TUESDAY, July 31 (HealthDay News) -- A simple hearing test soon after birth may help identify babies at risk for sudden infant death syndrome (SIDS), a new U.S. study finds.

SIDS kills about one in 1,000 infants worldwide. Most of the victims are between two to four months old. Boys are more likely than girls to die of SIDS.

Dr. Daniel D. Rubens and colleagues at the Children's Hospital and Regional Medical Center, in Seattle, analyzed data on 31 Rhode Island babies who died of SIDS.

They found that they all shared the same distinctive difference in newborn hearing test results for the right inner ear.

Compared with other babies, those who died of SIDS scored four points lower in standard newborn hearing tests, across three different sound frequencies in the right ear.

Rubens also noted that healthy infants typically test stronger in the right ear than in the left. However, the infants who died of SIDS had lower scores for the right ear than the left.

The study was published in the July issue of the journal Early Human Development.

"This discovery opens a whole new line of inquiry into SIDS research," Rubens said in a prepared statement. "For the first time, it's now possible that with a simple, standard hearing test, babies could be identified as at risk for SIDS, allowing preventative measures to be implemented in advance of a tragic event."

The inner ear contains tiny hairs involved with both hearing and vestibular (balance) function. Vestibular hair cells may play an important role in transmitting information to the brain about levels of carbon dioxide in the blood, Rubens suggested. Injury to vestibular hair cells may disrupt respiratory control and predispose infants to SIDS.

Rubens urged further research in this area. "We must now fully explore all aspects of inner ear function and SIDS and analyze testing frequencies higher than those currently tested by newborn hearing screen centers," he said.

More information

The Nemours Foundation has more about SIDS.