Sleep variability and its association with circadian biomarker and depressive symptoms in youths with delayed sleep phase disorder and insomnia disorder

Yue Pan, Forrest Tin Wai Cheung, Joey Wing-Yan Chan, Ngan Yin Chan, Xiao Li1, Yun-Kwok Wing, Shirley Xin Li

Abstract

Introduction Insomnia disorder and delayed sleep phase disorder (DSPD) share similar clinical symptoms, such as difficulty falling asleep, yet they may be linked to different pathophysiological processes. Intraindividual variability (IIV) in sleep may be an important feature to consider given its implications for mental and physical health outcomes. This case-control study aimed to compare sleep IIV in delayed sleep phase disorder, insomnia disorder, and healthy sleepers, and to examine the association of IIV with dim light melatonin onset (DLMO) time and depressive symptoms.

Methods Youth participants with DSPD (N = 39, Mage = 20.54 ± 1.83, 69.2% female) and insomnia disorder (N = 40, Mage = 20.60 ± 2.01, 67.5% female) diagnosed according to the ICSD-3 criteria, as well as healthy sleepers (N = 40, Mage = 19.53 ± 2.25, 67.5% female) were invited to complete a set of questionnaires on sleep- and mood-related symptoms, 7-day sleep diary with actigraphy monitoring, and a one-night laboratory-based DLMO assessment. Subjective and objective IIV were calculated using root mean squared successive differences from sleep diary and actigraphy data.

Results Compared to control group, both DSPD and insomnia groups had greater IIV in subjective and objective sleep onset latency (SOL) (both p < 0.001), later DLMO time (DSPD: p < 0.001; insomnia: p = 0.041) and more severe depressive symptoms (DSPD: p < 0.001; insomnia: p = 0.004). Only the DSPD group showed greater IIV in subjective time in bed (TIB) (p = 0.042) and total sleep time (TST) (p = 0.015). Additionally, DSPD group showed greater IIV in subjective TIB (p = 0.009), TST (p = 0.034) and more severe depressive symptoms (p = 0.029) compared to insomnia group. Regression analyses indicated that greater sleep IIV in both subjective (β = 0.24, p = 0.014) and objective SOL (β = 0.31, p = 0.001) were significantly associated with later DLMO time. However, only IIV in subjective SOL was associated with depressive symptoms (β = 0.20, p = 0.042).

Conclusion This study showed that youths with DSPD and insomnia disorder exhibited greater sleep IIV, which was associated with later circadian time and more severe depressive symptoms. These findings may have the implications for understanding the link among sleep, circadian and mood disturbance in relation to DSPD and insomnia disorder. Further research may consider examining the intervention effects on sleep IIV in the context of DSPD and insomnia disorder.

Recommended citation: Pan, Y., Cheung, F. T. W., Chan, J. W. Y., Chan, N. Y., Li, X., Wing, Y. K., & Li, S. X. (2024). Sleep variability and its association with circadian biomarker and depressive symptoms in youths with delayed sleep phase disorder and insomnia disorder. Journal of Sleep Research, 33(Suppl.1).