Jan. 24, 2011 -- Children who get too little sleep and have irregular school-day sleep schedules are more likely to be obese, especially if they don’t make up for lost sleep on the weekends, a new study finds.
When researchers monitored the sleep patterns of about 300 children between the ages of 4 and 10 for a week, they found that very few slept the recommended amount. The National Sleep Foundation recommends that preschoolers aged 3-5 sleep 11 to 13 hours daily and children aged 5-10 sleep 10 to 11 hours.
Most Kids Sleep 8 Hours
Most children slept about 8 hours, and school-day sleep patterns were not radically different for normal weight, overweight, and obese children.
But obese children did sleep less overall, their sleep schedules were more irregular, and they were less likely to experience “catch-up” sleep on the weekends, University of Chicago professor of pediatrics David Gozal, MD, tells WebMD.
Compared to children who slept about 9 hours a night, children who slept an average of 7 hours and had the most irregular sleep patterns had a fourfold greater risk of being obese, Gozal says.
Kids with irregular weekday sleep schedules who made up for lost sleep during the weekend were less likely to be obese than children who did not get the catch-up sleep.
The research was published today in the journal Pediatrics.
“Their risk was still higher than kids who got enough sleep and had regular sleep patterns, but it was less than when short sleep was combined with irregular sleep,” he says.
Poor Sleepers Had More Metabolic Risk
Although earlier studies have linked insufficient sleep and poor sleep habits to obesity in children, most have relied on parental recall to determine how much sleep kids were getting.
Gozal says parents tend to overestimate the amount of sleep their children get during the night by 60 to 90 minutes.
The study is the first to actually monitor sleep in children over the course of a week.
The children wore a wrist device called an Actiwatch, which is similar to a wristwatch but measures and records motion.
Study participants slept, on average, about eight hours a night, whether they were normal weight, overweight, or obese. But obese children slept less on weekends, suggesting that they were not making up for missed sleep during the week, Gozal says.
The researchers also took blood samples from about half of the children to measure metabolic and inflammatory risk factors for heart disease and diabetes such as glucose, insulin, cholesterol, and triglycerides.
Shorter overall sleep duration and irregular sleep were associated with a greater prevalence of these risk factors.
The findings do not prove that sleeping too little or having a poor sleep routine are direct contributors to obesity and the development of metabolic risk factors for disease.
Expert: Catching Up Easier for Older Kids
But Gozal says the evidence supporting the association continues to mount.
“There is very little respect for sleep in our society, and we think this needs to change,” he says.
Pediatrician and sleep researcher Julie Lumeng, MD, of the University of Michigan, agrees that the research on sleep and childhood obesity supports, but does not prove, a link between the two.
Lumeng’s own research, published in 2007, found that sixth graders who averaged less than 8 1/2 hours of sleep each night were almost twice as likely to be obese as sixth-graders who slept more than 9 1/2 hours.
She says for younger children, like the ones in the study, having a regular bedtime and a regular nightly routine may be particularly important.
She says although older children and teens may be able to catch up on lost sleep on weekends, younger children usually cannot do this.
“Teens can easily sleep until noon or even 1 if they have been up late the night before, but young children’s brains are not wired to allow them to do this,” she says. “If a 7-year-old stays up until midnight on a Saturday night, she is probably still going to wake up early the next day.”