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Growing consequences of not enough sleep

William Shakespeare must have known the value of a good night's sleep when he wrote that it "knits up the ravell'd sleeve of care" and was the "Chief nourisher in life's feast".

As a parent, you can no doubt write your own poem. An ode to "thine tired child's crabbiness and orneriness" perhaps. But the reasons for a good night's sleep go well beyond mood.

"If children are not sleeping well the consequences may be problems with behaviour, attention, learning, and memory," says Dr. Shelly Weiss, author of Better Sleep for Your Baby & Child: A Parent's Step-by-Step Guide to Healthy Sleep Habits and Pediatric Program Director at the Hospital for Sick Children in Toronto.

Less sleep, especially before the age of 41 months, has also recently been found to increase hyperactivity-impulsivity and to lower cognitive performance on neurodevelopmental tests.

Sleep may affect more than just your child's brain

Most research has concentrated on the cognitive or brain consequences of sleep loss, based on the belief that sleep is for the brain alone. However, there is growing evidence that short sleep duration results in metabolic changes that may contribute to the development of obesity, insulin resistance, diabetes, and cardiovascular disease.

According to a recent study from Johns Hopkins University, for each additional hour of sleep, the risk of a child becoming overweight or obese was lowered on average by 9%. The paper also showed that children who slept the least had a 92% higher risk of being overweight or obese compared to children with longer sleep duration.

"I probably will tell my children it's very important for them to have good sleep for their growth, health, and a [lack of sleep] may increase their risk of obesity too," says Dr Youfa Wang, co-author of the study and Associate Professor of International Health and Epidemiology at Johns Hopkins.

Which came first: the obesity or less sleep?

Although it is not clear how sleep affects children's weight, Dr Wang's research suggests children with short sleep have low caloric intake and expenditure. Sleep deprivation often leads to changes in the structure of sleep stage. As a result, children are tired, have somatic and cognitive problems, and in the end, do less because they are tired.

Sleep loss also leads to changes in several hormones including leptin, ghrelin, insulin, cortisol, and growth hormone. These hormonal changes may contribute to energy imbalance and lead to overweight or obesity.

So, how do I know if my child is getting enough sleep?

As the number of reasons and studies showing the value of enough sleep continue to grow and grow, how can you tell how much sleep your child should receive?

The quick answer: The amount of sleep a child needs depends on the child. Children of the same or similar ages need different amounts of sleep. A more helpful rule of thumb is: if your child wakes up groggy or is sleepy during the day, he's not getting enough sleep. In these instances, you should consider making his bedtime earlier.

As children get older, they need less sleep. Although there is no magic number for how much sleep your child needs, knowing how much sleep most children your child's age get, can help you gauge your child's sleep requirements.

Average sleep amounts by age

  • 0 to 2 months: 16 to 18 hours per day. But newborns rarely sleep for more than 5 hours at a time. Newborn babies wake up when they are hungry and sleep when they are full or tired. Until the age of 6 months, the part of a baby's brain that controls when he goes to sleep and wakes up is not developed yet.
  • 2 months to 6 months old: 14 to 16 hours. This time may include naps.
  • 6 to 12 months: 13 to 15 hours. By about 6 to 8 months, the baby will start to sleep closer to the times that the rest of your family sleeps. Then by about 9 months, about 7 out of 10 babies will sleep through the night. He will usually wake about 6 hours after he falls asleep, then eat. After eating, he will fall asleep again.
  • 1 to 3 years: 12 to 14 hours
  • 3 to 5 years: 11 to 13 hours
  • 5 to 12 years: 10 to 11 hours
  • 12 to 18 years: 8.5 to 9.5 hours

Figure out what time most kids your child's age go to bed

Use this clock to figure out what time most kids your child's age go to bed, based on when they wake up.

  1. Sleeptime Calculator
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    Write down how many hours of sleep most kids your child's age get each night: _________________
  2. Next, mark on the clock what time your child wakes up each morning.
  3. Now, using the clock, count back according to the number of hours of sleep most kids his age get each night. Where you stop is when most kids his age go to bed, based on when he wakes up.

Usual bedtime for children my child's age: _______________________

For example, Cassandra is 9 years old. So we know that most kids her age get at least 10 to 11 hours of sleep each night. She wakes up at 7:00 each morning. Counting backwards from 7:00 am, we can figure out that most kids her age go to bed no later than 9:00 pm each night.

Oliver is 4 years old. So we know that most kids his age get 11 to 13 hours of sleep. Oliver wakes up the same time as Cassandra in the morning. But, because he is younger, we know that most boys his age go to bed no later than 8:00 each night.

