Background/Purpose: An estimated 21% of disability attributed to arthritis is related to inactivity. This study analyzed data from the Osteoarthritis Initiative (OAI) to evaluate the influence of increasing physical activity on change in disability in previously inactive community-dwelling adults with or at greater risk to develop symptomatic radiographic knee osteoarthritis (OA).

Methods: Physical activity was measured by uniaxial accelerometers at baseline and 2 years. All study participants were inactive at baseline. Baseline inactivity was identified by the absence of a single 10-minute session of moderate or vigorous (MV) activity in a week. At 2 years of follow-up, inactive persons were further classified into three groups according to the Federal physical activity guidelines: those who (1) increased MV activity to meet guidelines (at least 150 minutes/week MV activity acquired in sessions ≥10min), (2) insufficiently increased MV activity (≥ 1 session/week but below guidelines) or (3) remained inactive. Disability domains of daily activity limitation (DAL) and frequency (DAF) assessed by Late-Life Disability Instrument were also ascertained at baseline and two years. Multiple linear regression evaluated the associations of changes in physical activity status with change in DAL and DAF adjusting for socioeconomic factors, health factors, and baseline DAL or DAF scores.

Results: The study included 545 adults with age range of 49-83 years; 64% had radiographic knee OA, 68% had WOMAC pain in at least one knee. At 2 years, 28% improved physical activity status. Compared to baseline, adults who remained inactive on average had worse DAL and DAF (mean change: -1.15 DAL, -0.46 DAF); people who became insufficiently active improved their DAL (mean change: 1.95 DAL, -0.41 DAF); those who met guidelines improved both their DAL and DAF (mean change: 10.31 DAL, 2.68 DAF). There was a significant graded relationship between increased physical activity and improved disability scores in both DAL (trend p-value <0.001) and DAF (trend p-value = 0.027) after adjusting for covariates. 

Conclusion: These prospective data demonstrated increased physical activity was associated with reduced severity of disability over two years among previously inactive older adults. A significant graded relationship was found between improved physical activity status and decreased disability. While increasing physical activity to levels recommended by guidelines provided the most benefit, even increasing activity to below guideline levels was beneficial in reducing disability severity. These findings provide support for the encouragement of increasing activity to prevent worsening of disability. 

Table. Late Life Disability Limitation and Frequency Average 2-year Changes from Baseline: Compared to those who remained inactive, those who moved from inactivity to more activity had significantly improved disability severity (positive average change)

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/influence-of-increasing-physical-activity-on-longitudinal-changes-in-disability-status-among-inactive-older-adults/