June 2020 Update:
Dr. Do wins the 2020 Rothman Epidemiology Prize for this article that has been selected as the best paper published in the journal Epidemiology in 2019.
View the announcement of the editors and editorial board of Epidemiology and our news post.
November 2019 Update:
Paper published: Do, Young Kyung. "Causal Effect of Sleep Duration on Body Weight in Adolescents: A Population-based Study Using a Natural Experiment." Epidemiology 30, no. 6 (2019): 876-884.
Despite a large number of observational studies consistently reporting the association between shorter sleep duration and higher body weight, causality has yet to be established at a population level. This study aims to estimate the population-level causal effect of sleep duration on adolescent body weight, using an instrumental variable (IV) approach that exploits a unique natural experiment in the context of South Korea’s highly competitive secondary education. In March 2011, amid growing concerns over the negative consequences of late-night tuition at private tutoring institutes (hagwon), authorities in 3 of the 16 administrative regions in South Korea decreed adjusting the closing hours of hagwon to 10 p.m. This policy change caused a substantial and plausibly exogenous variation in the sleep duration of the “marginal student,” whose sleep duration is most likely to be affected by the policy. The IV estimation results on a sample of general high school 10th- and 11th-graders in the 2009−2012 Korea Youth Risk Behavior Web-based Survey show that a 1-hour increase in sleep duration led to a 0.56 kg/m2 reduction in body mass index, or a 4.3 percentage-point decrease in overweight/obesity. Short sleep duration among adolescents may be an important contributor to increased body weight at the population level.