Sleep variability in delayed sleep-wake phase disorder and insomnia disorder in youth: A case-control study
Published in Sleep Medicine, 2026
Yue Pan#, Forrest Tin Wai Cheung#, Joey Wing Yan Chan, Ngan Yin Chan, Xiao Li, Amy Wing Yin Ho, Chung Shun Ho, Michael Gradisar, Yun-Kwok Wing, Shirley Xin Li
#Contributed equally to this work.
Abstract
Objectives
To compare intraindividual sleep variability in youths with delayed sleep-wake phase disorder (DSWPD) and insomnia disorder (ID), and to examine the association of sleep variability with depressive symptoms and circadian measures.
Methods
Youths with DSWPD (n = 34, Mage = 20.7 ± 1.7, 70.6% female), ID (n = 40, Mage = 20.3 ± 2.4, 70.0% female) and healthy sleepers (n = 39, Mage = 19.7 ± 2.1, 66.7% female) completed a battery of self-report questionnaires, sleep diary for eight days with actigraphy monitoring, and laboratory-based dim light melatonin onset (DLMO) assessment. Subjective and objective intraindividual variability in sleep parameters were derived from sleep diary and actigraphy data, respectively.
Results
Compared with youths with ID, those with DSWPD showed greater variability in diary-derived bedtime (p = .006), time in bed (p = .010), and total sleep time (p = .013). Relative to healthy sleepers, the DSWPD group showed greater variability in diary-derived total sleep time (p = .017) and actigraphy-derived wake after sleep onset (p = .040). Both clinical groups showed greater variability in diary-derived sleep onset latency compared with healthy sleepers (DSWPD: p = .011; ID: p < .001). Later DLMO times and higher levels of depressive symptoms were significantly associated with increased sleep variability across the full sample.
Conclusions
Youths with DSWPD and ID show heightened sleep variability, linked to delayed circadian rhythm and elevated depressive symptoms. Findings highlight the clinical relevance of intraindividual sleep variability. Further prospective and interventional studies are needed to delineate the mechanistic processes associated with increased sleep variability in these conditions.
Recommended citation: Pan, Y., Cheung, F. T. W., Chan, J. W. Y., Chan, N. Y., Li, X., Ho, A. W. Y., ... & Li, S. X. (2026). Sleep variability in delayed sleep-wake phase disorder and insomnia disorder in youth: A case-control study. Sleep Medicine, 108859.
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