TUESDAY, Jan. 1 , 2008 (HealthDay News) -- Children who get less than nine hours of sleep a night are more likely to be overweight or obese, new research shows.
Sleep-deprived kids also have more than a 3 percent increase in body fat on average compared to youngsters who sleep for more than nine hours nightly.
The researchers also reported that children's sleep patterns vary by season and day. Children sleep fewer hours in the summer and on weekends, according to the study.
Researchers at the University of Auckland in New Zealand studied the sleep patterns of 591 seven-year-old children using actigraphy -- a movement-based, noninvasive method used to study sleep-wake patterns and circadian rhythms. The children were assessed at birth, at one year of age, at three-and-a-half years and at seven years.
The team found that the children slept 10.1 hours on average. They slept fewer hours on weekend days than on weekdays, in the summer and when bedtime was set as after 9 p.m. They also slept fewer hours if they had no younger siblings.
In addition to increased weight and body fat, shorter sleep periods correlated with more emotional volatility, reported the research team.
"Sleep is important for health and well-being throughout life," said lead author Ed Mitchell in a prepared statement. "Few studies have objectively measured sleep duration. In this large study of sleep in seven-year-olds, there was considerable variation in duration of sleep. Sleep duration was 40 minutes longer in winter than summer and was 31 minutes longer on weekdays than on the weekend. Short sleep duration was associated with a threefold increased risk of the child being overweight or obese. This effect was independent of physical activity or television watching. Attention to sleep in childhood may be an important strategy to reduce the obesity epidemic."
The American Academy of Sleep Medicine recommends that children in preschool sleep between 11 and 13 hours a night and school-aged children between 10 and 11 hours of sleep a night.
The academy suggested that parents give their children an opportunity to get the recommended amount of sleep by keeping a consistent bedtime routine in a relaxed setting. Children may also sleep better if they have a parent to relate to before bed, instead of TV or video games. Food, drinks and medicines that contain caffeine are all enemies of sleep, according to the academy.
The study is published in the January issue of Sleep.
To learn more about healthy children and sleep, visit the American Academy of Pediatricians.