Regular physical activity and insomnia: An international perspective.

Both very low and very high levels of regular physical activity have been associated with degraded sleep quality. Cross-national variations in habitual physical activity levels, therefore, may contribute to cross-national differences in insomnia prevalence. The present study assesses and compares the extent to which weekly durations of moderate-intensity physical activity contribute to insomnia risk. Demographic, sleep, physical activity and general health profiles were obtained from a convenience sample of 9,238 adults drawn from five countries (South Africa, Australia, China, South Korea and the UK) using social media. Insomnia prevalence, using DSM-5 criteria, ranged from 4.1% (China) to 14.8% (UK). Evaluating risk using logistic regression adjusted only for age and gender, the lowest level of activity (<10 continuous min per week) was associated with significant insomnia risk (odds ratio = 1.37; 95% confidence interval = 1.05-1.79; p < 0.05). However, when adjusted for all covariates except country, only the highest level of physical activity (>300 min per week) was associated with significantly increased insomnia risk (odds ratio = 1.30; 95% confidence interval = 1.03-2.51; p < 0.05). Risk associated with high activity remained after the addition of "country" to the model (odds ratio = 1.31; 95% confidence interval = 1.02-1.69; p < 0.05). Across all models, female gender, low-rated health, low education and older age consistently increased insomnia risk. These cross-national data indicate that extremes of inactivity/activity can significantly influence insomnia risk independent of country. Insomnia risk associated with very low levels of activity may be mediated by poorer health and disadvantageous social status. However, while very high levels of activity increase insomnia risk independent of health and demographic factors, they may also confound with personally and occupationally demanding lifestyles.