Sleeping in on the weekend may help children fight obesity, a new study suggests.
Too little sleep puts kids at risk of obesity and other health conditions, but "catch-up" sleep on weekends and holidays can mitigate the effects of weekday sleep deprivation, researchers say.
Lead researcher Dr David Gozal, chair of paediatrics at Comer Children's Hospital at the University of Chicago said most children do not get enough sleep.
Gozal's team monitored the sleep patterns of 308 children for a week and compared their sleep patterns with their body mass index (BMI), which is a measurement that takes into account height and weight. The children, who were four to 10 years old, averaged eight hours of sleep a night.
"This is way lower than the recommended amount of sleep that kids should get, which is about 9.5 to 10 hours at this age," Gozal said.
Lack of sleep dangerous for kids
Among the children who got the recommended amount of sleep, the risk of obesity, diabetes and cardiovascular problems was nil, Gozal said.
"But, as the amount of sleep became shorter and the regularity of sleep became less organised, the risk for obesity increased," he said.
"Kids who had the shortest sleep and had a more disorganised sleep schedule had more than a fourfold increase in the risk of being obese," he noted.
These children also had increased risk for cardiovascular problems and pre-diabetes, Gozal said.
However, if these children consistently slept longer on weekends to compensate, the risk for obesity and metabolic problems was reduced to a 2.8-fold increase. "It did not normalise it. It's still a risk but not as much as keeping your crazy short sleep schedule even during weekends," Gozal said.
It is this combination of less sleep and irregular sleep that appears to result in metabolic problems, such as high blood sugar, Gozal said. The report is published in Pediatrics.
Not enough sleep and cravings
Gozal says that other studies have shown that inadequate sleep has biological effects, including high blood sugar and cravings for sweet and high-fat foods. Insufficient sleep also makes it harder to lose weight, he said.
"All this would suggest that sleep is an important regulator of metabolism," Gozal said. "If we abuse our sleep by not sleeping enough, then we are likely to pay the price by being heavy and being at risk for cardiovascular and all the other metabolic complications," he said.
Children are sleeping less for various reasons, Gozal said. Busy family schedules and electronic media - cell phones, computers and TV - interfere with healthy bedtime routines. The result is that sleep suffers, he said, noting that while bedtime can be extended, we still have to get up at the same time.
"Children should follow a regular [sleep] schedule," Gozal said. "Follow the rule of sleep and you will be happy," he urged.
Why sleep is important
Frederick J. Zimmerman, of the department of health services at the University of California Los Angeles, said the study largely confirms earlier research that found inadequate sleep is a risk factor for obesity among children.
The new research offers a "tantalising suggestion that sleep that is inadequate both in duration and in consistency may have adverse metabolic effects," he added. However, it does not explain why obesity and sleep are related, Zimmerman said.
"It could be that obesity causes disturbed sleep or that inadequate sleep increases the risk of obesity. It could also be that a third factor, such as nighttime television, may lead both to obesity and to poor sleep," he said.
Despite these uncertainties, the consensus is that parents should create an environment in which children can consistently get adequate, restful sleep, Zimmerman said.
"As difficult as it is for parents to consistently enforce early bedtimes, it may still be one of the easiest ways to promote happy, healthy children," he added.
So, watch the clock, these experts say. The study found that parents tend to overestimate the amount of sleep their kids get, usually by 60 to 90 minutes, Gozal said.
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