Altered sleep architecture in chronic insomnia and its phenotypes: polysomnographic correlates and associations with insomnia severity and depressive symptoms

Aim: The aim of this study was to evaluate clinical and polysomnographic differences in sleep architecture between patients with chronic insomnia (CI) and healthy controls (HC), as well as between CI phenotypes with short and normal sleep duration. Materials and methods: This cross-sectional study included 35 patients with CI and 27 age- and sex-matched HC. All participants completed the Insomnia Severity Index (ISI) and Beck Depression Inventory (BDI) and underwent single-night home polysomnography. Based on 14-day sleep diaries, patients were categorized into insomnia with self-reported short sleep duration (ISSD; <6 h) and insomnia with self-reported normal sleep duration (INSD; ≥6 h). Group comparisons and correlation analyses were performed. Results: Compared with HC, CI patients showed significantly higher ISI and BDI scores, increased total wake time (TWT), wake after sleep onset (WASO), and N2 sleep duration, along with reduced N3 sleep and sleep efficiency (SE). No significant differences were observed in total sleep time or sleep latency. ISSD patients demonstrated significantly higher questionnaire scores, shorter TST, and reduced REM sleep compared with INSD. ISI correlated positively with BDI, TWT, SL, and WASO and negatively with sleep efficiency. Conclusion: CI is associated with objective alterations in sleep architecture, particularly increased nocturnal wakefulness and reduced deep sleep. The ISSD phenotype appears clinically more severe, with greater symptom burden and reduced REM sleep, supporting the value of combining subjective and objective measures in insomnia phenotyping.