Age and Sex as Moderators of Sleep Architecture in Schizophrenia, Bipolar Disorder, and Unipolar Depression: A Case-Control Polysomnographic Systematic Review and Meta-Regression

Abstract

Sleep architecture alterations are consistently reported across major psychiatric disorders, but the contribution of demographic factors to between-study heterogeneity remains insufficiently characterized. Age and sex have not been systematically examined as study-level moderators across harmonized case-control polysomnographic evidence spanning psychotic and mood disorders. A transdiagnostic systematic review and meta-regression of case-control polysomnographic studies compared schizophrenia, bipolar disorder and unipolar depression with healthy controls. Eligible studies reported diagnostic criteria, treatment status, age and sex. Standardized mean differences were synthesized using random-effects models with REML estimation. Univariable mixed-effects meta-regressions assessed age and sex as moderators within each diagnostic group. Age and sex moderated delta sleep-related effect sizes in schizophrenia and unipolar depression. Age also moderated sleep continuity and sleep duration effect sizes in unipolar depression and REM sleep-related effect sizes across all disorders. Sex moderated delta sleep duration and REM density in bipolar mania. No significant effects were observed in bipolar depression. These effects were heterogeneous and not consistently observed across disorders or sleep parameters. Overall, demographic composition explains only a modest proportion of heterogeneity. Interpretation is limited by the ecological nature of study-level meta-regression and residual between-study heterogeneity.