Night owls at greater risk of Type 2 diabetes – but there’s something you can do to help
Night owls are more likely to develop Type 2 diabetes - and it is not just because they have less healthy lifestyles, research suggests.
The study of more than 5,000 adults examined the association between sleep timing, diabetes and body fat distribution.
Researchers found that those who went to bed late had a higher body mass index (BMI), larger waists and were almost 50 per cent more likely to develop Type 2 diabetes.
Previous studies have found links between late nights and Type 2 diabetes, but these have often been explained by unhealthier habits among those who stay up late, such as junk food consumption.
However, the new study by researchers in the Netherlands suggests that lifestyle cannot fully explain the links.
Researchers said that the disruption to the body clock - putting it “out of sync” with work and social schedules of society, could cause “circadian misalignment” which adversely affects metabolic health.
They suggested that night owls might benefit from either going to bed earlier, or having their last meal of the day sooner.
Lead researcher Dr Jeroen van der Velde, of Leiden University Medical Centre, in the Netherlands, said: “Previous studies have indicated that a late chronotype – preferring to go to bed late and wake up later – is associated with an unhealthy lifestyle.
“Late chronotypes are more likely to smoke or have an unhealthy diet, for example, and it has been suggested this is why they are at higher risk of obesity and metabolic disorders including Type 2 diabetes.
“However, we believe that lifestyle cannot fully explain the relationship between a late chronotype and metabolic disorders.”
More deadly visceral fat
The new study found night owls had more visceral fat - which is more deadly, as it surrounds the organs - and larger waistlines, which also carry higher health risks.
The study, which tracked participants for almost seven years, involved adults with an average age of 56, and a BMI of 30 kg/m2 - putting them on the edge of obesity.
After filling in questionnaires about their sleep habits, participants were then divided into three groups: early birds, night owls and those in between.
Waist circumference and BMI were measured in all participants. Visceral fat and liver fat were measured in 1,526 participants, using MRI scans and MR spectroscopy, respectively.
The participants were followed-up for a median of 6.6 years, during which 225 were diagnosed with Type 2 diabetes.
The results, which were adjusted for age, sex, education, total body fat and a range of lifestyle factors (physical activity, diet quality, alcohol intake, smoking and sleep quality and duration), showed that compared with an intermediate chronotype, participants with a late chronotype had a 46 per cent higher risk of Type 2 diabetes.
Researchers said this suggests that the increased risk of Type 2 diabetes in those who were late to bed could not be explained by lifestyle alone.
‘Body clock is out of sync’
Dr van der Velde said: “A likely explanation is that the circadian rhythm or body clock in late chronotypes is out of sync with the work and social schedules followed by society. This can lead to circadian misalignment, which we know can lead to metabolic disturbances and ultimately Type 2 diabetes.”
The results also showed that late chronotypes had a 0.7 kg/m2 higher BMI, 1.9 cm larger waist circumference, 7 cm2 more visceral fat and 14 per cent higher liver fat content, compared with those with an intermediate chronotype.
Dr van der Velde said: “People with a late chronotype appear to be at greater risk of developing Type 2 diabetes compared to those with intermediate chronotype, possibly because of higher body fat including more visceral fat and liver fat.”
Go to bed earlier
Future research will examine whether improvements in metabolic health can be made if night owls are persuaded to go to bed earlier, or to eat their last meal of the day sooner.
Dr van der Velde said: “People with a late chronotype are probably more likely to eat later in the evening”.
“While we did not measure this in our study, there is growing evidence that time-restricted eating, not eating anything after a certain time, such as 6pm, may lead to metabolic benefits.
“Night owls who are concerned about the increased risk of Type 2 diabetes might want to try this or, at least, try to refrain from eating late in the evening,” he said.
Blood sugar levels
Dr Lucy Chambers, who is head of research communications at Diabetes UK, said: “This study is consistent with previous research showing that ‘night owls’ have a higher risk of developing Type 2 diabetes and that this is linked to going to sleep late rather than getting insufficient sleep.
“The study also found that ‘night owls’ tend to have larger amounts of harmful internal fat in the liver and pancreas – organs that keep blood sugar levels in check – but we don’t yet know why this is or have any evidence that going to bed earlier can reduce Type 2 diabetes risk.
“It’s important to remember that Type 2 diabetes is a complex condition and the chances of developing it depend on a mix of biological, genetic and environmental factors.
“So while strategies to change sleep habits might help some people to reduce their risk of Type 2 diabetes, they are never going to be a ‘silver bullet’ for everyone at risk.”
