Preschoolers who were in bed by 8 p.m. were half as likely to be obese 10 years later as their peers who were still up after 9 p.m., researchers report in the Journal of Pediatrics.
“Encouraging kids to go to sleep early may be one way to prevent excess weight gain,” lead author Dr. Sarah Anderson at Ohio State University in Columbus told Reuters Health.
Excess weight in children has become a major health problem in the U.S. According to the Centers for Disease Control and Prevention, roughly 17 percent of children and adolescents – nearly 13 million kids -are obese.
Anderson and coauthors used data on 977 children who were born healthy in 1991 and who were tracked every year until they were 15.
When the children were 4 years old, on average, their mothers reported their usual weekday bedtimes.
Half the kids had bedtimes after 8 p.m. but before 9 p.m., one quarter went to bed at 8 p.m. or earlier, and another quarter went to bed after 9 p.m.
When the researchers looked at the kids’ weights at age 15, they found that preschoolers who went to bed before 8 p.m. were least likely to be obese as teens. The likelihood of obesity was greater for the kids who went to bed between 8 and 9 p.m., and greatest for those who stayed up past 9 p.m. when they were little.
The rates of adolescent obesity were 10 percent, 16 percent, and 23 percent, respectively, in the three groups.
The researchers factored in other possible influences on obesity risk, including socioeconomic status and mothers’ obesity. They also adjusted for “maternal sensitivity,” a measure of the quality of the mother-child relationship, such as whether mothers paid attention to their child’s emotional needs, how often they supported their child’s decisions and how often they let their child make decisions on their own.
“Turns out that maternal sensitivity didn’t have an effect,” said Anderson.
Not all households have the luxury of putting their kids to bed early, Anderson acknowledged. “If parents come home late from their jobs, it can be challenging to have a regular routine.”
Even so, she said, it’s important for parents to think about their child’s bedtime, “so they get enough sleep and can function at their best.”
The study doesn’t prove cause and effect, said Dr. Dennis Styne, who studies childhood obesity at the University of California, Davis and was not involved with the study.
Obesity also runs in families, and if parents are obese, their children are at a higher risk of becoming obese, he said.
“Parents can’t change their genes, but they can instill good habits in their children, like when they should go to sleep and what foods they should eat,” Styne said.