Young people who sleep less may be more likely to be overweight, especially if they spend less time in rapid eye movement (REM) sleep, according to a report released on August 4, 2008 in Archives of General Psychiatry, one of the JAMA/Archives journals.

The obesity epidemic in the United States is well recognized, and has been occurring even in children. According to the background information in the article, the obesity rate in children between 6 and 11 years old has more than tripled in the last 30 years, and about 17% of the adolescents in the population are classified as obese or overweight presently. Obesity is generally caused by an uneven caloric intake and energy use balance, but there are many factors that could potentially affect obesity that are not well understood. Previously, an association has been suggested between fewer hours of sleep and a higher body mass index (BMI) in both adults and children.

To investigate this relationship in children, Xianchen Liu, M.D., Ph.D., of the University of Pittsburgh School of Medicine Department of Psychiatry and Western Psychiatric Institute and Clinic of the University of Pittsburgh Medical Center, and colleagues studied a total 335 children between the ages of 7 and 17 years. The subjects were observed using polysomnography for three nights in a row. Once sleep time, time spent in REM sleep, the time it took to fall asleep and other variables were observed, they were compared to a BMI calculation made using weight and height.
 
The researchers found that 14.6% of participants (49 youths) were at risk for becoming overweight, while 13.4% (45 youths) were already overweight. Comparing these children with those who had normal weights, the higher weight children slept approximately 22 fewer minutes per night. Additionally, their sleep efficiency, defined as the percentage of time that the subject remained asleep, was lower, their REM sleep time was shorter, they had less REM activity even in REM sleep, and took longer to reach their first REM sleep periods.

In all, one hour less of total sleep was associated with twice the risk of being overweight. Having one hour less of REM sleep was associated with three times the risk.

The authors note that there are many possible explanations for this association: "Although the precise mechanisms are currently under investigation, the association between short sleep duration and overweight may be attributed to the interaction of behavioral and biological changes as a result of sleep deprivation." For one, hormone levels may fluctuate differently when someone experiences loss of sleep, which could affect hunger. Additionally, the fatigue associated with sleep loss could lead to fatigue which reduces the amount of exercise experienced, thereby reducing the energy expenditure of the person.

The authors conclude that by improving sleep in this age group, some of the obesity experienced in this age group might be mitigated. "Given the fact that the prevalence of overweight among children and adolescents continues to increase and chronic sleep insufficiency becomes more prevalent in modern society, family- and school-based sleep interventions that aim to enhance sleep hygiene and increase sleep duration may have important public health implications for the prevention and intervention of obesity and type 2 diabetes in children," they say.  "Furthermore, our results demonstrate an important relationship between REM sleep and high BMI and obesity, suggesting that the short sleep"obesity association may be attributed to reduced REM sleep time and decreased activity during REM sleep."

Rapid Eye Movement Sleep in Relation to Overweight in Children and Adolescents
Xianchen Liu, MD, PhD; Erika E. Forbes, PhD; Neal D. Ryan, MD; Dana Rofey, PhD; Tamara S. Hannon, MD; Ronald E. Dahl, MD
Arch Gen Psychiatry. 2008;65(8):924-932.
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Anna Sophia McKenney

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