People who are more active at night – often referred to as night owls – have a higher risk of developing type 2 diabetes, according to a study.

Those who stay up late are more likely to smoke or have an unhealthy diet, researchers said, although they stressed the increased diabetes risk may not be down to lifestyle alone.

Night owls concerned about their diabetes risk should try not to eat late at night, they suggested.

The Dutch study, which will be presented at the annual meeting of the European Association for the Study of Diabetes (EASD) in Madrid, used data from the Netherlands Epidemiology of Obesity.

Researchers analysed sleep timing, waist circumference and the body mass index (BMI) of 5,026 people.

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

Of the group, 1,576 had MRI scans to measure visceral and liver fat, while electronic health records were used to check how people had type 2 diabetes.

Patients were categorised into three groups, or “chronotypes”, based on their sleep timing; late, early and intermediate.

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.”

The group was followed up for a median of 6.6 years, during which 225 patients were diagnosed with type 2 diabetes.

When adjusted for age, sex, total body fat and lifestyle factors such as exercise, diet and smoking, the study found people who preferred to stay up late had a 46% higher risk of type 2 diabetes than people in the intermediate group.

Dr van der Velde suggested there could be “other mechanisms also at play” outside of lifestyle.

“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,” he said.

“This can lead to circadian misalignment, which we know can lead to metabolic disturbances and ultimately type 2 diabetes.”

Night owls who are concerned about the increased risk of type 2 diabetes might want to... try to refrain from eating late in the evening

Researchers also found night owls tended to have a higher BMI, a larger waist circumference, more visceral fat and higher liver fat content.

Dr van der Velde added: “People with a late chronotype are probably more likely to eat until 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.

“The evidence isn’t there yet but, in time, we aim to provide specific advice regarding the timing of lifestyle behaviour.”

Another study being presented at the EASD meeting suggests patients on systemic steroids are also more likely to develop diabetes.

Researchers at the diabetes trials unit in the University of Oxford’s Radcliffe Department of Medicine looked at 451,606 adults without diabetes, who were admitted to hospital in Oxford between 2013 and 2023.

Some 17,258 were treated with systemic steroids such as prednisolone, hydrocortisone and dexamethasone while in hospital, most commonly for autoimmune and inflammatory diseases.

Of the group, 316 developed diabetes while in hospital.

Study leader Dr Rajna Golubic said the results “give clinical staff a better estimate of how likely new diabetes is to occur and could prompt doctors to plan clinical care more effectively to detect and manage new diabetes”.