Links between sleep and body mass index in bipolar disorders: an exploratory study.

STUDY OBJECTIVES: Obesity and excess bodyweight are highly prevalent in individuals with bipolar disorders (BD) and are associated with adverse consequences. Multiple factors may explain increased bodyweight in BD including side effects of psychotropic medications, and reduced physical activity. Research in the general population demonstrates that sleep disturbances may also contribute to metabolic burden. We present a cross-sectional study of the associations between body mass index (BMI) and sleep parameters in patients with BD as compared with healthy controls (HC). METHODS: Twenty-six French outpatients with remitted BD and 29 HC with a similar BMI completed a 21-day study of sleep parameters using objective (actigraphy) and subjective (PSQI: Pittsburgh Sleep Quality Index) assessments. RESULTS: In BD cases, but not in HC, higher BMI was significantly correlated with lower sleep efficiency (P=0.009) and with several other sleep parameters: shorter total sleep time (P=0.01), longer sleep onset latency (P=0.05), higher fragmentation index (P=0.008), higher inter-day variability (P=0.05) and higher PSQI total score (P=0.004). CONCLUSIONS: The findings suggest a link between a high BMI and several sleep disturbances in BD, including lower sleep efficiency. Physiological mechanisms in BD cases may include an exaggeration of phenomena observed in non-clinical populations. However, larger scale studies are required to clarify the links between metabolic and sleep-wake cycle disturbances in BD.