Irregular Sleep Patterns Associated with Harmful Gut Bacteria

A new study is the first to find multiple associations between social jet lag  (the shift in your internal body clock when your sleeping patterns change between workdays and free days)  and diet quality, diet habits, inflammation and gut microbiome composition in a single cohort.

Previous research has shown that working shifts disrupts the body clock and can increase risk of weight gain, heart problems and diabetes. However, there is less awareness that our biological rhythms can be affected by smaller inconsistencies in sleeping patterns due to waking early with an alarm clock on workdays, for example, compared to waking naturally on non-work days for people working regular hours.

Senior author Dr Wendy Hall from King’s College London said: ” This is the first study to show that even small differences in sleep timings across the week seems to be linked to differences in gut bacteria species. Some of these associations were linked to dietary differences but our data also indicates that other, as yet unknown, factors may be involved. We need intervention trials to find out whether improving sleep time consistency can lead to beneficial changes in the gut microbiome and related health outcomes.”

The composition of the microbes in your gut (microbiome) may negatively or positively affect your health by producing toxins or beneficial metabolites. Specific species of microbes can correspond to an individual’s risk of long-term health conditions such as diabetes, heart disease and obesity. 

In a cohort of 934 people, researchers assessed blood, stool and gut microbiome samples as well as glucose measurements in those whose sleep was irregular compared to those who had a routine sleep schedule. 

Researchers found that just a 90-minute difference in the timing of the midpoint of sleep — the halfway point between sleep time and wake-up time — is associated with differences in gut microbiome composition.

Three out of the six microbiota species more abundant in the social jet lag group have ‘unfavorable’ associations with health. These microbes are associated with poor diet quality, indicators of obesity and cardiometabolic health, and markers in your blood related to higher levels of inflammation and cardiovascular risk.

First author Kate Bermingham, PhD, said: “Sleep is a key pillar of health, and this research is particularly timely given the growing interest in circadian rhythms and the gut microbiome. Even a 90-minute difference in the mid-point of sleep can encourage microbiota species which have unfavorable associations with your health.”


Kate M. Bermingham, Sophie Stensrud, Francesco Asnicar, Ana M. Valdes, Paul W. Franks, Jonathan Wolf, George Hadjigeorgiou, Richard Davies, Tim D. Spector, Nicola Segata, Sarah E. Berry, Wendy L. Hall. Exploring the relationship between social jetlag with gut microbial composition, diet and cardiometabolic health, in the ZOE PREDICT 1 cohort. European Journal of Nutrition, 2023; DOI: 10.1007/s00394-023-03204-x

King’s College London. “Irregular sleep patterns associated with harmful gut bacteria.” ScienceDaily. ScienceDaily, 2 August 2023. <>.

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Photo by Jp Valery