Night owls may have a higher diabetes risk, independent of lifestyle factors

• Type 2 diabetes risk has been associated with late chronotype, or a tendency to go to sleep later.
• Previously it was assumed this was due to poorer habits of people with late chronotype, but new data presented at the Annual Meeting of the European Association for the Study of Diabetes has suggested this risk is independent of lifestyle factors.
• Late chronotype is associated with higher adiposity, which could be linked to a higher type 2 diabetes risk, but the reasons for this are unclear and could be due to a range of factors, according to researchers.

‘Night owls’ are at increased risk of type 2 diabetes, as well as higher adiposity, data presented at a conference has shown.

Previous research has shown the link between having a late chronotype, where you feel a need to go to bed later than usual, and type 2 diabetes . This latest research has shown that this link is independent of lifestyle factors, authors argue.

Previously, peer-reviewed research published in the Annals of Internal Medicin e showed that late chronotype was associated with poorer lifestyle factors, including being more likely to smoke and being less active. This latest, non peer-reviewed research presented at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Madrid, Spain, held 9-13 September 2024, suggests that the link exists independent of lifestyle factors.

Researchers from Leiden University Medical Center, Leiden, Netherlands presented their abstract to attendees, showing the independent link between chronotype and type 2 diabetes.

Higher amounts of body fat in late sleepers

The researchers analyzed data from 4,999 participants without type 2 diabetes from the Netherlands Epidemiology of Obesity study, of whom 54% were women. They determined the participants’ chronotypes based on the information they had given about when they went to sleep and when they got up and calculated using the midpoint of their sleep. Twenty percent of the cohort were identified as having a late chronotype.

They showed that the later the midpoint of sleep, the higher a person’s waist measurement was, as well as having higher amounts of fat on their waist and liver. Analysis showed that the people they identified as having a late chronotype were not only at a 55% increased risk of type 2 diabetes over a 6-year follow-up, but they also had a higher average BMI, a larger waist, and higher visceral and liver fat, than people with an intermediate chronotype.

The researchers adjusted these results for age, sex, education, total body fat, physical activity, diet quality, alcohol intake, smoking, and sleep quality and duration, showing that the relationship between type 2 diabetes and obesity was independent of these.

Interestingly the team found different results from expected when they chose to look at the risk for people who had early chronotypes, “From the literature, we expected early chronotypes to have a similar risk of developing type 2 diabetes as intermediate chronotypes,” says lead researcher Jeroen van der Velde , PhD, of Leiden University Medical Centre. “Our results showed a slightly higher risk but this was not statistically significant.”

The influence of chronotype on health

Van der Velde told Medical News Today that he had investigated the relationship between chronotype and type 2 diabetes as he and others did not believe that lifestyle could solely account for the differences in risk seen. The study had shown a more significant effect than expected.

“However, given the observational nature of our study, residual confounding may still have occurred. This means that despite our efforts to control for lifestyle variables such as diet and exercise, these factors may still impact the observed risk difference,” he said.

“We did not really know what to expect for the associations with waist circumference, visceral fat and liver. In late chronotypes we observed in particular a larger waist and more visceral fat, suggesting that abdominal obesity may play a role in the increased metabolic risk for late chronotypes.”
— Jeroen van der Velde

The study did not examine why later chronotype had resulted in this increased risk of type 2 diabetes, but the authors think that the circadian cycle may play a role.

“We believe that, in part, our result may be explained by circadian misalignment that may occur in people with a late chronotype. From other studies, we know that circadian misalignment may lead to metabolic disturbances. Our society’s current work- or social environment is more tailored toward people with an early or intermediate chronotype,” Van der Velde said.

“Another explanation may be that people with late chronotype also will eat until later in the evening. Some studies have shown that time-restricted eating, for instance, no more food intake after 6 PM may help to improve metabolic health. Also, the quality of food that is eaten later in the evening may be less healthy (e.g. snacks). We did adjust for overall diet quality in our study, but unfortunately, we did not measure timing of food intake,” he explained.

Circadian rhythm and social timings

Our circadian rhythm describes the natural oscillation that occurs over a 24-hour period in our bodies. Our internal clock tells us when to get up in the morning, when we might feel hungry, when we feel at our most energetic and when we need to go to sleep.

There is natural variation between people that has been observed for generations, hence the concept of ‘night owls’ and ‘early birds’.

Despite this there are certain timings that society adheres to, for example starting work at a certain time in the morning. This can be difficult for people with late chronotype to adapt to, as naturally, they would still be asleep then.

Maria Knobel, MD , and medical director of Medical Cert UK, who was not involved in the research, tol d Medical News Today:

“Our society is built around the rhythms of early chronotypes, leaving late chronotypes at a disadvantage. Early chronotypes naturally fit into the conventional work and school schedules, resulting in more consistent patterns for sleep, meals, and physical activity, all of which are beneficial for metabolic health.”

“On the other hand, late chronotypes are forced to wake up earlier than their bodies would prefer, leading to a cascade of negative health effects. This societal misalignment might be the root cause of what is perceived as dysregulation in late chronotypes,” she said.