Sleep duration and obesity in adulthood: an updated systematic review and meta-analysis

Short and long sleep duration have been associated with risk of obesity in children and adolescents. Evidence in adults is more mixed, with biological and psychosocial factors underlying these relationships mostly unknown. This review aimed at qualitatively and quantitatively summarizing previous studies on sleep duration as a predictor of obesity in adults in order to provide an update of the state of art in this field and clarify these relationships. Odds ratios at 95% Confidence Intervals (CI) were estimated using random-effects models. Heterogeneity of effects distribution and publication bias were tested. Twelve articles were selected for short sleep (n = 154,936) and eight for long sleep duration (n = 152,192). Results indicated that short sleep duration (OR: 1.412; 95% CI: 1.177-1.694) was significantly associated with the risk of future obesity, and that long sleep duration (OR: 0.995; 95% CI: 0.889-1.114) was not associated. Heterogeneity was high and lowered to non-significant values when considering gender and extremes of short/long sleep duration. Results seem to confirm a potential role of short sleep duration in predicting but results on long sleep are still mixed. Future investigations on potential mediators of such relationships are needed.