Wednesday, October 10, 2007

Naps and Other Make-up Sleep

From Ash & Po:

A couple people have asked us about naps (for school-aged and older kids) and sleeping in – great questions we'd wondered, too.

If your kid is tired, then, by all means, let the kid sleep in or take a nap.

Let's kill the myth that sleeping in or napping is part of "lazy afternoon." Physiologically, you can't sleep unless you actually need to sleep. That's the homeostatic pressure part of sleep at work. So there's nothing lazy about getting needed sleep. (Conversely, being awake and sleep-deprived will probably lead to more lethargy than if he'd actually just slept more.)

Moreover, sleep loss is cumulative, so the only way to make up for it is to get more sleep on another night or during a nap.

But – and this is the big caveat – don't treat sleeping in or naps as a cure-all. Instead, they are the sleep-equivalent of band-aids. They shouldn't be something that you rely on, instead of having a kid get a regular nightly sleep schedule.

Here's why.

Sleeping in and naps do help resolve the sleep debt, but they probably won't resolve the debt entirely. As an example, let's say that a particular teen does need the 9.25 hours a night recommended by many sleep experts. But he only gets seven hours on school nights. On Monday, he's down 2.25 hours. That's not great, but we've all been there, right? By the end of the week, he's short 11.25 hours of sleep – he's missed more than an entire night's worth of slumber. Even sleeping in until noon on Saturday will probably only have helped erase two or three of those lost hours.

Much more daytime sleep than that, however, will likely throw off a kid's circadian rhythm and homeostatic pressure – so he'll may have more trouble going to sleep in the evenings, and wake up already sleep-deprived the next Monday morning. (That's even more of a concern for a teen, whose circadian system already has a preference for nighttime wakefulness.)

The amount and quality of sleep a person needs in a given night is directly related to the mental and physical activity that a person did during that very day. To the point that if you learn more vocabulary, you likely will spend more time in REM stage sleep. Make-up sleep can't handle those sleep stage adjustments as well.

Naps also bring unique problems of their own. That horrible groggy feeling after some naps is called "sleep inertia" – the body can't wake up fully. That's a real issue, but scientists don't know why it occurs or what it means.

What they do know is that the brain can't do the same sort of work during a nap that it does during nightly sleep. Consider that a nice nap is about 25 to 45 minutes. That's only 1/4 to 1/2 as long as it takes to cycle through all of sleep-stages of non-REM and REM sleep, and the brain needs to process information throughout all the stages of sleep.

Interestingly, a nap works best if it's prophylactic: if you know the kid's going to have a late night, then an afternoon nap can help him stay alert later in the evening. But even that is of limited use: he'll be just as tired the following day as if he hadn't had the nap.

Ultimately, let them get that make-up sleep.

But the more make-up sleep they need, the more you should think about changing their overall sleep schedule.



Anonymous Anonymous said...

Hi Ashley:

I always enjoy your articles so much and those of Po. All the best to you both!

Keep up the great work and writing! Thanks for keeping us informed.

9:24 AM  

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