Does sleeping late keep you slim?

sleeping childIs it possible that children who sleep in on the weekends and holidays are less likely to be overweight than their sleep-deprived counterparts? A recent study suggests as much. But Children’s Hospital Boston sleep specialist Dennis Rosen, MD, says that the study’s findings are problematic. Here, he explains why letting your child sleep in isn’t such a good idea.

by Dennis Rosen, MD

The connection between insufficient sleep and overweight and obesity is well recognized and has been demonstrated in multiple studies  over the last several years. In the November 2009 issue of Pediatrics, researchers report the results of a study conducted in Hong Kong in which they looked at whether differences in sleeping patterns that allowed school-age children to “catch up” on the sleep deficit acquired during the school week had an effect on their becoming overweight or obese.

They  conducted their study by reviewing questionnaires completed by the parents of 5,185 children between the ages of 5 and 15 in which the parents were asked to comment on what times their children usually went to bed and got up on weekdays, weekends and vacation during the preceding year. The investigators found that children who slept less than eight hours a night during the week and did not compensate for their sleep deprivation by sleeping  late on weekends or vacation were significantly more likely to be overweight than those who did.

However, there are many problems with this study. One is that the wide age range of the children: 5-year-olds have quite different sleep needs and patterns than 15-year-olds. Another is the fact that the data collected was based on a recollection of the child’s sleep patterns for an entire year, generating what is known as “recall bias. The number of children in the “non-compensated groups” is very small; 38  did not sleep in on weekends and 29  did not sleep in on vacations—and each is less than 1 percent of the entire study—making drawing meaningful conclusions from this study difficult. In fact, when looking at the data, one sees that the overweight and obese children slept only six minutes less on school nights, nine minutes less on weekends and 10 minutes on vacation than their non-overweight counterparts.

For all these reasons, it is difficult to accept the authors’ conclusions that children should be allowed to sleep in late on weekends as a means to prevent them from becoming overweight. In fact, there are compelling reasons not to adopt such a strategy. The two main forces that drive our sleep are the sleep deficit, which builds up the longer we remain awake, and the internal circadian clock. When the internal circadian clock is synchronized with the external clock, we start to feel sleepy around our usual bedtime and wakeful around our usual wake up time (provided, of course, that we have gotten enough sleep).

However, it is relatively easy to desynchronize the internal from the external clock by shifting sleep onset and wake-up times, exposure to bright light in the evening and/or the morning and the consumption of melatonin. This is especially true for adolescents, who have a natural tendency to “push back” their internal clocks. When the clocks become desynchronized, it becomes quite difficult to fall asleep and to wake up at the appropriate “external clock” times, as anyone who has become jetlagged knows all too well.

The last thing a child who is not getting enough sleep during the week because she or he is getting to bed too late needs is to sleep in two, three or four hours late on the weekend. While allowing the child to “catch up” on some of the lost sleep, it can also decouple the two clocks and make it difficult for the child to get out of bed on Monday morning in time for school and to really get going before the school day is half gone.

Yes, getting enough sleep is very important, not just for controlling body weight, but for a whole host of other important reasons as well, including good cognitive function, development, school performance and behavior. But a better solution would be to establish a schedule which gets the child to bed regularly at an hour that allows for an age-appropriate amount of sleep, and maintains a regular wake-up time on weekdays and weekends. One should also minimize exposure to bright light in the evening, eliminate caffeine at least eight hours before bedtime and remove distractions such as TV, computers, video games, cell phones media players and pets from the bedroom.

Doing all of the above will increase the likelihood of the child getting an adequate amount of sleep, with all the attendant benefits, and without turning weekday mornings into a nightmare for child and parents alike.

Read more of what Rosen has to say on children and their sleep on his blog, Sleeping Angels.

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