Sudden Infant Death Syndrome (SIDS) is the leading cause of death in babies in the first year of life. It is responsible for about 2,000 infant deaths in the United States according to the CDC.

Now, there may be hope for solving the mystery over why the deaths occur.

Researchers at Boston Children’s Hospital have found many babies that die “suddenly and unexpectedly” have “underlying brainstem abnormalities and are not all normal prior to death.”

The hospital published its findings in the December issue of Pediatrics.

“These abnormalities impair brainstem circuits that help control breathing, heart rate, blood pressure and temperature control during sleep,” the hospital wrote in a press release on the finding of neuropathologist Dr. Hannah Kinney and her team. “The researchers believe [the abnormalities] prevent sleeping babies from rousing when they rebreathe too much carbon dioxide (due to inadequate ventilation), breathe too little oxygen or become overheated (from overbundling).”

Here is an excerpt from the hospital’s press release:

In the new study, Kinney and colleagues asked if all these infants are truly normal. They reexamined their data, reviewing the cases of 71 infants who died suddenly and unexpectedly, were autopsied at the San Diego County Medical Examiner’s office from 1997 to 2008, and had brainstem samples available for analysis. The researchers grouped the infants according to sleep circumstances—those that were considered likely to generate asphyxia and those that were not—based upon death-scene investigation reports.

In the end, they compared 15 infants with SIDS whose deaths were deemed not to involve asphyxia (group A), 35 SIDS infants whose deaths were possibly asphyxia-related (group B) and 9 infants who clearly died from other causes (controls). They excluded the other infants, who either had insufficient data or had evidence of other clear risk factors for death, such as exposure to drugs or extremes of temperature.

Brainstem neurochemical abnormalities—involving serotonin, serotonin receptors, GABA receptors and 14-3-3 (a protein that regulates serotonin)—were found in both group A and group B. Infants in these two groups—with and without environmental risk factors for asphyxia—had the same brainstem abnormalities, and both groups differed significantly from the controls.

“Even the infants dying in a potentially asphyxia-generating situation [sleeping face down or next to an adult] had an underlying brainstem abnormality that likely made them vulnerable to sudden death if there was any degree of asphyxia,” Kinney said. “The abnormality prevents the brainstem from responding to the asphyxial challenge and waking.”

The investigators believe these findings confirm that sudden unexplained death in infants is associated with underlying vulnerabilities, and that not all infants who die in compromised sleep environments are normal.

“Certainly, there are compromised sleeping environments that can cause any baby to die, such as entrapment in the crib, but if it’s just sleeping face down, the baby who dies may have an underlying brainstem vulnerability,” Kinney said. “We have to find ways to test for this underlying vulnerability in living babies and then to treat it. Our team is focused now upon developing such a test and treatment.”

Dr. Kinney said following “safe sleep practices” remained “absolutely important” to prevent babies from “potentially asphyxiating” situations.

