(Agencies)
Updated: 2007-10-26 11:05

NEW YORK -- Children tend to vary widely in their sleep habits, with some being naturally "short sleepers" and others needing more time in bed, a study suggests.

Swiss researchers found that among 305 children they followed from ages 1 to 10, there was significant variability in how much sleep they typically got each night. However, most children -- 90 percent -- remained fairly steady in their sleep habits throughout childhood.

That is, children who were "short sleepers" or "long sleepers" as toddlers tended to be so later in childhood as well.

This suggests that biological makeup plays a large role in the amount of sleep any one child needs, the study authors report in the journal Pediatrics.

"We conclude from these findings that there is no optimal amount of sleep for the entire population of children," lead study author Dr. Oskar G. Jenni told Reuters Health.

Instead, "there is a wide range of 'normal' sleep duration among children," added Jenni, the director of the Child Development Center at University Children's Hospital Zurich.

Individual children in the study did show short-term fluctuations in the amount of the time they slept each night, according to parents' reports. And the average amount of sleep time naturally declined over the long term -- from more than 14 hours per day at age 1 to 10 hours at age 10.

However, over the 10 years, most children were stable in their sleep habits. Those who tended to sleep less than their peers in early childhood also did so at an older age, Jenni said; the same was true of long sleepers.

"We need to recognize that some children sleep less than others and vice versa," Jenni explained. Some parents, he noted, have a "set" bedtime for all of their children, but they should realize that each child may actually have different sleep needs.

Putting a naturally short sleeper to bed early in the evening could create sleep problems, including difficulty falling asleep and staying asleep all night, Jenni pointed out.

It's important to distinguish children who are naturally short sleepers from those who are getting too little sleep, according to the researchers. Children who wake up in the morning without difficulty and show no signs of daytime sleepiness are probably getting enough shut-eye.

On the other hand, children who are groggy during the day or have behavioral problems and trouble with schoolwork may be sleep-deprived.