Children who are poor sleepers more likely to be obese as adults

Nov 4 2008

According to new research regularly getting a good night's sleep as a child may help protect adults from becoming obese.

New Zealand researchers have found in a study which followed more than 1,000 children born in Dunedin between 1972 and 1973, that those who had too little sleep as children were more likely to become obese adults.

Dr. Robert John Hancox, the study's senior author, says even when a range of other factors such as childhood weight, TV habits, and adulthood exercise levels, were taken into account, a link remained between sleep deprivation during childhood and obesity later in life.

Dr. Hancox says although this cause-and-effect relationship cannot be proven, the study provides strong evidence to support the theory that early sleep habits have a direct effect on weight in the long term.

Dr. Hancox and his colleagues at the University of Otago in Dunedin, say a number of studies have found that sleep-deprived adults and children are at greater risk of being overweight but theirs is the first to confirm that short sleep during childhood could have long-term implications for adult obesity.

The study involved 1,037 men and women who had been followed since their birth up to the age of 32 - their parents reported on their usual bed time and wake-up time when the participants were 5, 7, 9 and 11 years old and the researchers say as childhood sleep time declined, adulthood body mass index, or BMI, climbed.

They found that adults who had been "short sleepers" as children - averaging fewer than 11 hours in bed each night - generally had a higher BMI than those who'd had more sleep as children.

Dr. Hancox says this is important because children who were short sleepers grew up to be short sleepers as adults and inadequate sleep in childhood appears to have long-lasting consequences.

According to the researchers, the results suggest that weight control may be another reason children need to get a good night's sleep.

Experts generally recommend that children between the ages of 5 and 12 sleep for about 11 hours each night, while teenagers should get 8.5 to 9.5 hours but there is a suspicion that today's children are getting less sleep than previous generations and Dr. Hancox believes this trend could be helping to fuel the rise in obesity.

Why a lack of sleep is linked to heavier weight is unclear but one theory is that sleep deprivation alters the normal balance of appetite-stimulating and appetite-suppressing hormones - also sleepy children may be too tired for physical activity during the day.

The research, published in the American journal Pediatrics, was funded by the Health Research Council.