Is the insula linked to sleep? A systematic review and narrative synthesis

BACKGROUND: Sleep is critical to human beings in a surprisingly diverse set of ways, and there is, thus, continual investigation into the mechanisms of sleep. Although current studies have confirmed that multiple brain regions are involved in the regulation of both sleep and wakefulness, the association between certain important brain regions such as the insula and sleep is still unclear. OBJECTIVE: The purpose of this study was to systematically review studies on the insula and sleep and to discuss the relationship between the insula and sleep. METHODS: We searched the PubMed and Web of Science Core Collection (WoSCC) for articles on sleep and the insula. The time span was from inception to June 30, 2022. The search results were then narratively summarized. RESULTS: A total of 939 studies were identified in the PubMed and WoSCC of which 115 studies were finally included in the narrative synthesis. These 115 studies can be roughly divided into 41 studies on insomnia, 39 on sleep deprivation, 33 on sleep-related experiments examining the insula, and 2 studies using basic experiments. CONCLUSION: The combined findings of many sleep-related studies have confirmed a close link between the insula and sleep loss, including insomnia, sleep deprivation, sleep-related disorders, and more. Although these results do not directly confirm that the insula is involved in sleep, a overall analysis of the results indicates that the insula may be a potential key brain region involved in sleep.