Sleep problems are rarely limited to the hours of the night; when sleep is disrupted, its effects are reflected the next day in the form of a lack of energy, difficulty concentrating, and a volatile mood. Over time, these problems can increase the risk of serious health conditions.
For many years, scientists have focused primarily on the brain to explain the wide-ranging effects of sleep disorders. But this perception has begun to change with the emergence of new research suggesting that the gut plays an important role in the sleep story.
A comprehensive scientific review of previous studies shed light on this relationship more clearly. By analyzing the results of dozens of studies rather than relying on individual small studies, researchers came to a clear pattern.
People with chronic sleep problems often show consistent changes in gut bacteria, suggesting that sleep health is linked to a broader biological system than previously thought.
The Relationship Between Sleep and Gut Health
To understand this relationship, researchers reviewed studies published up to late 2025, comparing the gut bacteria of people with sleep disorders and healthy individuals.
The final review included more than 50 studies and about 17,000 participants, addressing conditions such as “insomnia”, “obstructive sleep apnea”, “REM sleep behavior disorder (RBD)”, and poor sleep quality, as well as sleeping for abnormally short or long periods.
Across these different cases, one trend was clearly repeated:
People with long-term sleep disorders tend to have less diversity in their gut bacteria, i.e., fewer bacterial species and a weaker balance in the gut environment.
The clearest changes were associated with “insomnia” and “obstructive sleep apnea”, two conditions characterized by frequent disruption of the natural sleep pattern.
In contrast, temporary sleep deprivation or short-term changes in sleep timing showed limited or inconsistent effects on gut bacteria, suggesting that the gut is more affected by chronic sleep problems.
In addition to overall diversity, the review examined changes in specific bacterial types. Researchers noted that a number of sleep disorders, despite their different symptoms, share similar microbial patterns.
A decrease in the levels of beneficial bacteria that maintain gut health and reduce inflammation was observed. “Faecalibacterium” bacteria frequently stood out across several disorders.
This bacterium plays an essential role in protecting the lining of the intestine and producing “Butyrate”, an important compound in regulating inflammation.
The levels of this bacteria decreased in people with “insomnia”, “obstructive sleep apnea”, “REM sleep behavior disorder”, and poor sleep quality. A decline in “Lachnospira” bacteria, which is also a butyrate producer, was also recorded in several cases.
In contrast, levels of some bacteria associated with inflammation increased in some disorders. Among them is “Collinsella” bacteria, associated with metabolic and immune problems, which appeared at higher levels in people with “insomnia” and “REM sleep behavior disorder”.
These changes collectively indicate a gut environment that tends toward inflammation more than balance.