Is your child getting enough sleep? Take the test

If you can answer yes to all of these questions, your child is getting enough sleep:

  • My child falls asleep in less than 20 to 30 minutes of bedtime.
  • My child wakes up easily in the morning, at the expected time.
  • My child appears well rested during the day.
  • My child stays awake without taking a nap during the day. (This question only applies to children that have outgrown their daytime nap.)
  • My child stays awake during quiet activities, such as driving in the car or watching television.

Symptoms of not enough sleep

If you or his teacher can answer yes to any of these questions, your child is not getting enough sleep.

  • My child has a hard time waking up in the morning.
  • My child falls asleep after being woken up and needs parents to wake again or repeatedly.
  • My child yawns frequently during the day.
  • My child complains of feeling tired.
  • My child prefers to lie down during the day, even if it means she'll miss activities with friends and families.
  • My child wants to nap during the day.
  • My child lacks interest, motivation, and attention.
  • My child falls asleep or seems drowsy at school or at home during homework.

When should I take my child to the doctor for a sleep problem?


Take your toddler or preschooler to the doctor if he has any of the following:

  • medical problems or pain that is affecting his sleep
  • persistent and loud snoring or pauses or problems breathing while sleeping
  • he seems irritable, hyperactive, inattentive or sleepy during the day
  • excessive anxiety about being separated from you during the day and night
  • problems with sleep that just developed
  • problems changing from two naps to one nap a day
  • night terrors, sleepwalking, or nightmares that happen often

School-aged child

Take your child to the doctor if he has any of the following:

  • your child's teacher tells you he seems tired even though you think he gets enough sleep
  • new night terrors or sleepwalking that he didn't have before the age of 6 to 7 years
  • a need for regular naps
  • loud snoring, breaks in his breathing, or extreme restlessness at night


Take your teenager to a doctor if he has any of the following:

  • excessive sleepiness during the day
  • lower grades in school
  • you suspect a mood disturbance
  • concerns about sleep or daytime performance

Consistency is key to catching more Zs

"With regards to sleep habits, children will respond best if parents are consistent, and they know what is expected of them. Sleep habits which should be consistent include bedtime routines, bedtime, and wake times," says Dr. Weiss.

If your child does not get enough sleep one night, just figure out the number of hours he missed and slowly add a few hours each night after to make up for the lost time. This may mean having him going to bed earlier or sleeping in more, when possible, the next morning.

To encourage good sleep habits, remove the TV, computer, and video games from your child's bedroom. Allow your child to sleep in, but no more than 2 to 3 hour beyond his usual wake time. He can do his part too by doing the following:

  • avoiding nicotine, alcohol and drugs, and caffeinated drinks after lunchtime
  • avoiding activities that may be arousing around bedtime, such as heavy studying, computer games, and text messaging on cell phone
  • avoiding bright light in the evening and when waking up in the morning
  • avoiding staying up all night

Be the sleep model for your child

Setting earlier bedtimes and getting ready for the next day the night before helps everyone sleep better. If you model good sleep habits, your child will also learn them, points out Dr. Wang. "Prepare those items regarding their own work and their children's school at night time to teach your child good sleep habits."

It may also be a good idea to explain that "growth hormone is secreted mainly during sleep," says Dr Wang.

Regardless of the amount of sleep your child needs, "The more consistent parents can be with regards to regular sleep habits, the more likely the child will have better sleep," says Dr Weiss.

And who knows? When we wake up tomorrow, research may have found even more reasons for you to tell your child to "go back to sleep."

More information on sleep


Better Sleep For Your Baby And Child, by Dr. Shelley Weiss

Web sites: pages about sleep

Canadian Sleep Society

National Sleep Foundation

Kimberly Humphreys
Medical Writer/Editor, AboutKidsHealth


Chen X, Beydoun MA, Wang Y. Is sleep duration associated with childhood obesity? A systematic review and meta-analysis. Obesity. 2008;16(2):265-274.  

Gibson ES, et Obesity. 2008;16(2):265-274al. Sleepiness is serious in adolescence: Two surveys of 3235 Canadian students. BMC Public Health. 2006; 6: 116.

Hitti M. More sleep, less childhood obesity.

Taheri S. The link between short sleep duration and obesity: we should recommend more sleep to prevent obesity. Archives of Disease in Childhood. 2006 Nov;91(11):881-4.>

Touchette E, et al. Associations between sleep duration patterns and behavioral/cognitive functioning at school entry. Sleep.2007 Sep 1;30(9):1213-9.

University of Michigan Health Systems. What's there to know about sleeping?

Wang Y, et al. Obesity Prevention among Low-Socioeconomic Status African American Adolescents: The HEALTH-KIDS Study. European Journal of Clinical Nutrition. 2006;60:92-103.

Weiss SK. Better Sleep for Your Baby and Child. A Parent's Step-by-Step Guide to Healthy Sleep Habits. Toronto: The Hospital for Sick Children. Robert Rose, Inc.; 2006.