What is the nature of sleep and circadian rhythm health on gastrointestinal microbiota? A systematic review of studies in humans.

This systematic review synthesized findings from 41 human studies across the lifespan published between 2016 and 2025 examining associations of multidimensional sleep and circadian rhythm health with the gut microbiome (GM). The studies include experimental and observational designs of generally healthy participants, measuring sleep and circadian dimensions such as duration, quality, insomnia, and circadian disruptions (e.g., shift work). Results suggest sleep truncation, disturbances, and circadian misalignment may be linked to GM composition and function, though results were mixed on microbial diversity. The heterogeneous evidence suggests that the microbial family Oscillospiraceae/Ruminococcaceae is often associated with sleep and circadian metrics, warranting rigorous inquiry of taxa within this family. Functional outputs of the GM were infrequently assessed, but when measured, identified functions in amino acid and fatty acid metabolism, and vitamin, hormone/neurotransmitter, phosphate, short-chain fatty acid, and bile acid pathways. Inconsistencies in findings may reflect differing analytical methods, participants' age, health status, and lifestyle (e.g., diet, physical activity). Future investigations should prioritize longitudinal and experimental, multi-omics studies to clarify causal pathways and assess interventions, especially in populations with sleep disruption. Findings underscore the potential for sleep and circadian interventions to support GM balance and improve health outcomes.