Tots' Sleep Habits: Eye-Opening New Findings
But parents should still try to correct bad sleep habits, expert says
In general, such studies can help researchers sort out the influences of genes versus "shared environment," which could include anything from a mom's diet during pregnancy to family income.
When it came to hours slept at night, genes seemed to explain more than half of the variance among children at the ages of 30 months and 4 years. Genes were nearly as important at the age of 6 months.
The exception was the age of 18 months, when environment seemed to account for about half of the variance among the children.
As for napping, environment became a bigger influence as kids got older, explaining most of the differences in children's habits by age 4, Touchette said.
What can parents take away from all of this? "We've still got a lot to learn about children's sleep," Montgomery-Downs said.
For many parents, bedtime is anything but peaceful. Getting your child to settle down and fall asleep may be a battle, and then there are the questions: How much sleep is enough? Is your child waking up too often at night? Is he napping too much or too little?
There are no clear-cut answers, Montgomery-Downs said.
Experts have tried to come up with some general advice, based on what's typical for young children. According to the National Sleep Foundation, babies aged 3 months to 11 months sleep for an average of nine to 12 hours at night (total, not straight through), and take one to four naps during the day -- fewer as they approach 1 year. The average toddler gets about 12 to 14 hours of sleep over 24 hours, with most taking at least one daytime nap.
But that doesn't mean parents should worry if their child gets a little less sleep than that, or is stubborn about napping, Montgomery-Downs said. "Just because most kids average a certain amount of sleep doesn't mean that's the 'normal' amount," she said.
"We know that with adults, there's a lot of individual variation in how much sleep a person needs," Montgomery-Downs said. So children, too, may vary in how much sleep is enough, she said. But the research isn't there to know for sure.