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Abstract Introduction Sleep-wake state discrepancy, characterized by a difference in objectively and subjectively evaluated sleep, is common among individuals with insomnia. While it was hypothesized that hyperarousal might play a role, there has been limited research to examine self-reported pre-sleep arousal and objectively measured cortical arousal in youth insomnia. The current study aimed to explore the potential differences in subjective and objective hyperarousal between youths with insomnia and healthy sleepers, and to examine whether hyperarousal mediated the association between sleep-wake state discrepancy and insomnia severity. Methods Sixty-six youths with DSM-5 insomnia disorder (age:20.03±2.31; female: 62.12%) and 40 healthy controls (age:19.52±2.25; female: 65%) were included. Participants completed a 7-day prospective sleep diary and actigraphy monitoring, a single-night in-lab polysomnography assessment, and self-reported questionnaires including Insomnia Severity Index for the measure of insomnia severity and Pre-sleep Arousal Scale (PSAS) for the measure of cognitive and somatic hyperarousal. The discrepancy sleep indices were computed by subtracting the data from 7-day actigraphy and sleep diary, where a positive value indicated a subjective underestimation. Results There was a significant group difference in sleep-wake state discrepancy in sleep onset latency (13.71 minutes overestimation in the insomnia group vs. 7.44 minutes underestimation in the control group). Moreover, relative to the healthy control group, the insomnia group showed significantly more severe insomnia (p.01) and higher levels of pre-sleep cognitive and somatic arousal (p.01), beta-band activity in non-rapid eye movement stage 1 (p.05), stage 2 (p.05), and rapid-eye movement stage (p.05). Subjectively reported pre-sleep cognitive and somatic arousal, but not objective arousal indices, were found to mediate the association between sleep-wake state discrepancy in sleep onset latency and insomnia severity (ab=-0.39, p.01 ). Conclusion Both subjectively and objectively measured hyperarousal is present in youth insomnia. The mediating effect of subjective pre-sleep arousal on the association between sleep-wake state discrepancy and insomnia severity warrants further neuroimaging research on its underlying mechanism. Future studies should also consider exploring the effects of insomnia treatment on self-perceived sleep-related arousal and sleep-wake state discrepancy in youth. Support (if any) This work was funded by General Research Fund (Ref. 17613820 and 17613321), Research Grants Council, University Grants Committee, Hong Kong SAR, China
WANG et al. (Sat,) studied this question.