A collection of genes involved in early development may help explain why black babies are more at risk of sudden infant death syndrome than other U.S. groups, researchers said on Thursday.

The gene mutations may also help explain why thousands of U.S. infants still succumb each year to SIDS, also known as crib death or cot death, despite education campaigns that have cut the rate in half, the researchers said.

Dr. Debra Weese-Mayer, a professor of pediatrics at Rush University Medical Center in Chicago, said the finding does not fully explain the unexpected deaths of 3,000 U.S. infants a year, but helps explain some of the underlying biology.

“For years everyone said SIDS was a mystery, but to me it is a puzzle and each of our studies fits in another piece,” Weese-Mayer said in a telephone interview. “This is one more critical piece of information that tells us we are on the right path.”

Writing in the September issue of Pediatric Research, Weese-Mayer and colleagues at the University of Pittsburgh and elsewhere said they compared genetic material from 92 SIDS cases to that of 92 healthy 1-year-olds.

They looked specifically at genes involved in the development of the autonomic nervous system, which controls breathing, heartbeat and other involuntary functions.

“If you have dysregulation of the autonomic nervous system, possibly in a stressful situation you don’t have resiliency,” she said. Heart rate and breathing may not be able to adapt quickly and may simply shut down - which is what happens to SIDS babies.

SAME MUTATION

The researchers found 11 different mutations in 14 of the 92 SIDS cases but only one mutation - the same one - in two of the 92 healthy babies.

“The curiosity is that 71 percent of the SIDS cases that had the mutation were African-American and both controls (healthy babies that had it) were African-American,” she said.

“Knowing that the SIDS incidence is significantly higher in African-Americans gives strong support for the possibility of a genetic basis.”

Other researchers have found different genes that may be involved in SIDS.

In July a team at the Translational Genomics Research Institute in Phoenix, Arizona, found a new disorder in Amish families from Pennsylvania that causes sudden infant death and sometimes malformation of the genitals.

In 2000 and 2001 researchers in the United States and Japan found a role for the serotonin transporter gene promoter in the brainstems of SIDS victims.

While SIDS is a general term for unexplained infant deaths, doctors suspect a variety of causes. U.S. and British campaigns to teach parents and caretakers to have babies sleep on their backs cut SIDS deaths in half, but did not eradicate them.

“We have had too many parents who came to us and said ‘look, we did everything right - we got the best prenatal care, no one smoked anywhere near the baby, we never put her down on her tummy and still she died’,” Weese-Mayer said. “That led us to say there has to be a genetic basis.”

The tissue from the SIDS babies was donated anonymously, so Weese-Mayer says she cannot tell if the gene mutations her team found run in families. She hopes the government might sponsor a large study to see how common the genetic mutations are in the population as a whole.

That will help determine whether the mutations actually cause SIDS, she said.

SOURCE: Pediatric Research, August 2004.