Effects of cognitive behavioral therapy for insomnia on subjective and objective measures of sleep and cognition

To assess the effects of Cognitive Behavioral Therapy for insomnia (CBTi) on subjective and objective measures of sleep, sleep-state misperception and cognitive performance. We performed a randomized-controlled trial with a treatment group and a wait-list control group to assess changes in insomnia symptoms after CBTi (8 weekly group sessions/3 months) in 62 participants with chronic insomnia. To this end, we conducted a multimodal investigation of sleep and cognition including subjective measures of sleep difficulties (Insomnia Severity Index [ISI]; sleep diaries) and cognitive functioning (Sahlgrenska Academy Self-reported Cognitive Impairment Questionnaire), objective assessments of sleep (polysomnography recording), cognition (attention and working memory tasks), and sleep-state misperception measures, collected at baseline and at 3-months post-randomization. We also assessed ISI one year after CBTi. Our main analysis investigated changes in sleep and cognition after 3 months (treatment versus wait-list). While insomnia severity decreased and self-reported sleep satisfaction improved after CBTi, we did not find any significant change in objective and subjective sleep measures (e.g., latency, duration). Degree of discrepancy between subjective and objective sleep (i.e., sleep misperception) in sleep latency and sleep duration decreased after CBTi suggesting a better perception of sleep after CBTi. In contrast, both objective and subjective cognitive functioning did not improve after CBTi. We showed that group-CBTi has a beneficial effect on variables pertaining to the subjective perception of sleep, which is a central feature of insomnia. However, we observed no effect of CBTi on measures of cognitive functioning.