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, say researchers from the University of California, Los Angeles.
The findings 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. 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 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.
There are a number of theories why short sleep in early life might be a risk factor for excess weight gain.
For one, kids who don't get enough sleep could be too tired to engage in the amount of activity that they need. As well, 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.
These 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: Archives of Pediatrics and Adolescent Medicine, September 2010.
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