- A new study found a connection between later bedtimes for children under six and increased risk of obesity.
- The study, conducted on 107 Swedish children, found that going to bed after 9 p.m. was a predictor of higher Body Mass Index.
- But before parents rush to put their kids to bed an hour earlier, they should know there are many factors beyond bedtime that could've influenced this finding, from increased screentime to diet to unhealthy diet.
- Visit Insider's homepage for more stories.
A new study found later bedtimes may increased the risk of obesity for young kids.
The study was conducted on 107 Swedish children from an obesity prevention project, 64% of whom had parents who were overweight or obese.
The children who went to bed later had a higher waist circumference and Body Mass Index by the end of the four-year long study. The study found that the amount of hours the children slept didn't matter — it was going to sleep after 9 p.m. that was associated with a higher risk of obesity.
"The late sleep time may reflect the lack of routine in children's daily life, and they may be more exposed to unhealthy lifestyle, which is related to both sleep and obesity," study author Julia Xiu told Insider. "Children who slept later may also have more opportunity to eat."
Flickr/kate hiscock
There have been previous studies analyzing the way sleep habits intersected with obesity risks, but many of them relied on self-reported sleep data. This study used sleep trackers to get objective sleep data from the children.
From ages one to six, researchers tracked each child's sleep for seven consecutive days, via a sleep tracker worn on the wrist. At each visit, researchers also took each child's height, weight and waist circumference measurements.
This study was part of the Early Stockholm Obesity Prevention Project, a larger study which recruited 238 families who were were visiting a local health clinic for their child's eight-month check-up. Though previous research found that parental obesity was a predictor of childhood obesity, this study found a child's sleep habits (which seemed to impact their weight) had nothing to do with their parents' health.
"Since it is an observational study, no causation can be drawn," Xiu said. So before parents rush to get their kids in bed at 8 p.m., they should remember that this study just found an association between late bedtimes and increased obesity rates. It may simply be that kids that stay up later have different habits which impact their weight.
A regular bedtime is good for children, but that varies based on culture
Research shows that a regular bedtime is better for growth and overall health, but when those children go to bed varies based on where in the world they live.
According to one study, children aged zero to three in Australia and New Zealand have the earliest bedtimes, heading to bed between 7:28 and 7:55 p.m., while children of that age in Hong Kong and India go to bed the latest, between 10:11 p.m. and 10:17 p.m.
In a commentary co-published with the research, Dr. Nicole Glaser and Dr. Dennis Styne, two pediatric endocrinologists at UC Davis Health, said the higher risk of obesity may be due to a number of other influences, from "excess screen time, inadequate exercise, or less vigilance overall about health habits on the part of the family."
Dr. Veronica Johnson, a pediatric obesity medicine specialist at UTHealth in Houston, who was not involved in the study, told Insider one limitation of the study is the study authors only evaluated sleep for seven consecutive days. "That doesn't show a full depiction of how sleep changes over time," she said.
Another limitation of the study was the sample size. The 107 children were all Swedish, and mostly Caucasian. "Compared to kids back in the US, I don't know how applicable these results are," she said. "Here, African American girls and Hispanic boys are more likely to show signs of obesity in adolescence."
That said, Johnson told Insider: "It would be worthwhile to advise kids to get a regular sleep schedule." The American Academy of Pediatrics recommends that children sleep between 11 to 13 hours a night.
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