The microbiota-gut-brain axis in sleep disorders

Sleep is a complex physiological process and is a critical determinant of physical and mental health. In the past decades, significant progress has been made in understanding the neural mechanisms of sleep and awakening. However, the initiation and maintenance of the sleep-wake cycle is regulated not only by the central system but is also affected by signals from peripheral tissues. Growing evidence shows that the microbiota-gut-brain axis contributes to the regulation of sleep behavior both directly and indirectly and may play a critical role in the etiology and pathogenesis of sleep disorders. Sleep deprivation leads to dysfunction of gut microbiota and sleep disorders are accompanied by altered gut microbiota composition. In this review, we describe the bidirectional relationships between sleep and gut microbiota and summarize the abnormal characteristics of gut bacteria in distinct conditions including sleep disturbances, sleep disorders and sleep disorders comorbid with neuropsychiatric disorders. We also examine the potential routes of microbiota-gut-brain axis in sleep and gut microbiome interactions, including metabolic, immune, and neural pathways, and propose microbiota-targeted interventions for improving sleep. Manipulating gut microbiota may be a promising avenue for the development of novel interventions for sleep disorders.