Night Owls Are More Likely to Develop Type 2 Diabetes

Night owls tend to have a higher body mass index (BMI), larger waists, and more hidden body fat, and are therefore 50% more likely to develop type 2 diabetes (T2D) than those who go to bed earlier, according to new research to be presented at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Madrid, Spain (9-13 September), has found.

Lead researcher Dr Jeroen van der Velde, of Leiden University Medical Centre, Leiden, Netherlands, said via a press release: “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 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. In addition, while it is known that a late chronotype is associated with high BMI, it isn’t clear to what extent chronotype affects body fat distribution.”

The researchers assessed the link between sleep timing, T2D and body fat distribution in more than 5,000 individuals (54% women), as part of the Netherlands Epidemiology of Obesity study, an ongoing study into the influence of body fat on disease.

Participants filled in a questionnaire their typical bed and waking times and from this midpoint of sleep (MPS) was calculated. Subsequently, the population of interest were divided into three groups: early chronotype (the 20% of participants with the earliest MPS), late chronotype (the 20% of participants with the latest MPS) and intermediate chronotype (the remaining 60% of participants).

After a  median of 6.6 years, 225 people were diagnosed with T2D. 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% higher risk of T2D.

“We believe that other mechanisms are also at play,” says Dr van der Velde.  “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.”