MONDAY, March 5 (HealthDay News) -- Infants and toddlers who snore or have other breathing issues while sleeping are more likely to develop behavioral problems by the age of 7, new research suggests.

Those issues can include hyperactivity and inattention, emotional problems such as anxiety and depression, conduct problems such as rule-breaking and aggressiveness and problems with peer relationships, researchers said.

The study is published online March 5 and in the April print issue of Pediatrics.

The researchers assessed more than 11,000 children in England, who were followed for six years, beginning when the kids were 6 months old.

Parents were asked about snoring, mouth breathing and witnessed apnea -- when a child takes abnormally long pauses in breathing during sleep -- at various points throughout infancy and childhood. Taken together, those symptoms are called sleep-disordered breathing.

Parents also filled out questionnaires about their child's behavior at the ages of 4 and 7.

Those who had the worst sleep-disordered breathing were almost twice as likely to have behavioral issues at age 7 as kids whose breathing was normal. Kids were considered to have behavioral issues if their parent's ratings were in the top 10 percent, relative to kids their age, for problem behaviors.

"Parents should pay close attention to their child's sleep, and if you think something is going on you should consult a pediatrician or a sleep specialist," said study author Karen Bonuck, a professor of family and social medicine at Albert Einstein College of Medicine of Yeshiva University in New York City.

The research showed only an association between sleep-disordered breathing and behavioral problems, not causality. However, there could be several reasons for the connection, Bonuck said.

By interfering with the quality of rest, sleep-disordered breathing leaves kids overtired. That may contribute to behavioral issues, such as being easily distracted, hyperactivity and irritability.

Previous research has also suggested that sleep-disordered breathing affects brain physiology via a lack of oxygen to the brain, carbon dioxide buildup and abnormal gas exchanges, Bonuck explained. For children, that may have a long-lasting impact.

"We are sleeping to restore our brains, and sleep-disordered breathing interferes with that process," Bonuck explained. "For kids, these are critical periods in brain development."

Heidi Connolly, division chief for pediatric sleep medicine at University of Rochester Medical Center in New York, said the study adds to a growing body of research showing that snoring, mouth breathing and sleep apnea in children should be taken seriously.

"These findings echo many of the other studies that show having sleep apnea and symptoms of snoring are bad for neurodevelopmental outcomes in children," Connolly said.

While snoring is a symptom of sleep apnea, it can have other causes, such as nasal allergies. Other studies suggest that even snoring alone, without apnea, can cause kids to do worse developmentally, she added.

"We need to think of that in primary care settings, and screen children for snoring," she said. "Kids who snore need to be evaluated and treated promptly, as you would any other medical condition."

Snoring occurs when the palate and the base of the tongue vibrate against each other. In sleep apnea, the airway is blocked. When kids try to breathe, negative pressure squeezes the airway shut, Connolly explained. That causes kids to wake up partially to take a breath.

Obesity is a major risk factor for sleep apnea in children, but normal-weight kids can get it, too.

"If your child is snoring on a nightly basis, not just when they are exposed to tobacco smoke or they have a cold or they just hung out with the neighbors' cat that they're allergic to, those children need to be evaluated for sleep apnea," Connolly said.

Treatments can include removing the tonsils and adenoids; topical nasal steroids or other anti-inflammatory medications; weight loss; and continuous positive airway pressure (CPAP) devices.

The researchers broke down kids with sleep-disordered symptoms into four groups: those whose symptoms were the worst at 6 months of age and then abated; 18 months and then abated; those whose symptoms didn't start until they were about 3.5 years old and then persisted; and those whose symptoms peaked at 2.5 years of age and persisted.

Nearly all four groups had an increased risk of various problems, including emotional, conduct and peer issues.

For example, at age 7, kids with "worst" sleep-breathing problems were 85 percent more likely to hyperactive, about 60 percent more likely to have emotional or conduct problems and nearly 40 percent more likely to have peer difficulties.

Children whose symptoms peaked early -- at 6 months or 18 months -- were 40 percent to 50 percent more likely to have behavioral problems at age 7, compared with normally breathing children.

More information

The American Sleep Apnea Association has more on sleep apnea in children.