We’d all like to sleep like babies. But not all babies sleep the same amount, say researchers at Laval University in Quebec, whose study of nearly 500 pairs of Canadian twins published online yesterday in the journal Pediatrics found that genes are a stronger determinant than the environment of how long babies and toddlers sleep at night.


In this study, mothers reported on their children’s day- and nighttime sleep patterns at 6, 18, 30, and 48 months. A majority of the children slept 10 to 11 hours a night, but the outliers did not. Except in twins of 18 months, when environmental factors were found to play a stronger role in determining sleep length at night, genetic factors accounted for up to 58 percent of the variation in nighttime sleep duration. Environmental factors had a more important effect on the length of daytime naps.

This study adds to a growing body of literature suggesting that aspects of sleep such as sleep length and sleep quality are part of a genetic blueprint inherited at birth. As such, while they can be altered by changes in habit and environment, there are limits on the modifications we can achieve.

Taking Control of Sleep

In my book I argue that there’s a lot people can do to improve their sleep by changing their environment, habits, and thoughts. And the researchers who conducted this study maintain that parents can be proactive in shaping an environment conducive to children’s sleep.

“[Parents] should not give up on trying to correct inadequate sleep duration or bad sleep habits early in childhood,” lead researcher Evelyne Touchette said in an article in usnews.com.* Setting consistent bed- and naptimes and doing a quiet activity such as reading a story are two things parents can do to establish optimum conditions for children to sleep.

Giving Nature Its Due

But to discount the constitutional factors that affect sleep ability seems foolish in light of emerging genetic research. In 2009, for example, investigators found a genetic mutation in a mother and daughter who normally wake up feeling fine after sleeping an average of six and a quarter hours. Other members of the same family, who average eight hours’ sleep, do not have this rare mutation.**

A more common genetic factor affecting sleep length came to light in 2011. Scientists studying a large pool of Europeans identified a genetic variant which they claim accounts for about 5 percent of the variation in sleep duration. Their data show that people who possessed two copies of a common variant of a gene slept significantly less than people with two copies of another version.***

If you or your child isn’t getting enough sleep, do all you can to set up ideal conditions for slumber at night. Yet past a certain point, some things may be beyond our control, and how long we sleep is one.

How much sleep do you get at night? Has this changed over time?

*    Tots’ Sleep Differences Due to Genes

**   Sleep Length in Mammals

*** Gene Effect on Sleep Duration

Posted by Lois Maharg, The Savvy Insomniac

Lois Maharg has worked with language for many years. She taught ESL, coauthored two textbooks, and then became a reporter, writing about health, education, government, Latino affairs, and food. Her lifelong struggle with insomnia and interest in investigative reporting motivated her to write a book, The Savvy Insomniac: A Personal Journey through Science to Better Sleep. She now freelances as an editor and copy writer at On the Mark Editing.


  1. Two of our grandchildren were helped to sleep w/ “white noise sounds”, little whirring boxes of sound set in place by parents to buffer all other sounds in the environment (especially that of siblings, telephones, home sounds in general).



  2. Great idea. Quite a few adults I interviewed for my book also used white noise machines. Anything that’s soft and monotonous. Marty Stauffer’s voice, on Wild America, worked for me!



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