0458 Earlier CBT-I Start Leads to Quicker Symptom Improvement in Patients with Chronic Insomnia Disorder

Introduction Insomnia is the most common sleep disorder, with approximately 15% of adults meeting criteria for chronic insomnia disorder (CID). Cognitive-behavioral therapy for insomnia (CBT-I) is the first-line guideline-recommended treatment, supported by strong evidence for its short- and mid-term efficacy. However, less is known about how the timing of CBT-I initiation influences insomnia symptom severity in routine clinical practice. Methods Participants included a pool of 121 adults (47.99±15.8 years old, 69% female, 17.1% minority) who received CBT-I for CID at the Behavioral Sleep Medicine (BSM) program of Penn State Health Sleep Research & Treatment Center. Participants completed the Insomnia Severity Index (ISI) at their consultation visit and each subsequent treatment visit. Linear mixed-effects models tested changes in ISI across CBT-I sessions, adjusting for sex, age, race/ethnicity, psychiatric and medical comorbidities, comparing patients who initiated treatment at their consultation visit (52.5%) versus those who initiated treatment at least 2-weeks after (47.5%). Results There was a significant main effect of CBT-I session on ISI scores, indicating decreasing ISI across the 8 sessions (F(7,4543)=36.88, p<.001). There was a significant interaction between timing of treatment initiation (initiation at consultation vs initiation ≥2 weeks later) and CBT-I sessions, with patients who initiated CBT-I at consultation showing a steeper decline in ISI across sessions compared with those who started later ((F(7,4542)=2.59, p=.013). Specifically, patients who initiated treatment at consultation demonstrated significantly lower ISI scores through sessions 2 to 4. Conclusion Initiating CBT-I at the time of consultation produced a faster early reduction in insomnia severity, though both immediate and delayed treatment groups showed substantial ISI improvements by the last session. These findings highlight the clinical value of obtaining two weeks of sleep diary data upon referral and prior to consultation, enabling clinicians to accurately assess patients' sleep-wake patterns and begin evidence-based treatment at the time of case formulation and patient feedback. Support (if any)