People who go to bed late are more likely to gain weight, according to a recent study.
Researchers from the University of California, Berkeley found that going to bed during the workweek each additional hour later is associated with a 2.1 points increase in body mass index (BMI), Sydney Morning Herald reported.
"The results are important because they highlight adolescent bedtimes, not just total sleep time, as a potential target for weight management concurrently and in the transition to adulthood," Lauren Asarnow, first author of the study and a doctoral candidate, said in a statement.
For the study, researchers collected and analyzed data from more than 3,000 adolescents between 1994 and 2009. Sleep and circadian variables were determined via self-reported measures at all three waves. Investigators measured height and weight at each wave, from which BMI was calculated.
Based on their analysis, researchers also found that the relationship between bedtime and BMI was not significantly changed or moderated by total sleep time, exercise frequency or screen time.
Researchers said this is the first study to look at the longitudinal relationship between bedtimes and BMI in any age group in an observational study.
"Conceivably, if you're going to bed an hour later, over time you could be shifting BMI categories from normal to overweight," Asarnow told The Daily Times Gazette. "So even a two-point increase could be clinically significant."
The American Academy of Sleep Medicine recommends that adolescents get a little more than nine hours of nightly sleep for optimal health and daytime alertness during the critical transition from childhood to adulthood.
The findings are detailed in the October issue of the journal Sleep.
