Proportion and Associated Clinical Factors of Paradoxical Insomnia in Patients With Chronic Insomnia: A Retrospective and Observational Study

Abstract

Objectives: Paradoxical insomnia, a type of sleep disorder, is characterized by misperception and underestimation of an individual’s sleep time. In this study, we investigated the percentage and clinical factors associated with paradoxical insomnia in patients with chronic insomnia, who underwent polysomnography.Methods: The study included 148 patients with chronic insomnia. The study population was categorized into paradoxical and non-paradoxical insomnia groups. The following criteria were used to define paradoxical insomnia: 1) total sleep time >390 min and sleep efficiency ≥85.0%, and 2) significant discrepancy of >1 hour between subjective and objective sleep measurements. We analyzed demographic data, polysomnographic parameters, and perceived sleep time in all patients.Results: Among 148 patients with chronic insomnia, 33 (22.6%) had paradoxical insomnia. We observed significant intergroup differences in age, sex, and the Insomnia Severity Index (ISI). Sleep architecture patterns were relatively better in the paradoxical than in the non-paradoxical insomnia group. Logistic regression analysis was performed to determine clinical factors associated with paradoxical insomnia. Female sex (odds ratio [OR] 2.96, 95% confidence interval [CI] 1.19–7.37), age (OR 0.97, 95% CI 0.94–0.99), and ISI (OR 1.18, 95% CI 1.05–1.31) were significantly associated with paradoxical insomnia.Conclusions: Approximately 20.0% of patients with chronic insomnia were classified into the paradoxical insomnia group, and female sex, age, and ISI were identified as clinical factors associated with this type of sleep disorder.