People who go to bed late, often called “night owls,” are about 50% more likely to develop type 2 diabetes than those who go to bed early.

They also have higher body mass indexes (BMIs), larger waistlines, and more hidden body fat, such as visceral and liver fat, which contribute to metabolic health problems.

The study findings, which are yet to be published, will be presented at the European Association for the Study of Diabetes (EASD) annual meeting in Madrid, Spain.

The study, led by Dr. Jeroen van der Velde of Leiden University Medical Center in the Netherlands, focused on the relationship between sleep timing, body fat distribution and diabetes risk.

While previous studies had shown that late sleepers were more likely to have unhealthy lifestyles, such as smoking or a poor diet, this research shows that lifestyle alone does not fully explain the increased risk of type 2 diabetes in night owls.

Type 2 diabetes is one of the most common non-communicable diseases in India. More than 100 million people in the country suffer from this disease.

It is a long-term condition in which the body does not use insulin (a hormone secreted in the pancreas) properly, causing blood sugar levels to rise. It is often associated with obesity, inactivity and poor diet.

The study analyzed data from more than 5,000 individuals as part of the Netherlands Epidemiology of Obesity study. The participants, who had an average age of 56, provided details about their sleep habits, which were used to classify them into early, intermediate, and late chronotype groups (natural sleep-wake patterns).

Chronotype groups categorize people based on their natural sleep-wake patterns and preferences. These include:

Early Chronology: Like to wake up early and sleep early.
Intermediate Chronology: Keep a balanced sleep schedule, neither sleep early nor late.
Late Chronotypes: Likes to stay up late and get up late.

These clusters reflect individual differences in internal body clocks and daily rhythms.

Their BMI, waist size and body fat levels were also measured, while MRI scans were used to assess visceral and liver fat in a subset of participants.

Over a 6.6-year follow-up study, 225 participants developed type 2 diabetes.

“We believe that other mechanisms are also at work,” says Dr. van der Velde. “A possible explanation is that the circadian rhythm or body clock in late chronotypes is out of sync with the work and social schedules adopted by society. This can lead to circadian misalignment, which we know can lead to metabolic disturbances and ultimately type 2 diabetes.”

Those with a late chronotype were found to have a 46% higher risk of developing type 2 diabetes than the intermediate group, even after adjusting for factors such as age, physical activity and sleep quality.

They also had higher BMIs, larger waistlines, and more visceral and liver fat.

Dr. van der Velde recommends lifestyle adjustments, such as avoiding late-night meals and time-restricted eating, as potential strategies to improve the metabolic health of night owls.

Further studies are ongoing to understand the effect of lifestyle timing on the risk of type 2 diabetes.