Almost a third of our lives are spent sleeping. Necessary for the body to function properly, sleep should not be neglected. We now know that reducing the amount or quality of sleep has an impact on several functions. But did you know that going to bed at irregular hours also has an impact on the intestinal microbiota? At least, that’s what a recently published British study suggests.

Social jetlag: a shifted sleep pattern

Sleep can be altered by several factors, whether associated with lifestyle (screens, night work, etc.) or the environment (lights, etc.). Research has shown that it disruption can have harmful effects on various aspects of health:

  • Vigilance
  • Memory
  • Replenishment of energy stores
  • Hormone production
  • Regulation of various functions
  • Immunity

And now there’s a new kind of change. New data suggests that a shifted sleep pattern between weekdays and weekends (or days off) could have consequences for the intestinal microbiota.

This change in rhythm is known as “social jetlag“. Nearly 40% of the population is thought to be affected.

It is defined as a difference of one hour or more in sleep between days with and without work.  In other words, this is explained by going to bed and getting up later at weekends to enjoy the evenings. Nevertheless, the quality of sleep is altered, making it less restorative.

Few data exist on the health effects of such an upheaval. That’s why a British team has conducted a clinical study to find out.

A clinical trial involving almost 1,000 people

In a cohort study, researchers at King’s College recruited 934 healthy adults who slept an average of 7 hours a night during the week. They then distinguished between two groups:

  • People who slept more at weekends than during the week (around 1h30 more),
  • Those whose sleep pattern remained unchanged.

After analysing the participants’ faeces, cardiometabolic markers and diet, shifting their sleep by 1h30 at the weekend would disrupt:

  • Circadian rhythm
  • Diet, in terms of habits and quality (consumption of less healthy, sweeter foods, less diversified by reducing portions of fruit and nuts)
  • Intestinal microbiota, which appears dysbiotic. Just 90 minutes more sleep at the weekend would allow the development of harmful toxin-producing bacteria (including Clostridia and Peptococcaceae) and reduce the proportion of good bacteria. And this is all down to poor diet.

Researchers note that Clostridia and Peptococcaceae are associated with certain pathologies such as obesity and cardiometabolic diseases. They are also thought to contribute to the development of inflammation and cardiovascular diseases.

Researchers are therefore recommending that, to maintain good health, people should not shift their sleep between weekdays and weekends.



Picture: Freepik

BERMINGHAM KM, STENSRUD S, ASNICAR F, VALDES AM, FRANKS PW, WOLF J, HADJIGEORGIOU G, DAVIES R, SPECTOR TD, SEGATA N, BERRY SE, HALL WL. Exploring the relationship between social jetlag with gut microbial composition, diet and cardiometabolic health, in the ZOE PREDICT 1 cohort. Eur J Nutr. 2023