Results of the study show that fewer hours of sleep is associated with greater increases in adolescent body mass index (BMI) for participants between 14 and 18-years-old.
The findings suggest that increasing sleep duration to 10 hours per day, especially for those in the upper half of the BMI distribution, could help to reduce the prevalence of adolescent obesity. Full results of the study are available online in the latest issue of Pediatrics.
Previous studies have shown that a correlation exists between short sleep and obesity, but until now few have been able to rule out other variables such as time spent watching television and being physically active. The new study observed over 1,000 Philadelphia-area high school students from their freshmen through senior high school years. At six month intervals, study participants were asked to report their sleep patterns. At the same intervals heights and weights were reported and BMIs were calculated. Study authors suggest the results could have far-reaching implications and aid in reducing the high levels of adolescent obesity in the United States.
"The psychosocial and physical consequences of adolescent obesity are well documented, yet the rate has more than tripled over the last four decades," says lead author Jonathan A. Mitchell, PhD, postdoctoral fellow in the Center for Clinical Epidemiology and Biostatistics at the Penn Medicine.
"What we found in following these adolescents is that each additional hour of sleep was associated with a reduced BMI for all participants, but the reduction was greater for those with higher BMIs. The study is further evidence to support that getting more sleep each night has substantial health benefits during this crucial developmental period."
Overall, researchers noted the strength of the association between sleep and BMI was weaker at the lower tail of the BMI distribution, compared to the upper tail.
Importantly, the relationship between sleep duration and BMI remained after adjusting for time spent in front of computer and television screens and being physically activity, leading to the conclusion that more sleep could contribute to the prevention of adolescent obesity, even if national screen time and physical activity guidelines are met.
Based on the results, the authors suggest that increasing sleep from 8 to 10 hours per day at age 18 could result in a 4 percent reduction in the number of adolescents with a BMI above 25 kg/m2.