Possible Cause for Sudden Infant Death Syndrome Discovered

(Ivanhoe Newswire) -- Brain abnormalities may be the cause of sudden infant death syndrome -- the number one cause of death in infants between 1 month and 1 year of life.

Sudden infant death syndrome, or SIDS, is the unexpected death of an infant whose death remains unexplained after all attempts, including an autopsy, have been made to find a cause. Researchers now believe this mystery has a concrete biological basis.

In a typical situation, the mother or father puts their apparently healthy baby down for a nap or for the night and returns to find the baby dead. Since the medical community cannot tell the parents why their baby died, they often blame themselves or each other. This often results in even greater tragedy, according to the American SIDS Institute.

Putting infants to sleep on their stomachs is a well-identified risk factor. Sixty-five percent of the SIDS infants evaluated in this study were found sleeping on their stomach or side during the time of death. Now, researchers have documented abnormalities in the brain stem of babies who have died from SIDS.

Doctors from Children's Hospital Boston and Harvard Medical School examined brain autopsy specimens from 31 infants who died from SIDS and 10 who died from other causes. After examining the lowest part of the brainstem -- the medulla oblongata -- they found abnormalities in nerve cells that make and use seratonin.

The brainstem seratonin system is thought to help coordinate breathing, blood pressure, sensitivity to carbon dioxide, and temperature. When babies sleep face down, it is believed they breathe in exhaled carbon monoxide; taking in less oxygen. The rise in carbon dioxide activates nerve cells in the brainstem so the baby doesn't asphyxiate.

But researchers believe that babies who die from SIDS have defects in their seratonin system, which impairs their reflex to wake up and turn over.

Defects that been identified are:

Deficiencies in a seratonin receptor called 5HT1A
An abnormally high number of neurons that make and release serotonin
Insufficient amounts of a seratonin transporter protein

This new data may explain why SIDS occurs twice as often in males then females -- male SIDS infants have fewer 5HT1A receptors than females SIDS infants.

Researchers hope to develop a diagnostic test to identify infants at risk for SIDS. They also hope to develop a drug or treatment to protect infants who have abnormalities in their brainstem seratonin system.

This article was reported by Ivanhoe.com, who offers Medical Alerts by e-mail every day of the week. To subscribe, go to: http://www.ivanhoe.com/newsalert/.

SOURCE: The Journal of the American Medical Association, 2006;296:2124-2132