MedicalResearch: What is the background for this study?
Dr. Nan Hee Kim: Many individuals in modern society experience a discrepancy between social and biological time. Especially during the work or school week, we are often forced to be awake against our preferred time. In addition, the increase of light, TV, computer and internet make people stay up late at night. However, night owls (evening persons) have been reported to have more health and behavioral problems than morning persons. Evening persons experience eating disorders, negative mood and insufficient sleep compared to morning persons. They initiate sleep later in the night but need to wake up earlier than their biologic morning due to social demands. There is abundant evidence that short sleep duration and insomnia are significant risk factors for obesity and diabetes. Therefore, we feel the necessity to reveal whether evening persons are associated with metabolic abnormalities in the general population.
MedicalResearch: What are the main findings?
Dr. Nan Hee Kim: In middle-aged adults, people who stayed up late had a 1.7-fold increased risk for type 2 diabetes and metabolic syndrome, and a 3.2-fold increase in risk for sarcopenia as compared with morning persons, independent of sleep duration and lifestyle. Evening persons were associated with reduced muscle mass in men and increased fat mass including visceral fat in women.
MedicalResearch: What should clinicians and patients take away from your report?
Dr. Nan Hee Kim: Many things of modern environment make people stay up late. In this study, we found that evening persons were associated with a higher prevalence of diabetes, metabolic syndrome and sarcopenia in middle-aged adults, independent of sleep duration and lifestyle. Evening persons had poor sleep quality and unhealthy behavior patterns such as smoking, lack of exercise and eating late at night, which possibly contribute to the adverse metabolic outcomes of them. Considering evening type is more prevalent in the younger age groups, these findings are important major health issue since they are at high risk for diabetes or metabolic syndrome in the relatively young age. Furthermore, this finding may become more severe due to the increasing social pressure.
MedicalResearch: What recommendations do you have for future research as a result of this study?
Dr. Nan Hee Kim: In the future, it remains to be seen whether young people with evening type will have the early development of metabolic disorders such as diabetes and metabolic syndrome compared with morning types, though a randomized prospective long-term follow-up study. And also, basic and genetic research will have to be performed to reveal the mechanism of adverse metabolic outcomes in evening persons.
MedicalResearch.com Interview with: Nan Hee Kim M.D., Ph.D., Professor (2015). Night Owls May Have Increased Risk of Metabolic Syndrome and Diabetes