MONDAY, Jan. 20, 2003 (HealthDayNews) -- A new study bolsters a suspicion long held by scientists that sudden infant death syndrome (SIDS) has a genetic component.
Reporting in the American Journal of Medical Genetics, the researchers from Rush University explain that they found infants who died of SIDS were more likely to have a particular mutation in the 5-HTT gene. That gene regulates serotonin, one of the brain's chemical messengers that helps regulate breathing and heart rate.
"We pursued [this line of research] because we had too many parents coming to us saying they had done everything they had been told to do and their babies still died," says study author Dr. Deborah Weese-Mayer, a professor of pediatrics at Rush University and director of respiratory medicine at Rush Presbyterian St. Luke's Medical Center, both in Chicago.
Years of public education encouraging parents to stop smoking around their infants and to have babies sleeping on their backs has helped dramatically lower the rate of SIDS in the United States. Despite that decrease, 2,500 babies still die every year from this puzzling disorder, according to the U.S. Centers for Disease Control and Prevention.
Last year, a study published in Pediatrics reported that Japanese babies who died of SIDS were more likely to have an L allele in the 5-HTT gene than healthy babies. An allele is a mutation in the gene that can change physical characteristics.
Building on that research, Weese-Mayer and her colleagues collected DNA samples from 87 U.S. infants who died of SIDS and compared them to two sets of healthy infants. The first infant control group was matched as closely as possible to the gender and ethnicity of the SIDS babies. The second control group was a random group of 334 infants that the researchers used to determine the frequency of each allele in the general population.
As in Japan, the U.S. researchers found babies who died from SIDS were more likely to have the L allele in the 5-HTT gene than babies who survived. However, not every baby who had the L allele died from SIDS. Likewise, not all of the babies who died from SIDS had the L allele. The researchers also found healthy babies were more likely to have an S allele in the 5-HTT gene than babies who died of SIDS.
Weese-Mayer says the researchers were also able to pinpoint ethnic differences in this gene. Black babies were more likely to have the L allele than white babies were, which is important because black babies have a much higher rate of SIDS.
While this means the researchers have shown there can be a genetic underpinning to SIDS, there is still much research that needs to be done before a screening test to identify high-risk babies can be developed.
"This is a hypothesis we've been testing, and it's exciting to have it suddenly appear, but it's not a magic bullet," Weese-Mayer says. "There are other genes we're looking at, and I think the profile we're looking for will be a composite of genes."
She's also quick to point out that modifying the environmental factors will always be an important part of keeping the incidence of SIDS down. "Smoking is huge! Avoid cigarette smoking, both [prenatal] and postnatal. And that advice isn't just for mom. No one should smoke around pregnant women or babies," Weese-Mayer says.
Dr. Susanna McColley, acting division head of pediatric pulmonary medicine at Children's Memorial Hospital in Chicago, says it's important that people realize the researchers haven't found the SIDS gene. "You would find a lot of healthy kids with this allele," she says.
While she says this research needs to be validated in further studies, she says it "may allow us to see which kids will remain at high risk even when environmental risk is reduced."
More information
For information on lowering your child's risk of SIDS, visit the American SIDS Institute or the SIDS Alliance.
