One-fourth of overweight children may have sleep problems that regular physical activity can largely resolve, researchers say.

Research published in the November issue of Obesity shows a surprising 25 out of 100 overweight, inactive children tested positive for sleep-disordered breathing, including telltale snoring.

After about three months of vigorous after-school physical activity such as jumping rope, basketball and tag games, the number of children who tested positive for a sleep disorder was cut in half, according to lead researcher, Dr. Catherine L. Davis. In children who exercised the longest, the number was reduced by 80 percent.

The children were among 100 black and white boys and girls ages 7 to 11 enrolled in a study looking at the effect of exercise on metabolism. For the purposes of that study, the children were divided into three groups: a control group as well as those who exercised 20 or 40 minutes daily.

In fact researchers found the average score for all children who exercised – even those who did not test positive for sleep disorders – improved on the Pediatric Sleep Questionnaire.

“Existing data suggests about two percent of children have sleep problems but with 37 percent of children now considered overweight, the percentage may be much higher,” says Dr. Davis, clinical health psychologist at the Medical College of Georgia and the study’s first author.

“We believe this study is a red flag to pediatricians to ask parents about their children’s snoring,” she says. “Snoring does not appear to be benign in children. Not sleeping well can affect children’s behavior, their ability to function in school. We don’t know yet if it affects their development.”

“The long-term consequences of sleep-disordered breathing on children are unknown,”’ study authors write. “There may be lasting benefits of prevention or amelioration of sleep-disordered breathing as a result of protection from neural insult during childhood.”

Dr. Davis likens the possible increase in sleep-disordered breathing in children, which includes sleep apnea and less severe problems, to the increasing incidence of lifestyle-related type 2 diabetes. “Nobody used to think type 2 diabetes happened in kids either,” says Dr. Davis who studies the impact of exercise on the risk of the disease in children. “We thought type 2 diabetes was something you got at maybe 50, not 15. It has become a major media sensation because it is so shocking.”

When Georgia researchers first gave the Pediatric Sleep Questionnaire, which looks at symptoms of sleep disordered breathing – such as snoring, loud breathing and daytime inattentiveness – they were surprised as well by how many children tested positive.

The questionnaire, given to parents, has been shown to provide results similar to those of polysomnography, a monitoring of physiological activities such as breathing during sleep. “We asked parents about caffeine intake, medications, usual bed and wake times to see if the children are chronically sleep-deprived, asked if they had a tonsillectomy because that usually fixes sleep apnea in children,” Dr. Davis says.

Interestingly sleepiness was not an issue because children instead tend to display attention deficit/hyperactivity disorder-type behavior when they don’t get enough sleep, she says. Caffeine intake also may have played a role in subverting sleepiness, the researchers say.

Also, the body mass index, based on height, weight, age and sex, did not improve as children exercised and became asymptomatic. However the growing children got fitter, built muscle and lost fat, Dr. Davis says. “It affects their fatness, their fitness, their cardiovascular risk factors, it’s just their weight doesn’t go down without a change in diet, just like adults,” she says. Adult studies have shown a similar relationship between obesity and sleep apnea and how exercise can ameliorate sleep apnea.

To learn more about sleep patterns in overweight children, Dr. Davis has started a similar study using wristbands to record movement during sleep and fingertip pulse oximeters to measure oxygen levels.

Dr. Amy R. Blanchard, pulmonologist and director of the MCG Georgia Sleep Center, is working with Dr. Davis on the new study and hopes their monitoring approach will prove an effective, inexpensive and unobtrusive way to identify early problems.

“It may give us an early diagnosis of something that could potentially affect their outcome in many ways,” says Dr. Blanchard who has been surprised by the amount of sleep disruption they’ve already seen in the children, some of whom are only slightly overweight. She notes that some may even be playing video games or watching television when they are supposed to be sleeping, further detracting from a good night’s rest.

“Kids can have sleep apnea for a couple of reasons,” she says. “A normal-weight child can have sleep apnea because they have big tonsils and adenoids and many times their problems can be cured with surgery.”

Gaining weight can exacerbate sleep problems or even cause them by contributing to a narrowed airway, she says. The child lies down, throat muscles relax, the tongue falls back, the airway gets obstructed, oxygen levels may drop, the child is aroused and the cycle begins again. Snoring, present in essentially everyone with sleep apnea, results from the vibration of excess tissue – whether it’s fat, large natural anatomy or both – as the child breathes in.

“The published study suggests we need to be looking more diligently at kids, not necessarily just kids with big tonsils who snore, but any child that is snoring or heavy,” Dr. Blanchard says. “It’s just like in adults, when doctors start asking their patients, they find a lot of people snore.”

The published research was funded by the National Institute of Diabetes & Digestive & Kidney Diseases.