Several years ago, University of Michigan researchers published some of the strongest evidence yet that children who snore when they sleep are far more likely to have attention and hyperactivity problems than their non-snoring peers.
Today, that link takes on a new long-term dimension with the publication in the journal Sleep of follow-up data from some of the same children who took part in the earlier study.
Indeed, children in the original study who snored regularly, in comparison to those who did not, were about four times more likely to have developed new hyperactivity by the time the U-M team contacted their families four years later. In other words, snoring early in life predicted new or worsened behavior problems four years later.
Similar behavior was seen among children who had had other symptoms of obstructive sleep apnea, in which repeated pauses in breathing disrupt sleep and can reduce blood oxygen levels. For example, children with daytime sleepiness in the original study were also more likely to have developed hyperactivity four years later.
The findings held true even after the researchers took into account which children already had been identified as hyperactive during the first study, and which ones were taking prescription behavior medicines during the follow-up survey. In fact says lead author and U-M sleep researcher Ronald D. Chervin, M.D., M.S., inattention and hyperactivity at follow-up were usually predicted better by snoring and other sleep apnea symptoms four years earlier than by those same symptoms at follow-up.
One group, the boys who were under the age of 8 and had the worst sleep-breathing problems during the first study, were approximately nine times more likely to have developed new hyperactivity four years later than boys of the same age who hadn’t had such sleep problems.
The results are from a prospective study of 229 children who are now between the ages of 6 and 17. The children were drawn from the group of 866 2- to 13-year-olds whose parents were originally surveyed in the late 1990s, in the waiting rooms of several community-based pediatrics clinics. The parents agreed to allow the researchers to mail them a follow-up survey four years later; 229 returned it. The follow-up group was statistically comparable to the initial group.
Both at the baseline and at follow-up, the parents completed standardized questionnaires that measure a child’s behavior and sleep characteristics. Children were encouraged to help their parents complete the questionnaires.
The initial study, published in March 2002 in the journal Pediatrics, found that kids who snored regularly were twice as likely as non-snorers to have hyperactivity or attention issues at the same time. Among boys under the age of 8, the rate was four times.
“To our knowledge, this new study is the first long-term, prospective research to show that regular snoring and other clues to the possible presence of sleep apnea predict future development of inattention and hyperactivity,” says Chervin, M.D., M.S., the director of the U-M Health System’s Michael S. Aldrich Sleep Disorders Laboratory and associate professor of neurology at the U-M Medical School. “These findings strengthen the hypothesis that untreated sleep-breathing problems in childhood can contribute to the development of hyperactivity.”
Chervin and other sleep and breathing researchers have built up a large body of evidence on this issue in recent years. The sleep-behavior link rests on the concept that snoring, sleep apnea and other breathing problems during sleep diminish the quality of sleep, repeatedly reduce oxygen levels, and affect daytime behavior.
Data from small groups of children who received treatment for their sleep-breathing problems - usually by removal of the tonsils and adenoids — have indicated that behavior may improve as sleep improves. Larger studies of pre- and post-treatment sleep and behavior patterns are now underway; Chervin and his colleagues are currently analyzing data from one performed at U-M.
But definitive proof that breathing problems during sleep affect daytime behavior is still elusive, the U-M authors write. And a long-term randomized controlled trial, the gold standard of medical research, might never be done because it would require researchers to withhold treatment that has become an accepted standard of care.