NEW YORK (Reuters Health) - Young children who don't get enough sleep may be at greater risk of becoming overweight or obese later on, new research shows.
Children four years old and younger who logged less than 10 hours of sleep a night were nearly twice as likely to be overweight or obese five years later, Dr. Janice F. Bell of the University of Washington in Seattle and Dr. Frederick J. Zimmerman of the University of California, Los Angeles, report in the September issue of Archives of Pediatrics and Adolescent Medicine.
The findings, Bell told Reuters Health, suggest that early childhood could be a "critical window" when nighttime sleep helps determine a child's future weight status.
According to the National Sleep Foundation, toddlers (1 to 3 years old) should sleep for 12 to 14 hours a night; preschoolers (3 to 5 years old) should sleep 11 to 13 hours; 5- to 10-year-olds should get 10 to 11 hours; and teens should get 8.5 to 9.25 hours of sleep nightly.
Several studies have linked short sleep to excess weight in children and teens, Bell and Zimmerman note in their report. But many of these studies have been cross-sectional, meaning they looked at a single point in time, which makes it difficult to determine whether not getting adequate sleep caused a child to become obese, or vice versa.
To address this issue, the researchers looked at the relationship between sleep and weight in 1,930 children from 0 to 13 years old who participated in a survey in 1997 and again five years later in 2002.
For children who were four years old or younger at the time of the first survey, sleeping for less than 10 hours a night was associated with nearly a twofold increased risk of being overweight or obese at the second survey, the researchers found.
For older children (age 5 to 13), sleep time at the first survey was not associated with weight status at the second survey; however, current short sleep time was associated with increased odds of a shift from normal weight to overweight status or from overweight or obese status at follow up.
These findings, say the authors, suggest that there is a critical time period prior to age five when adequate nightly sleep may be important in terms of a healthy weight later on.
The study couldn't show why short sleep in early life might be a risk factor for excess weight gain, Bell said, although there are a number of theories.
For one, "it might be that kids who don't get enough sleep are a little bit too tired to engage in the amount of activity that they need," the researcher said. For another, being up longer means more opportunities to eat. Finally, there's evidence that adults who don't get enough sleep have altered levels of the appetite- and hunger-related hormones leptin and ghrelin, and the same could be true in children, Bell said.
She and her colleagues now plan to investigate how much sleep American children are actually getting. While there's plenty of information out there on how much sleep kids should get, Bell noted, there's very little on children's real-life sleeping patterns.
No matter what, she added, the findings suggest that making sure children are getting enough sleep could be a new way to help fight overweight and obesity, along with promoting a healthy diet and physical activity.
SOURCE: http://link.reuters.com/den32p Archives of Pediatrics and Adolescent Medicine, September 2010.
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