LAUSR

STUDY OBJECTIVES Sleep schedule consistency is fundamental to cognitive behavioral therapy for insomnia (CBT-I), although there is limited evidence suggesting whether it predicts treatment response. This analysis tested whether: (1) an Internet-based CBT-I program affects intra-individual variability (IIV) in sleep schedule, and (2) sleep schedule IIV predicts insomnia symptom remission. METHODS This secondary analysis compares participants (N=303) randomized to an Internet-based CBT-I program (SHUTi - Sleep Healthy Using the Internet) or Internet-based patient education (PE). Participants reported daily bedtimes and rising times on ten online sleep diaries collected over two weeks at baseline and nine-week post-intervention assessment. Participants completed the Insomnia Severity Index (ISI) at post-assessment and six-month follow-up; symptom remission was defined by ISI<8. Mixed effects location scale modeling was used to examine the effect of SHUTi on bedtime and rising time IIV; a novel two-staged analysis examined the effect of bedtime and rising time IIV on insomnia symptom remission. RESULTS At post-assessment, SHUTi participants reported about 30% less bedtime and 32% less rising time variability compared to PE (ps<.03). Bedtime and rising time IIV was not independently associated with likelihood of insomnia symptom remission at the subsequent time point (ps>.18), nor did sleep schedule IIV moderate treatment response (ps>.12). CONCLUSIONS Findings demonstrate that an Internet-delivered CBT-I program can effectively increase users' sleep schedule consistency relative to an educational control. This consistency, however, was not related to treatment outcome when defined by insomnia symptom remission, suggesting that enforcing rigid sleep schedules for patients may not be necessary for treatment success.