Sleep as an effect modifier for physical activity intervention efficacy: secondary analysis of data from two randomized controlled trials

Background : Regular physical activity (PA) improves health across various domains, reducing the risk of cardiovascular disease and certain forms of cancer while improving mental health. Latinas have high rates of inactivity and are disproportionately burdened by health conditions associated with regular PA. Thus, research is needed to elucidate determinants of success in PA interventions in this population. Sleep is a health behavior that has an established bidirectional relationship to PA, yet it remains unclear how sleep may moderate PA intervention efficacy. Purpose : This study examines sleep as a moderator of the intervention effect on PA outcomes in two randomized controlled trials among sedentary Latinas. Methods : Using a series of generalized mixed effects models with subject-specific intercepts, we tested whether nighttime sleep duration moderated intervention effects on PA outcomes. Analyses were run separately on data from two studies to help establish consistency of findings across two similar participant populations. Results : Results indicated that nighttime sleep duration (whether operationalized continuously or dichotomously based on guidelines) was a significant moderator of intervention effects on PA outcomes over time, p’s<.05. Across studies, women who reported more nightly sleep, showed greater benefits from intervention vs. control (in Study 1) and enhanced vs. original intervention (in Study 2). Conclusions : To our knowledge, this is the first study to examine sleep as an effect modifier of PA intervention success. Findings suggest that sufficient sleep allows Latinas to benefit more from PA interventions and also additional points of contact and features.