Short REM sleep linked to overweight in kids.

Shortened sleep duration, particularly shortened REM sleep, is associated with overweight in children and adolescents, according to a recent report.

Given the high prevalence of both overweight and sleep deprivation 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," said Dr. Xianchen Liu of Western Psychiatric Institute and Clinic, Pittsburgh, and associates.

The researchers investigated the possible link between short sleep duration and overweight using data from a study of pediatric affective disorders in which 335 children and adolescents underwent 3 consecutive nights of polysomnography. The subjects were aged 7-17 years (mean age 11 years), 45 (13%) were overweight, and 15% were at risk for overweight.

A total of 166 of these subjects had internalizing disorders (major depressive disorder or anxiety disorder), 86 had no mood disorder but were at high risk because of family history, and 83 were healthy controls with no personal or family history of psychiatric disorder.

Overweight subjects slept approximately 22 minutes less than normal-weight children and had significantly less REM sleep time, a longer interval before REM sleep commenced (longer REM latency), and less REM activity. Reduced REM time was significantly associated with overweight in all three groups of subjects, regardless of the presence of psychiatric disorders (Arch. Gen. Psychiatry 2008;65:924-32).

Every hour of shorter sleep time was associated with a doubling of the risk of overweight, and every hour of shorter REM sleep time was associated with a tripling of this risk, they noted. "'This represents the first study to report specifically that REM sleep seems to be the stage most strongly associated with childhood overweight."

The mechanism underlying this link is not yet known. However, sleep loss is known to cause metabolic and endocrine changes such as decreased leptin levels, increased ghrelin levels, and higher rates of insulin resistance. And some reports have linked sleep loss with increased appetite and a preference for calorie-rich foods.

In addition, sleep loss leads to extra wake time, which means increased opportunity for eating in any given 24-hour period. It also increases fatigue and daytime sleepiness, which could in turn decrease physical activity. Finally, tiredness and irritability may interfere with inhibitory control, resulting in "less effective avoidance of unhealthy eating," Dr. Liu and associates said.

Because this study included children with internalizing disorders, the question of whether the results can be extrapolated to the general population needs further research, they said. But "in the current study, we did not fred significant differences in REM sleep time and REM activity between children with and without internalizing disorders," suggesting "that the REM sleep--overweight association may exist independent of psychiatric diagnosis.'"

Although they controlled for effects of age, sex, ethnicity, socioeconomic status, pubertal status, and psychiatric diagnosis, they did not control for some other important variables, such as sleep-disordered breathing, food intake, daily activity, family history of obesity, and parental body mass index.

BY MARY ANN MOON

Contributing Writer