SLOW WAVE SLEEP AND RESPONSE TO COGNITIVE BEHAVIORAL THERAPY FOR INSOMNIA

Introduction Cognitive Behavioral Therapy for Insomnia (CBT-I) is recognized to be the first-choice treatment for chronic insomnia. Since the subjective evaluation of nocturnal sleep in mandatory for the diagnosis of insomnia, the efficacy of CBT-I has been mostly investigated with subjective measures. Only few studies examined the efficacy of CBT-I with an objective evaluation. However, polysomnography (PSG) could provide important information regarding objective sleep phenotypes and its influence on CBT-I response. Aim of our study was to evaluate if PSG variables before treatment could predict CBT-I outcomes. Methods 29 chronic insomnia patients (15 females and 14 males, mean age 40.8±12.0) underwent an ambulatory PSG recording before CBT-I treatment. Patients also reported subjective sleep by means of sleep diary during PSG evaluation and throughout the duration of CBT-I (9 weeks). PSG data were used as primary outcomes to evaluate possible different response to CBT-I. Moreover, we used a general linear model to assess if any PSG sleep measures could predict patients’ response to CBT-I in terms of Insomnia Severity Index (ISI) or subjective sleep diary variables. Results All patients demonstrated a significant improvement after CBT-I both at ISI (19.1±3.7 vs 10.8±4.9; p=.000) and at sleep variables (Sleep Latency: 38.1±28.6 vs 22.9±22.5, p=.005; Wake after Sleep Onset (WASO): 98.6±79.9 vs 51.7±52.1, p=.002; Sleep Efficiency: 67.2±19.1 vs 82±11.9, p=.000).The general linear model analysis with PSG data showed that only Slow Wave Sleep (SWS) % predicted the decrease of WASO subjectively reported at Sleep Diaries. In particular, patients by a higher SWS % were the ones showing a greater improvement at WASO after CBT-I (98.6±79.9 vs 51.7±52.2; p= .032). Conclusion Our study demonstrated that SWS % before treatment predict a better response to CBT-I. This result might support the hypothesis of a possible phenotype of insomnia characterized by % of SWS that could be the natural mediator of “process S” pressure that would result in a greater improvement of subjectively reported WASO and therefore in a better outcome after CBT-I.