The relationship between restless sleep and symptoms of the knee: data from the Osteoarthritis Initiative

Objective To examine the associations between restless sleep and knee symptoms among individuals with radiographically confirmed KOA. Methods Cross-sectional and longitudinal associations were examined using Osteoarthritis Initiative (OAI) data. Participants with radiographic KOA ( n = 2517) were asked how often sleep was restless in the past week over the 4 years, and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) was used to measure knee symptoms. Adjusted β coefficients (aβ) and 95% confidence intervals (CI) were derived from generalized estimating equations (GEEs) models stratified by sex. Results One in 7 participants reported ≥ 3 nights with restless sleep. Cross-sectional analyses indicated that restless sleep 5–7 nights was associated with worse symptoms (Women: pain: aβ 1.93, 95% CI 1.12–2.74, stiffness: aβ 0.57, 95% CI 0.19–0.94, physical function: aβ 5.68, 95% CI 3.09-8.27; Men: pain: aβ = 1.85, 95% CI 0.85–2.86; stiffness: aβ 0.63, 95% CI 0.15–1.12; physical function: aβ 5.89, 95% CI 2.68–9.09) compared with < 1 night. Longitudinal analyses confirmed that more nights with restless sleep were associated with worse pain ( P trend = 0.01) and function ( P trend = 0.04) in women and physical function in men ( P trend = 0.04), although estimates did not meet thresholds for minimal clinically meaningful differences. Conclusion While the analysis of cross-sectional data supported the association between restless sleep and KOA symptoms, such relationships were not confirmed in more robust longitudinal analysis. Further research examining whether sleep quality, duration, or disorders is associated with worsening symptoms in persons with KOA is warranted. Key Points • The prevalence of frequent restless sleep among persons with knee OA is not uncommon. • There were linear trends between frequency of restless sleep and self-reported symptoms of the knee in cross-sectional analyses. • In the more robust longitudinal analysis, despite the statistically significant linear trends observed between frequency of restless sleep and symptoms (women: pain and physical function; men: function), none appeared to reach the a priori selected ranges for minimally clinically relevant differences.