Researchers at Children’s Hospital Boston and Harvard Medical School have found new evidence that sudden infant death syndrome (SIDS) is related to abnormalities in nerve cells in the brain stem, unraveling more about an elusive disease whose cause has been shrouded in mystery.

According to a National Center for Health Statistics study, in 2002, SIDS was the third leading cause of infant death in the U.S., accounting for eight percent of the infant mortality rate. More than 57 children die of SIDS out of every 100,000 live births.

The new research gives a biological basis for “all the risk-reduction strategies” that currently exist for SIDS, including having children sleep on their back, said David S. Paterson of Children’s Hospital Boston and a co-author of the study.

“The brain stem works as an alarm, a kind of control and integration center, for determining physiological changes in the body... if the system is defective and you’re lying face down, you will die,” he added.

Cathy Spong, chief of the pregnancy and perinatology branch at the National Institute of Child Health and Human Development (NICHD), said the results of the study explain why the NICHD’s campaign to have healthy babies sleep on their back has worked. According to Spong, the program has led to a decrease in the SIDS rate by twofold since its inception in 1994.

Spong also emphasized the sentimental significance of the study. “One of the hugest problems with SIDS is that it’s difficult for families [with victims of SIDS], because they have no reason for why the baby died,” she said. “What this study provides is a possible reason, so you can allow [them] at least to have some closure, [to know] that it wasn’t something that they did.”

Paterson also mentioned that the Dartmouth College of Medicine, Yale University, Columbia University, and the Children’s Hospital in San Diego are collaborating to develop a diagnostic test for babies at high risk of contracting SIDS, building off his recent research.

But he warned against being too optimistic. “In terms of how close we are to that, it’s going to be a long time, years, maybe tens of years,” he said, adding that “a treatment would be even further down the line.”

The study appeared in the Nov. 1 issue of the Journal of the American Medical Association.

—Staff writer Yifei Chen can be reached at chen13@fas.harvard.edu.