Abstract
Background: Sleep and circadian rhythm disturbances in schizophrenia are common, but incompletely characterised. We aimed to describe and compare the magnitude and heterogeneity of sleep-circadian alterations in remitted schizophrenia, and compare them with those in inter-episode bipolar disorder. Methods: EMBASE, Medline, and PsycINFO were searched for case-control studies reporting actigraphic parameters in remitted schizophrenia or bipolar disorder. Standardised and absolute mean differences between patients and controls were quantified using Hedges-g, and patient-control differences in variability were quantified using the mean-scaled coefficient of variation ratio (CVR). A wald-type test compared effect-sizes between disorders. Results: Thirty studies reporting on 967 patients and 803 controls were included. Compared to controls, both schizophrenia and bipolar groups had significantly longer total sleep time (mean difference (minutes) [95%CI] = 99.9 [66.8, 133.1] and 31.1 [19.3, 42.9], respectively), time in bed (MD = 77.8 [13.7, 142.0] and 50.3 [20.3, 80.3]), but also greater sleep latency (16.5 [6.1, 27.0] and 2.6 [0.5, 4.6]) and reduced motor activity (SMD [95%CI] = -0.86 [-1.22, -0.51] and -0.75 [-1.20, -0.29]). Effect sizes were significantly greater in schizophrenia compared to the bipolar disorder group for total sleep time, sleep latency, and wake after sleep onset. CVR was significantly elevated in both diagnoses for total sleep time, time in bed, and relative amplitude. Conclusions: In both disorders, longer overall sleep duration, but also disturbed initiation, continuity and reduced motor activity were found. Common, modifiable factors may be associated with these sleep-circadian phenotypes, and advocate for further development of transdiagnostic interventions that target them.