Awesome news for parents of toddlers: a new study has found the ideal bedtime.
Early bedtimes don’t just stave off crankiness; they also prevent preschoolers from becoming teens with unhealthy BMIs.
“Earlier bedtimes were protective against obesity,” Sarah Anderson, an associate professor of epidemiology at Ohio State University and author of the study from the Journal of Pediatrics, told TODAY.
For a healthy weight as a teen, when should the tot be tucked in? At least by 8 p.m.
“Preschool-age children whose bedtimes are at 8 or before were half as likely to be obese 10 years later,” said Anderson.
Related: 4 ways to improve your child's bedtime routine
To understand the relationship between toddlers’ bedtime and obesity in adolescence, the researchers examined data from 977 children in the Study of Early Child Care and Youth Development, a longitudinal study examining child care and development.
Specifically, Anderson looked at what time parents reported putting their 4 ½-year-old children to bed; there was no data on wake time. Then, she examined the BMI of the children when they were 15 and compared it to their bedtimes. While bedtime doesn’t represent how much sleep children get, experts believe that the earlier children go to bed, the more likely they are to get extra sleep.
An association between earlier bedtimes for kids and healthier weight at age 15 emerged; later bedtimes were related to increased risk of obesity. Only 10 percent children who went to bed at 8 p.m. or earlier were obese, 16 percent of children who went to bed between 8 p.m. and 9 p.m. were obese, while 23 percent of children who went to bed at 9 p.m. and later were obese. This was the same for both boys and girls.
“What a difference an hour can make,” said Dr. Shalini Paruthi, co-director of the Sleep Medicine and Research Center at St. Luke’s Hospital in St. Louis, who wasn’t involved with the study. “The more sleep kids can get at night can lead to better outcomes in the long term.”
While it shows bedtimes have a moderate effect on teenage obesity rates, the study does have a limitation, said Dr. Sangeeta Chakravorty, director of the Pediatric Sleep Program of Children’s Hospital of Pittsburgh of UPMC.
“It doesn’t tell us much about the total sleep time that the child needs in order to prevent … obesity,” she said. Guidelines recommend toddlers receive nine-and-a-half to 11-and-a-half hours of sleep a night.
“However, it does say a lot about consistency and limit setting to develop good sleep habits.”
When parents set bedtime routines, their children often maintain such routines throughout life. What's more, people with healthy sleep habits often exercise and eat healthy, too.
It's important to note the study found a relationship, but not a causal one; there's no evidence that earlier bedtimes help people lose weight, for example. But Chakravorty said it reinforces what experts know about sleep and weight.
"Sleep and appetite and nutrition are very closely linked neurologically speaking because they are both biological drives. So disruption in either can affect the other," she said.
Related: 8 things we learned from a sleep expert about putting kids to bed
The study finds poor mothers, less educated mothers, and African-American and Hispanic mothers were more likely to have later bedtimes for their children. Anderson admitted she understands setting early bedtimes will often be a struggle for some. If a mom works late, for example, she might want to spend time with her children after she arrives home, delaying the bedtime.
That’s one of the reasons why Paruthi, a board member of the American Academy of Sleep Medicine, said establishing a consistent schedule might work better than trying to put a child down before a certain time.
“We recommend having bedtime routines even with newborns," she said. “We want more kids to develop more sleep habits that will stay with them into adulthood.”