Nighthawks at greater risk of developing T2D

The Netherlands Epidemiology of Obesity study presented at EASD 2024 shows a link between late chronotype and an increased risk of developing type 2 diabetes (T2D).

“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 [and this may be] why they are at higher risk of obesity and metabolic disorders including T2D,” noted lead study investigator Dr Jeroen van der Velde from Leiden University Medical Center in the Netherlands.

“However, lifestyle cannot fully explain the relation between late chronotype and metabolic disorders. In addition, while it is known that a late chronotype is associated with high BMI, it is unclear to what extent chronotype affects body fat distribution,” he continued. “We believe other mechanisms are also at play.”

Hence, van der Velde and colleagues set out to ascertain the correlation between late chronotype and waist circumference, visceral and liver fat, and the risk of T2D in a middle-aged population. They evaluated nearly 5,000 participants (mean age 56 years, 54 percent women, mean BMI 30 kg/m²) and calculated the midpoint of sleep (MPS) from participants’ typical bed and waking times.

The participants were then divided into three groups: early (the 20 percent with the earliest MPS [<2:30]), late (the 20 percent with the latest MPS [≥4:00]), and intermediate chronotype (the remaining 60 percent [2:30–4:00]). Visceral fat and liver fat were measured using MRI scan and MR spectroscopy, respectively (n=1,566). [EASD 2024, abstract 283]

A total of 219 incident cases of T2D were diagnosed during a median follow-up of 6.6 years.

After adjusting for age, sex, physical activity, smoking, alcohol intake, diet quality, sleep duration, and total body fat, late chronotypes had an increased risk of T2D than intermediate chronotypes (hazard ratio, 1.55, 95 percent confidence interval, 1.12–2.14). This finding implies that the increased T2D risk in late chronotypes cannot be attributed to lifestyle alone.

“A likely explanation is that the circadian rhythm or body clock in late chronotypes is out of sync with the [typical] work and social schedules … This can lead to circadian misalignment, which can lead to metabolic disturbances and, ultimately, T2D,” explained van der Velde.

Moreover, late chronotypes had a higher BMI (by 0.7 kg/m²), greater abdominal adiposity or larger waist circumference (by 1.9 cm), and more visceral (by 7 cm²), and liver fat (by 14 percent) than intermediate chronotypes.

“People with a late chronotype appear to be at greater risk of developing T2D than those with intermediate chronotype, possibly because of higher body fat including more visceral and liver fat,” said van der Velde.

Next step: Check on timing

Late chronotypes are likelier to eat until later in the evening, he said. “[Hence,] the next step is to study if those with a late chronotype improve in metabolic health when they change the timing of their lifestyle habits ... [T]here is growing evidence that time-restricted eating … may lead to metabolic benefits.”

For nighthawks, van der Velde recommended trying time-restricted eating or resisting late-night food cravings. “The evidence is not there yet, but in time, we aim to provide specific advice regarding the timing of lifestyle behaviour.”