How much sleep do kids need?

Silvia Araya,* mom to Adrian, 9, and Christina, 13, fondly remembers the slumber-filled days of her children’s early years. “When my kids were babies, they took a lot of naps and slept for long hours. But now, with school and busy schedules, they’re sleeping much less,” she says. Adrian’s bedtime is 8 p.m. and he gets about 11 hours of sleep; Christina goes to bed at 9 or 10 p.m. and gets eight to nine hours.

Like many parents, Araya relies on signs from her kids — drowsiness, irritability, difficulty concentrating—to determine how much sleep they need, more than calculating exact amounts. Both Adrian and Christina happen to fall within the latest guidelines.

How much sleep do kids need?

For about a decade, the paediatric sleep community has recommended that children three to five years old need 11 to 13 hours, children five to 10 years old need 10 to 11 hours, and adolescents 10 to 17 years need eight-and-a-half to nine-and-a-half hours of sleep each night.

But three studies published over the last year have brought forward new, and at times contradictory, information. The first, conducted at Brigham Young University in Utah, claims that less is actually more when it comes to neonate and teen sleep totals. The BYU scientists analyzed nearly 2,000 school children, and found that the kids who performed best academically were sleeping less as they got older. For 10-year-olds, the optimal snooze time was nine to nine-and-a-half hours; for 12-year-olds, it was eight to eight-and-a-half hours; and for 16-year-olds, it was only seven hours.

Study co-author Mark Showalter speculates that those extra hours of waking time are spent studying instead of sleeping, thus improving grades. “Most of our students at BYU realize that nine hours of sleep a night isn’t what the top students [get],” he observes.

A subsequent study in the journal Pediatrics called into question the validity of sleep guidelines in general. The paper (“Never Enough Sleep: A Brief History of Sleep Recommendations for Children”) surveyed sleep literature from the 19th century to 2009. It found that children’s sleep duration has declined steadily by 0.73 minutes a year — modern-day kids sleep less than our ancestors did—and that the recommended amount of shut-eye was always about 37 minutes more than what children were actually getting, whether the year was 1897 or 1997. It also found that most sleep recommendations were based on subpar experimentation, and that “there is almost no empirical evidence for the optimal sleep duration for children.”

Does losing one hour of sleep making a difference?

Add to the stack a recent study from McGill University in Montreal that confirms something most parents already know: When children ages seven to 11 sleep a single hour less than usual, they exhibit increased behavioural problems, including irritability, frustration and difficulty paying attention. Those who slept an hour extra were better behaved.

Penny Corkum, a paediatric sleep researcher in Halifax, agrees that taking away even an hour of sleep from a healthy child will cause near instant changes in mood, attention and functioning. She says that 10 hours in dreamland is optimal, but some kids may need even more. “It’s important to remember that these are just guidelines. They’re not definitive and need to be interpreted individually.”

Corkum is most intrigued by the historical study that found sleep has declined precipitously over the past 100 years. “Biology doesn’t allow for that kind of adaptation.” Children are losing sleep faster than their bodies can possibly evolve to perform well on less sleep, she says.

So while there is evidence that older kids who sleep a little less may get better grades, it seems reducing sleep time in order to improve your child’s marks makes little sense.

*Names have been changed.

A version of this article appeared in our February 2013 issue with the headline "Sleep on it," p. 50.

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