Irregular sleep patterns, caused by ‘social jet lag’ – the shift in a person’s internal body clock when sleeping patterns change between workdays and free days – are associated with harmful gut bacteria and adverse health outcomes, in a new study undertaken by King’s College London (KCL).
Gut bacteria linked to ‘unfavourable’ health outcomes, such as inflammation and obesity, were more abundant in people who experience social jet lag.
Maintaining regular sleep patterns, including a consistent waking up time and bedtime, are both adjustable lifestyle behaviours that could improve health outcomes by allowing the body to maintain a healthy gut biome.
The findings are the first to show how social jetlag can impact health and are published in The European Journal of Nutrition.
Previous research has shown that changing sleep patterns, such as working night shifts, can negatively affect your health, but the researchers were interested in how more minor shifts in sleeping patterns, such as the differences between weekday and weekend sleeping habits, can affect health.
The composition of microbes in a person’s gut, known as the gut microbiome, can negatively or positively affect health, depending on the composition of gut bacteria and the amount of toxins or beneficial metabolites they produce. The gut biome is influenced by diet, and some species of microbes in the gut have been associated with an increased risk of long-term health conditions such as diabetes and heart disease.
As part of the ZOE PREDICT study, researchers analysed the sleep patterns of nearly 1,000 participants and assessed blood, stool and gut microbiome samples as well as glucose measurements. One cohort with irregular sleep was compared to another with a routine sleep schedule. All participants were healthy and lean, and slept for over seven hours a night throughout the week.
A 90-minute difference in the timing of the midpoint of sleep, the halfway point between when a person goes to sleep and when they wake up, is associated with changes in the gut microbiome. Social jet lag was thought to influence the gut microbiome because it is associated with lower overall diet quality, higher intakes of sugar-sweetened beverages, and lower intakes of fruits and nuts.
Dr Wendy Hall from KCL and senior author on the paper, said: ‘We know that major disruptions in sleep, such as shift work, can have a profound impact on your health. This is the first study to show that even small differences in sleep timings across the week seem to be linked to differences in gut bacterial 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 researchers found that three out of six microbiota species linked to ‘unfavourable’ health outcomes were more abundant in the social jet lag group. These microbes are associated with poor diet quality and are indicators of obesity and cardiometabolic health, and create markers in the blood related to higher levels of inflammation.
Dr Sarah Berry from King’s College London and chief scientist at ZOE added: ‘Maintaining regular sleep patterns, so when we go to bed and when we wake each day, is an easily adjustable lifestyle behaviour we can all do, that may impact your health via your gut microbiome for the better.’