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Nurture Shock: Chapter 2 – The Lost Hour

Po Bronson wrote the article “Snooze or Lose” which questions whether a lack of sleep can set back your child’s cognitive abilities?  This is essentially chapter 2 from the book Nurture Shock.

If you want to skip reading the book, then here’s the answer:

Yes it can.  I referred to this article briefly in a blog post written about a year ago, but here are the real implications of losing as little as one hour of sleep a night – if you’re a child under the age of 21, that is.

The Problem

Children today are averaging an hour less sleep a night than children 30 years ago.

The Effect

Sleep studies performed on children are revealing that a single lost hour of sleep a night can:

  • reduce academic performance
  • affect emotional stability
  • increase the incidence of medical conditions such as obesity and Attention Deficit Hyperactivity Disorder (ADHD)

Sleep deprivation during the formative years of a child’s brain could lead to permanent changes in brain structure that cannot be reversed even with “catch-up” sleep.

1. The Effect of Sleep Deprivation on Academic Performance

A sleep deprivation study on a group of elementary students revealed that sixth graders, missing one hour of sleep a night, performed in class at the level of a fourth grader.  Effectively, losing one hour of sleep a night can reduce a child’s cognitive maturation and development by as much as two years.  Additionally, delaying a child’s bedtime by one hour over the weekend can lead to a seven point reduction in IQ scores.  Even 15 minutes of sleep can mean the difference between an average grade A student and an average grade B student.

Sleep deprivation impairs a child’s brain by reducing the plasticity of that child’s brain cells. The brain cells are then unable to form the connections required to record memory.  Therefore, children suffering from sleep deprivation are not able to retain information learned in class.  Sleep is vital for the synthesis and storage of memories.  During sleep, the brain moves information learned during the day into more efficient storage areas within the brain.  The more a child learns during the day, the more sleep is required to consolidate the memories associated with the information learned.

Sleep deprivation also affects the body’s ability to draw glucose from the bloodstream.  This inability to access basic energy reserves from the body affects the prefrontal cortex of the brain.  The prefrontal cortex is responsible for executive functions such as fulfilling goals, predicting outcomes, and perceiving the consequences of actions.  When the brain is tired, it is unable to look beyond a wrong answer and come up with alternative solutions.  It is also unable to control impulses such as postponing entertaining diversions in order to complete study goals.

2. The Effect of Sleep Deprivation on Emotional Stability

Studies have also shown an interesting effect of sleep on different parts of the brain.  For instance, sleep deprivation impacts the hippocampus more so than the amygdala.  The hypocampus is responsible for processing positive memories, while the amygdala processes negative stimuli.  As a result, children who are sleep deprived are less able to recall pleasant memories compared to melancholic ones.

3. The Effect of Sleep Deprivation on Weight

Sleep studies have revealed that children who sleep less are, on average, fatter than children who receive adequate sleep.  Children who received “less than eight hours of sleep have about a 300 percent higher rate of obesity than those who get a full ten hours of sleep.”  The two-hour window revealed a “dose-response” relationship between sleep and obesity.

How does sleep deprivation affect weight gain?

  • Lack of sleep has been shown to increase the hormone that signals hunger and reduce the hormone that suppresses appetite.
  • Lack of sleep increases the levels of the stress hormone cortisol which stimulates the body to make fat.
  • Sleep deprivation disrupts the normal release of human growth hormone which is essential for breaking down fat.

So there you have it – even losing as little as an hour of sleep a night has an enormous impact on anyone under the age of 21.

While we’re on the topic of sleep, it should also be noted that studies performed on adults who were averaging about 6 hours of sleep a night functioned similarly to individuals who had not slept in 24 hours.  It’s not just the children that suffer from a lack of sleep, however, it is the children that have the most to lose from that missing hour.

Teenagers and Sleep

Although I don’t really have a teenager to worry about right now, I figured it was worth remembering this point when Gavin and Gareth become teenagers.  This wasn’t mentioned in the New York Magazine but it was written in the book Nurture Shock.  Apparently, the problem with teenagers and sleep is that during puberty, teenagers go through “phase shift” in their circadian rhythms which keeps them up later – about 90 minutes later.

In adults and prepubescent children, the brain begins to produce melatonin when it gets dark outside.  Melatonin is responsible for making us feel sleepy.  Unfortunately, in teenagers, the release of melatonin does not occur for another 90 minutes.  This alone is not particularly significant until you combine it with an early start the following morning.  When the alarm rings in the morning, teenagers are still producing melatonin and are prone to falling back to sleep – usually in the first two periods of school.

Since teenagers are also affected by sleep deprivation in the same way, this inadvertent reduction in sleep has a significant impact.  In fact, it is believed that the lack of sleep that teenagers suffer is also related to the common “moodiness” observed in teenagers.  Even those that do not suffer from clinical depression are likely to be affected by some level of melancholy.

Unfortunately, the answers to this are not simple – unless you can find a school with a later start to send your teenager to.


Published by Shen-Li

SHEN-LI LEE is the author of “Brainchild: Secrets to Unlocking Your Child’s Potential”. She is also the founder of (a website on parenting, education, child development) and (a website on Right Brain Education, cognitive development, and maximising potentials). In her spare time, she blogs on Forty, Fit & Fed, and Back to Basics.

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