MADRID — research presented at the annual meeting of the European Association for the Study of Diabetes suggested.
In the study, night owls were almost 50% more likely to develop T2D than those who went to sleep earlier.
“The magnitude of this risk was more than I expected, [although] residual confounding may have occurred,” said Jeroen van der Velde, PhD, Leiden University Medical Center in the Netherlands, who presented the study.
“Late chronotype has previously been associated with unhealthy lifestyle and overweight or obesity and, subsequently, cardiometabolic diseases,” he said in an interview. However, although the current study found that individuals with late chronotypes did indeed have larger waists and more visceral fat, “we (and others) believe that lifestyle cannot fully explain the relation between late chronotype and metabolic disorders.”
“In addition,” he noted, “previous studies that observed that late chronotype is associated with overweight or obesity mainly focused on body mass index [BMI]. However, BMI alone does not provide accurate information regarding fat distribution in the body. People with similar BMI may have different underlying fat distribution, and this may be more relevant than BMI for metabolic risk.”
The researchers examined associations between chronotype and BMI, waist circumference, visceral fat, liver fat, and the risk for T2D in a middle-aged population from the Netherlands Epidemiology of Obesity study. Among the 5026 participants, the mean age was 56 years, 54% were women, and mean BMI was 30.
Using data from the study, the study investigators calculated the midpoint of sleep (MPS) and divided participants into three chronotypes: Early MPS < 2:30 PM (20% of participants); intermediate MPS 2:30–4:00 PM (reference category; 60% of participants); and late MPS ≥ 4:00 PM (20% of participants). BMI and waist circumference were measured in all participants, and visceral fat and liver fat were measured in 1576 participants using MRI scans and MR spectroscopy, respectively.
During a median follow-up of 6.6 years, 225 participants were diagnosed with T2D. After adjustment for age, sex, education, physical activity, smoking, alcohol intake, diet quality, sleep quality and duration, and total body fat, participants with a late chronotype had a 46% increased risk for T2D.
Further, those with a late chronotype had 0.7 higher BMI, 1.9-cm larger waist circumference, 7 cm2 more visceral fat, and 14% more liver fat.
Body Clock Out of Sync?
“Late chronotype was associated with increased ectopic body fat and with an increased risk of T2D independent of lifestyle factors and is an emerging risk factor for metabolic diseases,” the researchers concluded.
“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,” Dr. van der Velde suggested. “This can lead to circadian misalignment, which we know can lead to metabolic disturbances and ultimately type 2 diabetes.”
Might trying to adjust chronotype earlier in life have an effect on risk?
“Chronotype, as measured via midpoint of sleep, does change a lot in the first 30 years or so in life,” he said. “After that it seems to stabilize. I suppose that if you adapt an intermediate or early chronotype around the age of 30 years, this will help to maintain an earlier chronotype later in life, although we cannot answer this from our study.”
Nevertheless, with respect to T2D risk, “chronotype is likely only part of the puzzle,” he noted.
“People with late chronotypes typically eat late in the evening, and this has also been associated with adverse metabolic effects. At this stage, we do not know if a person changes his/her chronotype that this will also lead to metabolic improvements. More research is needed before we can make recommendations regarding chronotype and timing of other lifestyle behaviors.”
Commenting on the study, Gianluca Iacobellis, MD, PhD, director of the University of Miami Hospital Diabetes Service, Coral Gables, Florida, said: “Interesting data. Altering the physiological circadian rhythm can affect the complex hormonal system — including cortisol, ghrelin, leptin, and serotonin — that regulates insulin sensitivity, glucose, and blood pressure control. The night owl may become more insulin resistant and therefore at higher risk of developing diabetes.”
Like Dr. van der Velde, he noted that “late sleep may be associated with night binging that can cause weight gain and ultimately obesity, further increasing the risk of diabetes.”
Dr. Iacobellis’s group recently showed that vital exhaustion, which is characterized by fatigue and loss of vigor, is associated with a higher cardiovascular risk for and markers of visceral adiposity.
“Abnormal circadian rhythms can be easily associated with vital exhaustion,” he said. Therefore, night owls with more visceral than peripheral fat accumulation might also be at higher cardiometabolic risk through that mechanism.
“However environmental factors and family history can play an important role too,” he added.
Regardless of the mechanisms involved, “preventive actions should be taken to educate teenagers and individuals at higher risk to have healthy sleep habits,” Dr. Iacobellis concluded.
No information regarding funding was provided; Dr. van der Velde and Dr. Iacobellis reported no conflicts of interest.
A version of this article first appeared on Medscape.com.