Sleep and circadian alterations in people at risk for bipolar disorder: A systematic review

Abstract Background Sleep and circadian abnormalities have been mostly demonstrated in bipolar patients. However, it is not clear whether these alterations are present in population at high risk for bipolar disorder (BD), indicating a possible risk factor for this condition. Objective This systematic review aims to define current evidence about sleep and rhythm alterations in people at risk for BD and to evaluate sleep and circadian disorders as risk factor for BD. Methods The systematic review included all articles about the topic until February 2016. Two researchers performed an electronic search of PubMed and Cochrane Library. Keywords used were ‘sleep’ or ‘rhythm’ or ‘circadian’ AND ‘bipolar disorder’ or ‘mania’ or ‘bipolar depression’ AND ‘high-risk’ or ‘risk’. Results Thirty articles were analyzed (7451 participants at risk for BD). Sleep disturbances are frequent in studies using both subjective measures and actigraphy. High-risk individuals reported irregularity of sleep/wake times, poor sleep and circadian rhythm disruption. Poor sleep quality, nighttime awakenings, and inadequate sleep are possible predictive factors for BD. A unique study suggested that irregular rhythms increase risk of conversion. People at risk for BD showed high cortisol levels in different times of day. Studies about anatomopathology, melatonin levels, inflammatory cytokines and oxidative stress were not identified. The most important limitations were differences in sleep and rhythm measures, heterogeneity of study designs, and lack of consistency in the definition of population at risk. Conclusion Sleep and circadian disturbances are common in people at risk for BD. However, the pathophysiology of these alterations and the impact on BD onset are still unclear.