Abstract
STUDY OBJECTIVES: The aim of this study was to test the efficacy of fully automated Internet-delivered cognitive behavioral therapy for insomnia (CBT-I) 18 months after the intervention period on sleep, daytime functioning, and beliefs about sleep for adults with chronic insomnia. METHODS: Participants in this study had participated in a randomized controlled trial comparing the efficacy of unguided Internet CBT-I with web-based patient education. Participants who had received Internet CBT-I (n = 95) completed online questionnaires and online sleep diaries 18 months after the intervention period. We used linear mixed models to study changes from baseline to postassessment and to 18-month follow-up, and a separate mixed-models analysis to study changes from postassessment to 18-month follow-up. RESULTS: Mean age of the participants was 45.5 years (standard deviation = 12.6) and 64% were females. Sixty-six participants (70%) completed the 18-month follow-up assessment. There were significant improvements from baseline to 18-month follow-up on the Insomnia Severity Index (ISI) (Cohen d = 2.04 [95% confidence interval (CI) 1.66-2.42]) and the Bergen Insomnia Scale (BIS) (d = 1.64 [95% CI 1.30-1.98]), levels of daytime fatigue (d = 0.85 [95% CI 0.59-1.11]), psychological distress (d = 0.51 [95% CI 0.29-0.73]), and beliefs about sleep (d = 1.44 [95% CI 1.15-1.73]). Moderate to large effect size improvements were also shown on the diary-derived sleep variables. All improvements from baseline to postassessment were essentially maintained to 18-month follow-up. CONCLUSIONS: Unguided Internet CBT-I appears to have sustained effects on sleep, daytime functioning, and beliefs about sleep up to 18 months after the intervention period. CLINICAL TRIAL REGISTRATION: This study presents long-term follow-up data of a previous clinical trial. Registry: ClinicalTrials.gov, Title: Internet-based Treatment for Insomnia in Norway, Identifier: NCT02261272, URL: https://clinicaltrials.gov/ct2/show/NCT02261272.