Study: Late Bedtimes for Children Age 2-6 is Linked to Obesity

Bedtime – it’s something that most parents look forward to. Reading a story, tucking your little one in, and finally sitting down for an hour or two or relaxation. But, if your preschooler is getting to be too late, it can leave them at risk for future health problems.

A new study looked at bedtimes for children between age two and age six and found that children who routinely went to sleep after 9:00 p.m. had a greater body mass index, waist size, and tended to gain more body fat than children who shut their eyes earlier.

The commentary accompanying the study was written by Dr. Nicole Glaser, a pediatric endocrinologist at the University of California, Davis. She said
that while this doesn’t prove that late bedtimes lead to weight gain, it adds to the growing body of evidence that link childrens’ sleep habits to their weight.  

Glaser said, "At this point, I think it's clear that there is a relationship between [sleep quality and obesity risk]. The big question is whether the relationship is a causal one."

Other studies have shown that children with sleep problems – those who have trouble falling or staying asleep or get too little sleep – have higher rates of obesity.  

Senior researcher on this study, Dr. Claude Marcus, professor of pediatrics at the Karolinska Institute in Stockholm, Sweden said, "The causality is difficult to establish.”

He noted that sleep habits aren’t necessarily independent of other factors. Children who stay up late may have less restrictions put on them by parents in general. Additionally, because these children are awake longer hours, they may simply be eating more. And stress, which is linked to poor sleep habits, can lead to overeating.

Glaser discussed brain functionality as it relates to sleep. She said that there are areas of the brain that both manage appetite and regulate sleep-wake cycles, and that some of the same brain chemicals and hormones are involved in both.  

Glaser said that it’s possible that sleep problems may alter behavior, like physical activity during the day, or may change a child’s metabolism.

However, she noted that, “It’s equally possible that the association between sleep patterns and obesity simply reflects the fact that similar brain centers are involved in modulating both.”

The study involved 107 young children as part of an obesity project. Of those, 64 had obese or overweight parents, making them high risk for excessive weight gain.
For one week a wrist device was used to monitor sleep activity of the children between age two and age 6 and sleep activity was recorded.

Increase in BMI and waist size was found over the years for children who frequently fell asleep after 9:00 and that link was independent of total sleep times. The link was also present when researchers took into account factors like physical activity level, screen time, and parents’ education.  

For children of obese parents, the connection was more significant, showing that their waist size grew by an average of 1.4 inches more than children who were asleep before 9:00 p.m with average weight parents.

Again, this doesn’t mean that late bedtimes cause obesity but it does make those children more at-risk for it, whether it be due to physiology or lifestyle.

As researchers do further studies to determine the cause, the message for parents is that healthy sleep habits are important for the health of their children.
Glaser said, "An earlier bedtime for kids is absolutely a good idea.”

She added, "Parents can have some much-needed quiet time and time together to recharge the batteries, so they can have more energy for their kids the next day.”
"A well-organized life with good sleeping habits may be of importance, whether it is directly affecting weight or if it is a marker of living habits in general," Marcus said.

According to the American Academy of Sleep Medicine, each individual has different sleep needs, but generally recommends that toddlers sleep 11 to 14 hours per day including naps, and preschoolers age 3-5 should get 10 to 13 hours.

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