Background/Purpose: Walking is the most common type of physical activity older adults employ for physical activity, which, when performed regularly, confers important health benefits.  When people develop knee osteoarthritis (OA), it is thought that they are likely to decrease the amount of walking they engage in due to pain and functional limitations. Whether this occurs in reality is not known. The impact of psychological health (e.g., depressive symptoms) on declines in walking activity in such individuals is also not known. The purpose of this study was to examine change in objectively measured walking activity over a 2-year period, and evaluate its relation to radiographic knee OA (ROA), knee pain, and psychological health.     

Methods: The Multicenter Osteoarthritis Study (MOST) is a NIH-funded longitudinal cohort of older adults who have or are at high risk of knee OA.  Steps/day over 7 days were objectively measured with a StepWatch monitor at 2 study visits, two years apart.  We calculated the absolute change in mean steps/day between visits.  We also evaluated mean change by categories of baseline disease status, i.e., ROA, frequent knee pain, or symptomatic knee OA (ROA + knee pain), and baseline psychological health status, i.e., presence of depressive symptoms and catastrophizing, using linear regression, adjusting for age, sex, and body mass index (BMI).

Results: Of the 1,318 subjects with the necessary data obtained (Age 66.9 ± 7.7, 59% women, BMI 30.6 ± 5.9), absolute steps/day declined significantly, albeit only slightly, from a mean of 9,173 steps/day at baseline to 9,004 steps/day 2-years later (i.e., 168 fewer steps ± 2,268, p = 0.007).  Those with depressive symptoms walked 927 ± 2,495 fewer steps/day 2-years later compared with 124 ± 2,959 fewer for people without depressive symptoms (p=0.007).  People with symptomatic knee OA walked 421 ± 3,100 fewer steps/day, which was not statistically significantly different than people without either ROA or frequent knee pain, who walked 517 ± 3,694 fewer steps/day 2-years later.  The other factors assessed were not statistically significantly associated with change in steps/day.

Conclusion:   Declines in walking activity over a 2-year period were minimal overall, and appeared to be more likely related to psychological health in people with or at high risk of knee OA rather than having painful knee OA itself.  Specifically, depressive symptoms were significantly associated with >900 fewer steps/day 2-years later, which is a clinically meaningful difference and beyond the 168 fewer steps/day due to aging.   Given the multiple benefits of physical activity, maintaining or improving steps/day in people with knee OA is important. Our findings support the notion that addressing psychological- rather than disease- and pain-factors is promising to minimize declines in daily walking in people with or at high risk of knee OA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/longitudinal-decline-in-stepsday-in-older-adults-with-or-at-high-risk-of-knee-oa/