseline with developing functional limitation two years later by calculating risk ratios adjusted for potential confounders. The number of steps/day that best distinguished risk for developing functional limitation was estimated from the maximum distance from chance on Receiver Operator Characteristic curves. Results: Among 1788 participants (mean age 67, mean BMI 31 kg/m(2) , female 60%), each additional 1000 steps/day was associated with a 16% and 18% reduction in incident functional limitation by performance-based and self-report measures, respectively. Walking < 6000 and < 5900 steps/day were the best thresholds to distinguish incident functional limitation by performance-based (67.3%/71.8% [sensitivity/specificity]) and self-report (58.7%/68.9%) measures, respectively. Conclusions: More walking was associated with less risk of functional limitation over two years. Walking â‰¥ 6000 steps/day provides a preliminary estimate of the level of walking activity to protect against developing functional limitation in people with or at risk of knee OA. Â© 2014 American College of Rheumatology.