NEW DELHI — Night owls -- a person who is habitually active or wakeful at night -- tend to have a higher body mass index (BMI), larger waists, and more hidden body fat and thus are almost 50 per cent more likely to develop type 2 diabetes (T2D) than those who go to bed earlier, shows new research on Monday.
Previous studies have indicated that late chronotype -- people who prefer to go to bed late and wake up late -- live an unhealthy lifestyle, and are at higher risk of obesity and metabolic disorders including type 2 diabetes.
The new study showed that a late chronotype had a 46 per cent higher risk of developing diabetes, which suggests that the increased risk of T2D can't be explained by lifestyle alone.
"We believe that other mechanisms are also at play," said lead researcher Dr. Jeroen van der Velde, from Leiden University Medical Centre, in the Netherlands.
"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," van der Velde added.
To explore, the team studied the association between sleep timing, diabetes, and body fat distribution in more than 5,000 individuals who were divided into three groups: early chronotype (20 per cent), late chronotype (20 per cent), and intermediate chronotype (60 per cent).
The team measured all participants’ BMI and waist circumference, while visceral fat and liver fat were measured in 1,526 participants, using MRI scans and MR spectroscopy, respectively.
About 225 were diagnosed with diabetes after a follow-up of 6.6 years.
Late chronotypes were found to be at higher risk of developing diabetes, 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.
More visceral fat and liver fat were responsible for making people with a late chronotype to be at greater risk of developing type 2 diabetes, van der Velde said.
The findings will be presented at the Annual Meeting of the European Association for the Study of Diabetes (EASD) in Madrid, Spain (September 9-13).