Sleep Efficiency Moderates the Next-day Association between Physical Activity and Pain Intensity among Adults with Knee Osteoarthritis

Abstract

Previous studies have suggested that characteristics of sleep may modulate the physical activity-pain intensity association. This study aimed to identify which sleep parameters, if any, modify the next-day physical activity-pain intensity association in adults with knee osteoarthritis. This secondary analysis used data from people with knee osteoarthritis recruited to a pacing intervention trial. Up to seven days of pre-randomization actigraphy and pain intensity ecological momentary assessments (11-point numeric rating scale, administered five times/day at quasi-random intervals) were analyzed. Separate multi-level models with average pain intensity for that day as the outcome included interaction terms between previous night's sleep variables (efficiency, onset latency, time spent awake after sleep onset, and duration) and that day's daytime physical activity variables (person-centered; total activity count, maximum activity count, and average activity count/min). Models were adjusted for age, sex, and the individual's average pain intensity over the duration of the study. In the findings, 116 participants provided 799 days of data. Mean age was 64.9 (SD 8.0), 60% were female and 87% white. At baseline, 54% could be characterized as poor sleepers, determined by scoring >5 on the Pittsburgh Sleep Quality Index. Although higher person-centered average daily physical activity count (i.e., compared to the participant's study average) was associated with lower same-day average pain intensity, significant interaction was identified between previous night's sleep efficiency and person-centered average daily physical activity (p=0.03). After nights of higher sleep efficiency, there was a stronger negative association between within-day average physical activity and pain intensity. Findings indicate that optimizing sleep efficiency may be important to maximize the pain-relieving effects of physical activity in people with knee osteoarthritis. Future studies are required to replicate these findings and to investigate other features of sleep that may be salient in the physical activity-pain association. This secondary analysis used data collected for a project supported by the Rehabilitation and Research Branch of the Veterans Affairs Office of Research Development, grant number 1I01RX000410.