The epidemiology of sleep and obesity.

Sleep is a state of consciousness that is preserved across animal species whose exact function is not yet clear but which has a vital impact on health and well-being. Epidemiological evidence suggests sleep duration in both children and adults has been decreasing over the past half-century, while at the same time rates of overweight and obesity have been increasing. Short sleep duration along with other dimensions of poor sleep has been associated with obesity both cross-sectionally and longitudinally. These data suggest a potential causal relationship between poor sleep and greater rates of weight gain that may be related to effects of sleep on dietary intake or physical activity. However, there is also potential for reverse causation as obesity leads to many co-morbidities including sleep apnea that can disrupt sleep. Medium and long term interventional studies are needed to evaluate the potential for healthy sleep interventions to help combat the epidemic of obesity.