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The Science of Sleep: How It Really Affects Kids

Image source: Thinkstock
Image source: Thinkstock


My son started first grade a few weeks ago, and life looks very differently now. In the summer, he’d spend plenty of mornings lounging in his PJs building Legos, eventually heading outside to play with a garden hose. Now, we never stop moving; mornings are a quick assembly line of clothes, breakfast, brushing teeth, sunblock, packing the backpack, and jumping in the car. After school, time moves just as quickly through playdates, activities, dinner and bedtime routines.

Like many parents, I wonder if my child is sleeping enough. The fact that sleep is squeezed by school is ironic, because sleep itself is one of the biggest contributors to our kids’ academic and social success. Children who sleep well are better able to think clearly and creatively, regulate their emotions, and perform better in school. For preschool and early-elementary-age kids, sleeping fewer than 10 hours per night has been linked to lower vocabulary and intellectual skills. In one well-known study, when researchers extended or restricted school age kids’ sleep by just 30 minutes, the difference in sleep made an impact equivalent to two years of academic level.

Why would a (seemingly) small amount of sleep — on the order of 30 to 60 minutes — make such a difference in how kids learn? There are many reasons for this. One is that sleep feeds our highest, most advanced brainpowers. Sophisticated thinking and complex emotional tasks — like making abstract connections to solve a math problem, or calming our emotions and communicating when a friend insults us at recess — require a set of brain skills called “executive function.” Executive function helps us organize ourselves into coherent, capable people; it’s frequently described as the “conductor of the orchestra,” or the “CEO of the brain.”

Unfortunately, executive function is very sensitive to sleep loss; it’s the first to go when children don’t sleep enough. Kids who miss 30 to 60 minutes of sleep might function just fine — eating, talking, playing — but their higher mental powers are affected: they lose their ability to focus and their creative edge falters, they don’t retain information as well, or they become emotionally fragile and quick to snap or melt down.

Toddlers need 12-14 hours of sleep, preschoolers 11-13, and school age children 10-11. But it can be hard to meet this need every night because of:

  • Irregular bedtimes and wake up times throughout the week, or between weekends and weekdays
  • A rushed or inconsistent bedtime routine
  • Less-than-optimal sleeping environments or sleep associations
  • Too many after-school activities (including homework), which leads to stress and not enough time to wind down

If you want the best sleep for your child, it’s important to think in terms of regularity and rhythms, rather than hoping they’ll catch up on the weekends. Changing sleep schedules is like giving your child a small case of jet lag. It confuses the body’s circadian system, which operates on regular 24-hour cycles. Irregular sleep schedules throw the body slightly out of whack and affect mood, behavior, and thinking. Moreover, when little ones go to bed at different times during the week (7:30 p.m. on weekdays but 9:00 p.m. on weekends), it leads to an accumulated “sleep debt,” because either they wake up at the same time on the weekend (they have powerful internal clocks), or they don’t sleep in quite enough to make up for the difference in bedtime — and 30 minutes here and there begins to add up.

In fact, studies have shown that a regular bedtime is as important as an early one. One recent study of 11,000 children, ages three to seven, showed that having a regular bedtime (independent of the actual time) was linked with better reading, math, and spatial abilities. Kids with irregular bedtimes also had more behavioral issues like moodiness and hyperactivity, and kids with late and irregular bedtimes were the hardest hit.

Sleep should be a priority around which we arrange life, rather than the other way around. Of course it doesn’t mean we can never be flexible, but staying up late should be the exception, with evenings arranged in a way that puts sleep first. Pick and choose activities to keep days balanced. After-school play dates and enrichment activities are fun, but too many mean that kids get home late and feel rushed. Your child’s brain takes cues from the environment, and it needs time to shift modes. Social activity, electronics, and light (both natural and artificial) tell the brain it’s time to stay awake. Softer light, calm voices, and consistent routines shift it to a relaxed state in which your child can welcome sleep. We can’t expect this to be like flipping a switch, either — it’s a gradual progression that starts roughly an hour before a child’s optimal bedtime. Just like most grown ups can’t come home from work and immediately hit the pillow (unless they’re really exhausted), our kids can’t be expected to hustle from homework or a friend’s house and into bed.

The more we respect this need and create the space for our kids’ good sleep at night, the better able they are to make the most out of their days.

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