Sleep is very important for the overall health of our children. Poor childhood sleep has a strong association with childhood obesity, particularly when it comes to sleep duration.
Here's what we know: Preschoolers ages 3 to 5 should get between 10 and 13 hours of sleep. School-aged children should get between nine and 11 hours of sleep. Teenagers should get between eight and 10 hours of sleep.
What is less clear, however, is when our children should be going to bed.
A study published in The Journal of Pediatrics set out to determine whether preschoolers with earlier bedtimes had a lower risk for becoming obese in their teenage years.
Researchers analyzed data from 977 children who were born in 1991. Between 1995 and 1996 (when the children were aged between four and five), mothers reported their child's typical bedtime. When the children reached an average age of 15, their height and weight was measured to determine their body mass index (BMI).
The study revealed that:
- 25 percent of preschoolers went to bed by 8 p.m.
- 50 percent of preschoolers went to bed between 8 p.m. and 9 p.m.
- 25 percent of preschoolers went to bed after 9 p.m.
Researchers also found the prevalence of teenage obesity in these children to be:
- 10 percent in those who went to bed by 8 p.m.
- 16 percent in those who went to bed between 8 p.m. and 9 p.m.
- 23 percent in those who went to bed after 9 p.m.
After adjusting for age, sex, ethnicity, birth weight, maternal education, maternal obesity, and maternal sensitivity, the study found that preschoolers who went to bed by 8 p.m. were half as likely to become obese in adolescence compared to preschoolers who went to bed after 8 p.m.
Interestingly, researchers found that late bedtimes were not associated with a child's gender, birth weight, or maternal obesity. However, researchers did find that children who were not white, who were born to less-educated mothers or who lived in lower-income households were far more likely to have a late bedtime when at preschool age.
Why are earlier bedtimes for children better than later bedtimes?
Perhaps the discovery that earlier bedtimes are beneficial to the health of our children shouldn't come as too much of a surprise. After all, previous studies have also associated earlier bedtimes with fewer behavioral difficulties and later bedtimes with more attention difficulties and even aggression.
First, it's important to note that this was an observational study. It did not (and cannot) establish causality. In other words, this study does not prove that early bedtimes cause obesity in adolescence. It simply found an association that requires further investigation and study.
The hour at which children go to bed has the biggest effect on how much sleep they get; as parents, we have far less control over wake times than we do bed times. Therefore, children who go to bed later at night are more likely to get less sleep than those who go to bed earlier.
It's this reduction in total sleep time that may be the reason for the adverse health risks, such as obesity, in later life.
Although earlier bedtimes don't guarantee longer sleep durations, when combined with a regular bedtime routine (and limited exposure to artificial light at night) they do make it more likely that a child will get the sleep they need on a regular basis.
Martin is the creator of Insomnia Land’s free insomnia sleep training_ course. His online course uses cognitive behavioral therapy for insomnia techniques to help participants fall asleep and stay asleep. More than 4,000 insomniacs have completed his course and 97 percent of graduates say they would recommend it to a friend._