Irregular sleep patterns may be linked to harmful bacteria in your gut, new research suggests.
The study is the first to find multiple associations between social jet lag – the shift in internal body clock when sleeping patterns change between workdays and free days – and diet quality, diet habits, inflammation and gut microbiome (bacteria) composition.
According to the findings, even a 90-minute difference in the midpoint of sleep – half-way between sleep time and wake-up time – can encourage microbiome that has negative associations with health.
Previous research has suggested that working shifts disrupts the body clock and can increase risk of weight gain, heart problems and diabetes.
However, according to researchers from King’s College London there is less awareness that the body’s biological rhythms can be affected by smaller inconsistencies in sleeping patterns.
This is due to people working regular hours waking early with an alarm clock on workdays compared to waking naturally on non-workdays.
Senior author Dr Wendy Hall from King’s College London, 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 seems 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."
First author Kate Bermingham, from King’s College London and senior nutrition scientist at ZOE, 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 unfavourable associations with your health."
Researchers suggest the composition of the microbes in the gut may negatively or positively affect health by producing toxins or beneficial products.
Specific species of microbes can correspond to an individual’s risk of long-term health conditions such as diabetes, heart disease and obesity.
The microbiome is influenced by what food someone eats, which makes the diversity of the gut adjustable.
Researchers assessed a group of 934 people from the ZOE Predict study, the largest ongoing nutritional study of its kind.
They looked at blood, stool and gut microbiome samples, as well as glucose measurements in people whose sleep was irregular compared to those who had a routine sleep schedule.
Unlike past research, the group consisted of mainly lean and healthy individuals with most of them getting more than seven hours sleep throughout the week.
The study, published in The European Journal of Nutrition, found that just a 90-minute difference in the timing of the midpoint of sleep is associated with differences in what the gut microbiome is made up of.
According to the findings, having social jet lag was associated with lower overall diet quality, higher intakes of sugar-sweetened beverages, and lower intakes of fruits and nuts.
This may directly influence the abundance of specific microbiota in the gut, researchers say.
Three out of the six microbiota species more abundant in the social jet lag group have what researchers describe as unfavourable associations with health.
They are linked with poor diet quality, indicators of obesity and cardiometabolic health, like heart attack, stroke, and diabetes, and markers in your blood related to higher levels of inflammation and cardiovascular risk.
Previous research has found social jet lag is associated with weight gain, chronic illness and mental fatigue.
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."
