Scimex: Night owls are more likely to develop diabetes, obesity, hypertension, high cholesterol, and decrease of muscle mass than early risers, even when they get the same amount of
sleep, according to a new study published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism.
The study examined the difference between night and morning
chronotypes, or a person's natural sleep-wake cycle. Staying awake later
at night is likely to cause sleep loss, poor sleep quality, and eating
at inappropriate times, which might eventually lead to metabolic change.
"Regardless of lifestyle, people who stayed up late faced a higher
risk of developing health problems like diabetes or reduced muscle mass
than those who were early risers," said one of the study's authors, Nan
Hee Kim, MD, PhD, of Korea University College of Medicine in Ansan,
Korea. "This could be caused by night owls' tendency to have poorer
sleep quality and to engage in unhealthy behaviors like smoking,
late-night eating and a sedentary lifestyle."
The study examined sleeping habits and metabolism in 1,620
participants in the population-based cohort Korean Genome Epidemiology
Study (KoGES). The study subjects were between the ages of 47 and 59.
Participants responded to questionnaires about their sleep-wake cycle,
sleep quality and lifestyle habits such as exercising. Researchers took
blood samples to assess participants' metabolic health. In addition, the
study subjects underwent DEXA scans to measure total body fat and lean
mass, and CT scans to measure abdominal visceral fat.
Based on the questionnaire results, 480 participants were classified
as morning chronotypes, and 95 were categorized as evening chronotypes.
The remaining participants had a sleep-wake cycle between the two
extremes.
Even though the evening chronotypes tended to be younger, they had
higher levels of body fat and triglycerides, or fats in the blood, than
morning chronotypes. Night owls also were more likely to have
sarcopenia, a condition where the body gradually loses muscle mass. Men
who were evening chronotypes were more likely have diabetes or
sarcopenia than early risers. Among women, night owls tended to have
more belly fat and a great risk of metabolic syndrome, a cluster of risk
facts that raise the risk of heart disease, stroke and diabetes.
"Considering many younger people are evening chronotypes, the
metabolic risk associated with their circadian preference is an
important health issue that needs to be addressed," Kim said.
Other authors of the study include: Ji Hee Yu, Jae Hee Ahn, Hyun Joo
Cho, Seung Ku Lee, Hye Jin Yoo, Ji A. Seo, Sin Gon Kim, Kyung Mook Choi,
Sei Hyun Baik, Dong Seop Choi and Chol Shin of Korea University College
of Medicine in Ansan, Korea; Chang-Ho Yun of Seoul National University
Bundang Hospital in Seongnam, Korea; and Sooyeon Suh of Sungshin Women's
University in Seoul, Korea.
The study, "Evening Chronotype Is Associated with Metabolic Disorders
and Body Composition in Middle-Aged Adults," was published online,
ahead of print.