Couple synchrony in physical activity: Effects on individuals with knee osteoarthritis

Background Physical activity (PA) is crucial for managing osteoarthritis (OA) symptoms, but maintaining an active lifestyle remains challenging. Given the influence of spouses on each other's health behaviors, PA synchrony - the concurrent PA engagement between partners - may enhance PA levels and emotional well-being in individuals with knee osteoarthritis (IKOAs). Purpose We investigate whether daily PA synchrony in couples is associated with PA levels and emotional well-being in IKOAs. Methods We analyzed 22 days of actigraphy data from 140 couples, each with 1 partner with knee OA (IKOAs: age 50-92, M = 65.3; 42% male). PA synchrony was operationalized as the association between partners' PA levels measured concurrently within each 1-hour time window throughout the day. Using multilevel structural equation modeling, synchrony was estimated and decomposed into 2 components: day level (capturing daily fluctuations) and couple level (reflecting overall average synchrony). Associations between synchrony at each level and IKOAs' PA and emotional well-being were examined. We accounted for shared diurnal rhythms in PA, a potential source of spurious synchrony, to enhance the precision of synchrony estimates. Results While couples generally showed synchronized PA, there were significant day-to-day fluctuations. On days when couples exhibited higher-than-usual PA synchrony, IKOAs engaged in significantly more PA. Regarding emotional well-being, increased daily synchrony was associated with higher positive and lower negative affect. Conclusions Findings highlight the importance of separating short-term fluctuations from stable couple dynamics. Findings suggest that promoting short-term synchronized PA between partners may improve both PA and emotional well-being in IKOAs. Our analytic framework is broadly applicable to couple-based research on shared health behaviors.