Researchers Find Possible Cause for SIDS

Sudden infant death syndrome (SIDS) is the leading cause of death among babies in their first year, and to prevent this health experts have been urging new parents to put infants to sleep on their backs.

Now new research has pinpointed a possible biological cause for SIDS, along with findings that most infants who succumb to SIDS were found on their stomachs or sides in spite of a public awareness campaign that warns against this.

Researchers at Children's Hospital in Boston believe abnormalities in the production and use of the brain chemical serotonin - which is believed to regulate breathing, blood pressure, body heat and the ability to wake - could be the cause of SIDS.

Led by neuropathologist Hannah Kinney, M.D., and neuroscientist David Paterson, Ph.D., the researchers examined autopsy data from 31 infants who had died of SIDS and 10 who had died of other causes. They found abnormalities in the nerve cells that make and use serotonin in the brainstems of the SIDS babies. The chemical's action would cause a normal baby to wake, turn his head and start breathing faster if his face was covered by bedding and he was breathing in too much carbon dioxide. A baby with the abnormalities might not wake, and thus asphyxiate.

The researchers believe that the abnormalities begin during early fetal development, and that smoking or alcohol use on the part of the mother could be contributing factors.

The findings, published in a recent issue of the Journal of the American Medical Association (JAMA), also help explain why current advice about putting babies to sleep on their backs to prevent SIDS seems to work. Since babies with serotonin abnormalities might have trouble waking, putting them to sleep on their backs on firm bedding puts them in the best position to have a good oxygen supply and avoid re-breathing carbon dioxide that becomes trapped in bedding.

But while the national Back to Sleep campaign is credited with reducing SIDS cases by 50 percent since 1995, the researchers say that about 65 percent of SIDS victims in their study were found sleeping on their stomachs or sides. The researchers hope their findings will one day lead to a diagnostic test to identify babies at risk of SIDS, and even a treatment to protect those babies with serotonin abnormalities.

- Christina Elston