Study Explains Infant Death

Sudden Infant Death Syndrome, the leading cause of death among infants less than 12 months old in the U.S. may be linked to low levels of serotonin in brain tissue, according to researchers at Harvard-affiliated Children’s Hospital Boston.

In infants under a year old, SIDS manifests as an unexpected and sudden death that cannot be explained by autopsy or death scene investigation. The study discovered that children who die from this syndrome exhibit abnormalities in brainstem control of autonomic functions, such as breathing and heart rate regulation.

“Many people initially thought SIDS only occurred because the baby stopped breathing during sleep,” said researcher Hannah C. Kinney, a professor of pathology at Harvard Medical School and a neuropathologist at Children’s Hospital.

“The implication here is that SIDS is an intrinsic problem in the brainstem and a biological problem that is not a mystery, but something that can be studied by scientific means.”

The researchers at Children’s Hospital analyzed the brain stems of infants that died of SIDS in comparison to the brain stems of children that died of other causes.

Using various molecular techniques, researchers examined tissue samples for markers of serotonin and other hormones.

“The most consistent abnormality that we have found in our research is in levels of serotonin,” Kinney said.

The investigators found that serotonin levels were 26 percent lower in the tissue samples collected from infants that died from SIDS. The levels of tryptophan hydroxylase, an enzyme needed to make serotonin, were also 22 percent lower.

While Kinney said that there are currently no specific tests to detect abnormalities in serotonin levels, she encouraged parents to continue to ensure that their children’s breathing is uninhibited during sleep in hopes of preventing SIDS.

—Staff writer Barbara B. DePena can be reached at barbara.b.depena@college.harvard.edu.