Insomnia: the gut microbiome connection, prospects for probiotic and postbiotic therapies, and future directions

The gut microbiota is influenced by a complex interplay of factors including the host's genetics, diet, and lifestyle. It plays a crucial role in regulating metabolic processes and is linked to various diseases. Growing evidence suggests that the gut-brain axis, which involves bidirectional communication between the gut microbiota and the brain, plays a crucial role in regulating sleep patterns and has significant implications in the development of sleep disorders. This comprehensive review aims to summarize the current knowledge on the mechanisms underlying insomnia and its association with the gut microbiota and metabolome. Probiotics and postbiotics are beneficial microorganisms and their components and metabolites, which offer potential in modulating the gut microbiota of the host and alleviating insomnia. We present an overview of recent progress in probiotic and postbiotic intervention trials for managing insomnia, highlighting both the potential benefits and limitations of existing research in this domain. Additionally, we offer suggestions for future directions in this field. Probiotics can regulate sleep-wake behavior by modulating gut microbiota and its metabolites, influencing endocrine, neuronal, and immune responses. In addition, to understand the role of probiotics in improving insomnia, a standardized sleep behavior index and sleep monitoring method are needed.