O036 Sleep moderates but does not mediate aerobic benefits in osteoarthritis

Abstract Background Sleep quality is often impacted by osteoarthritis (OA) and may influence and/or explain the effects of aerobic exercise on pain and function. This study explores the role of sleep as a potential moderator and mediator of the effect of aerobic and resistance exercise compared to resistance exercise only in hip OA. Methods Exploratory analyses from 193 participants (mean [SD] age = 62.3 [6.9] years, 68% female) in a RCT comparing aerobic and resistance exercise to resistance exercise. Outcomes were change in hip pain severity (11-point numerical rating scale, higher scores indicate worse pain, minimal clinically important difference, MCID = 1.8]) and function (68-point Western Ontario and McMaster Osteoarthritis Index, higher scores indicate worse function, MCID = 6). The moderator (baseline) and mediator (3-month change) were the Pittsburgh Sleep Quality Index score (higher scores indicate worse sleep). Results Moderator analyses found those with poor sleep at baseline had greater improved function with aerobic exercise and resistance exercise compared to resistance exercise (0.81 (95% CI 0·09 to 1·53). The effect of aerobic and resistance exercise compared to resistance exercise on pain and function via change in sleep was a mean improvement of -0.08 [95% -0.24 to 0.08] and -0.61 [95% -1.67 to 0.51] points, respectively. Conclusion Sleep quality moderated the effects between exercise programs such that an additional small benefit in function may be conferred with aerobic and resistance exercise compared to resistance exercise in those with poor sleep. There was no evidence that effects between exercise programs were mediated by changes in sleep quality.