Toronto, Nov 19 (IANS) More than a quarter of children who don’t get adequate sleep become either overweight or hyperactive, says a Canadian study.This pattern may continue into their adult life, the study’s authors warn.

Carried out by Montreal University researchers, the study also says that nearly 90 percent of children between ages of six months and six years suffer from at least one sleep-related problem - nightmares, teeth grinding or bed-wetting.

About 30 percent children in this age group also have difficulties in getting continuous sleep for six hours, the study points out.

The researchers analysed data on the sleeping pattern of 1,138 children as part of their study.

They found that that 26 percent of those who didn’t sleep enough were overweight, 18.5 percent had extra weight, and 7.4 percent were obese.

According to Jacques Montplaisir, study leader and university psychiatry professor, the overweight 26 percent children slept fewer than 10 hours a night between two and a half years and six years. About 15 percent of them slept 10 hours and 10 percent slept 11 hours.

Explaining the link between sleep and excess weight, he said lack of sleep changes the secretion of hormones that increase appetite for food.

“When we sleep less, our stomach secretes more of the hormone that stimulates appetite. And we also produce less of the hormone whose function is to reduce the intake of food,” said Montplaisir.

The study also found that 22 percent of children who slept less than 10 hours started showing hyperactivity by the age of six.

This is twice the rate seen among those who slept 10 to 11 hours.

Montplaisir said it was lack of sleep which leads to hyperactivity, not the other way about. “In adults, inadequate sleep translates into sleepiness, but in children it creates excitement,” he explained.

To know how lack of sleep affected their learning, the researchers asked the children to copy a picture using blocks of two colours.

They found that 41 percent of children who lacked sleep performed poorly. But only 17 to 21 percent of those with 10 or 11 hours of sleep performed badly.