Actigraphic assessment of delayed sleep–wake rhythm could predict functional impairment in patients with bipolar disorder

A delayed sleep-wake rhythm is a common but often under-recognized characteristic of bipolar disorder (BD). This study aimed to examine the association between delayed sleep-wake rhythm and functional impairment using actigraphy. Participants with BD in clinical remission (N = 47) were recruited. Sleep parameters, including the midpoint of sleep (o'clock), total sleep time (minutes), sleep efficiency (%), and wake after sleep onset (minutes), were averaged over a 14-day period using continuous actigraphy. Functional impairment was assessed using the 12-item World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0). Correlation analyses were conducted to examine associations between total WHODAS 2.0 scores and sleep parameters. Multiple regression analyses were performed with WHODAS 2.0 total scores as the dependent variable and sleep parameters as independent variables, controlling for mood symptoms and insomnia severity. Correlation analysis revealed a significant positive relationship between the midpoint of sleep and total WHODAS 2.0 scores (r = 0.424, p = 0.003). Multiple regression analysis identified the midpoint of sleep as a significant predictor of total WHODAS 2.0 scores (β = 0.488, p = 0.005). Delayed sleep-wake rhythms may contribute to functional impairment in euthymic individuals with BD. These findings suggest that advancing sleep-wake rhythm may contribute to improvements in social functioning. Actigraphy holds potential as a digital biomarker for assessing functional outcomes in this population.