MONDAY, May 5 (HealthDay News) -- Children who wet their beds frequently have elevated levels of a heart hormone that helps regulate levels of fluid around the heart, a new study finds.

Additionally, children who habitually snore are about three times as likely to wet the bed as children who don't snore, but the severity of snoring appears to have little effect on the risk of bed-wetting, according to the research, which is published in the May issue of Pediatrics.

"Our findings were really an eye-opener," said study co-author Dr. David Gozal, director of the division of pediatric sleep medicine at the University of Louisville, in Kentucky. "Why children with bed-wetting have high levels of this hormone; that will require a bit more research."

About 9 percent of boys and 6 percent of girls at age 7 have trouble sleeping through the night without wetting the bed, according to the U.S. National Institutes of Health. The problem -- which affects about 5 million American children -- runs strongly in families. Nighttime bed-wetting, which is also called enuresis, is not the fault of the child or parent. For some reason, the child's brain isn't responding to normal cues to wake up and empty the bladder.

Because so many children who snore seem to also wet the bed, Gozal and his colleagues wanted to investigate the connection between the two problems.

The researchers reviewed almost 18,000 surveys completed by parents of 5- to 7-year-old children to see how many were habitual snorers or had problems with enuresis. From that group, they found that 1,976 children -- about 11 percent -- were habitual snorers. Fifty-three percent of those with habitual snoring were boys. About 27 percent of that group also wet the bed. Nearly 90 percent of those who wet the bed were boys. Among non-snoring children, just 11.6 percent wet the bed. As with the snoring group, almost 90 percent of those with enuresis were boys.

"The risk of bed-wetting for children who snore was about threefold," said Gozal.

But, the researchers also found that the severity of snoring didn't appear to change the risk of bed-wetting when they examined a smaller group of 60 children who wet the bed during sleep lab studies. Twenty of the children had obstructive sleep apnea; 20 had habitual snoring but no sleep apnea, and 20 didn't snore at all.

The researchers did find that levels of a heart hormone, brain natriuretic peptide (BNP), were raised in children who wet the bed. That finding would seem to be related to snoring, according to Gozal, because snoring causes the upper airways to contract, which makes the chest muscles work harder to pull in air, which in turn creates pressure on the airways and blood vessels, which causes blood to return to and dilate the heart. Then, too much fluid collects and needs to be released, which is one of BNP's functions -- to increase sodium and water excretion around the heart.

However, if snoring was responsible for the elevated BNP levels, a more serious snoring problem should have caused even higher levels of BNP, but that wasn't the case.

"Clearly, this is a complex mix," said Gozal.

What parents need to know from this study is that if your child is predisposed to bed-wetting, any additional factors, such a snoring, may make bed-wetting more likely. So, if your child snores and wets the bed, Gozal said that treating the snoring may help reduce bed-wetting.

"This is a great study, and it's nice to see some of the science behind the problem," said Dr. Sangeeta Chakravorty, clinical director of the pediatric sleep program at Children's Hospital of Pittsburgh.

"Parents should know that 15 percent of children get better every year with no intervention," she said, but added, if bed-wetting persists after a child is 5 years old and it happens more than three times a week, you should mention it to your child's doctor at the next well visit.

More information

To learn more about enuresis, visit the American Academy of Family Physicians.

SOURCES: David Gozal, M.D., professor, pediatrics, and director, division of pediatric sleep medicine, University of Louisville, Ky.; Sangeeta Chakravorty, M.D., clinical director, pediatric sleep program, Children's Hospital of Pittsburgh; May 2008 Pediatrics

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