The relationship between physical activity, sleep duration and depressive symptoms in older adults: The English Longitudinal Study of Ageing (ELSA)

Research to date suggests that physical activity (PA) is associated with distinct aspects of sleep, but studies have predominantly focused on sleep quality, been carried out in younger adults, and have not accounted for many covariates. Of particular interest is also the reported relationship between physical activity and depression in older adults and as such, their associations with sleep duration. Here we examine the cross-sectional relation between physical activity and sleep duration in a community-dwelling sample of 5265 older adults from the English Longitudinal Study of Ageing. We analysed the data using multiple regression, with physical activity as a categorical exposure and sleep duration a continuous outcome, as well as testing the interaction between physical activity and depressive symptoms, which was significant (p < 0.001). We therefore stratified our analyses by depressive symptomatology. Our main finding was that, in the group with elevated depressive symptoms only, physical activity was positively associated with sleep duration in models adjusted for all covariates (age, sex, wealth, ethnicity, smoking, alcohol consumption, BMI, long-standing illness) across low [B (mean difference in sleep duration) = 25.22 min, 95% CI = (3.72; 46.72)], moderate [B = 27.92 min, 95% CI = (6.59; 49.26)] and high [B = 31.65 min, 95% CI = (7.36; 55.94)] PA groups, in comparison to the sedentary group. However, we observed no relation between physical activity and sleep duration in respondents who reported no depressive symptoms, irrespective of physical activity level (p > 0.05). Our findings suggest that a potentially effective way of improving sleep in older adults with depressive symptoms is via physical activity interventions. Keywords: Ageing, Exercise, Depression, Epidemiology, Moderation, Sleep duratio