Night owls (late chronotypes)

Night owls, or individuals with late sleep patterns (known as late chronotypes), may face a higher risk of developing type 2 diabetes (T2D),  even beyond the effects of an unhealthy lifestyle. Research presented at the European Association for the Study of Diabetes (EASD) 2024 Annual Meeting found that night owls were nearly 50% more likely to develop T2D compared to early risers.

Dr. Jeroen van der Velde, from Leiden University Medical Center in the Netherlands, who led the study, said, "The increased risk was larger than anticipated, although other factors might have influenced the results."

Previous studies have linked late chronotypes with poor lifestyle habits, obesity, and cardiometabolic diseases. This study confirmed that night owls tend to have larger waist sizes and more visceral fat, but Dr. van der Velde emphasized that lifestyle alone doesn't fully explain the connection between late chronotype and metabolic disorders.

Moreover, earlier studies often focused only on body mass index (BMI), which doesn't provide a complete picture of fat distribution. People with the same BMI may have different fat distribution, which may play a more significant role in metabolic risk.

The researchers analyzed data from the Netherlands Epidemiology of Obesity study, focusing on the relationship between chronotype, BMI, waist size, visceral fat, liver fat, and T2D risk in a middle-aged group. The study included over 5,000 participants with an average age of 56 years. Of the participants, 54% were women, and the average BMI was 30. Chronotype was determined using the midpoint of sleep, and participants were divided into three groups: early, intermediate, and late sleepers. MRI scans and spectroscopy were used to measure visceral and liver fat.

After a median follow-up of 6.6 years, 225 participants were diagnosed with T2D. Even after adjusting for lifestyle factors like diet, physical activity, and sleep quality, late chronotypes had a 46% increased risk of developing T2D. They also had higher BMI, larger waist sizes, and more visceral and liver fat than their earlier-sleeping counterparts.

The researchers concluded that a misaligned body clock in night owls may contribute to metabolic issues and increase the risk of T2D. Dr. van der Velde explained that night owls' circadian rhythms may not align with societal schedules, leading to metabolic disturbances.

While chronotype tends to change during the first 30 years of life, it stabilizes afterward. Dr. van der Velde suggested that adopting an earlier sleep pattern before the age of 30 may help maintain a healthier chronotype later in life, although this wasn't directly addressed by the study.

Dr. Gianluca Iacobellis, director of the University of Miami Hospital Diabetes Service, commented that disrupting circadian rhythms can impact hormone systems that regulate insulin sensitivity and glucose control, increasing the risk of diabetes. Night owls may also engage in late-night eating, which contributes to weight gain and obesity, further heightening the risk of diabetes.

Lacobellis noted that vital exhaustion, a condition marked by extreme fatigue, has been linked to higher cardiovascular risk and more visceral fat, which could further increase metabolic risks in night owls. He emphasized the importance of educating people, particularly teenagers and those at higher risk, about healthy sleep habits to prevent these issues.