Later bedtimes in adolescent and adult years has been linked with an increase in body mass index (BMI). Body mass index uses age, height and weight to estimate body fat percentage. A high BMI reflects being overweight or obese which is associated with health complications.

By using results from a sample of over 3,000 individuals, researchers found a correlation between late bedtimes and high BMI over time. Total sleep time, exercise and time spent watching TV did not affect this correlation.

Lauren Asarnow from the University of California said, “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.”

The data came from three waves of the National Longitudinal Study of Adolescent Health, which studied 3,342 adolescents between 1994 and 2009. Circadian cycles and sleep were self-reported and height and weight were measured by researchers to calculate BMI.

This is the first noted study to examine long term sleeps effect on BMI.

Adolescents should get just over nine hours of sleep a night for optimal health, as recommended by the American Academy of Sleep Medicine. This amount of sleep aids with alertness and assists with changes from adolescence to adulthood.

The findings were published in the journal Sleep.

Sources:

http://www.eurekalert.org/pub_releases/2015-10

http://www.cdc.gov/healthyweight/assessing/bmi