Association Between Depressive Symptoms and Self-Reported Physical Activity in Persons With Knee Osteoarthritis.

Objective: Depressive symptoms are common in patients with knee osteoarthritis (KOA) and reduce energy, motivation, and movement; thus, declines in physical activity (PA) could worsen as clinical disease progresses. The objective was to evaluate the longitudinal relationship between depressive symptoms and self-reported PA over time among persons with KOA.

Methods: The sample included Osteoarthritis Initiative participants (N = 2602) with radiographic disease (Kellgren-Lawrence grade ≥ 2). Depressive symptoms were measured using the Center for Epidemiologic Studies Depression Scale (CES-D; score ≥ 16) at baseline and first 3 follow-up visits. Self-reported PA was assessed with the Physical Activity Scale for the Elderly (PASE) at the first 4 follow-up visits. Marginal structural models controlling for time-invariant and time-varying confounders evaluated the longitudinal relationship between depressive symptoms and PASE z scores.

Results: Depressive symptoms were associated with lower PA (β -0.09; 95% CI -0.20 to 0.01) over time, but the relationship was not statistically significant. When including depressive symptoms-by-time interactions, the relationship was nonlinear from the first to fourth follow-up visit: visit 1 = -0.18 (95% CI -0.33 to -0.02), visit 2 = -0.05 (95% CI -0.22 to 0.11), visit 3 = -0.01 (95% CI -0.19 to 0.16), and visit 4 = -0.11 (95% CI -0.29 to 0.08). However, the interaction terms were not statistically significant.

Conclusion: Depressive symptoms may contribute to worse self-reported PA levels in persons with KOA. Future research should determine whether lower physical function is a further sequela of decreased PA related to depressive symptoms.