Sleep regularity is linked to sleep timing and body clock, affecting daytime function in delayed sleep phase disorder

In 170 patients with Delayed Sleep-Wake Phase Disorder, higher sleep regularity index scores were associated with earlier sleep onset and longer total sleep time.

• Higher sleep regularity index scores correlated with earlier sleep onset and longer total sleep duration.
• No significant relationship was found between sleep regularity, sleep quality, daytime function, or mood outcomes.
• Phase angle was directly associated with daytime functioning, sleep-related impairment, and mood outcomes.
• Sleep regularity index scores mediated the effects of sleep onset time and phase angle on daytime function.
• Total sleep time mediated the effects of sleep onset time and phase angle on sleep-related impairment.

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