Approximately 2,500 babies die of SIDS each year in this country, thousands more throughout the world. Most of these deaths happen between the ages of 2 and 4 months old. On Tuesday, the Journal of the American Medical Association published on study that offers one explanation as to why babies may suddenly die.
It is one of the most devastating experiences a family can go through, their baby dying in his or her sleep, suddenly and mysteriously.
Mary McClain counsels such families at the Boston University Medical Center.
"Parents, more than anyone else, want answers as to what happened to their baby, what caused their baby to die," she said.
But there are no known causes, until now.
The new study says it's a problem deep inside a baby's brain, in the brainstem.
"This is where we have found the major problem in SIDS, although we have looked at all levels of the brainstems, the major problems are here," Dr. Hannah Kinney said.
Researchers do know that sleep position is important. All babies need to be put to sleep on their back, and that is a very important way to lower a baby's risk of SIDS.
And what the new study reveals may explain why that's important.
Dr. Kinney and her co-authors reviewed autopsy results of SIDS and non-SIDS deaths. They discovered that SIDS babies had lower levels of the chemical serotonin and other related chemicals in their brainstems.
This is in regions of the brainstem that control breathing and heart rate and blood pressure during sleep. Doctors have been telling parents to put babies to sleep on their back. Always. That is a very important way to lower a baby's risk of SIDS.
And what the new study reveals may explain why that's important. A baby that is face down on a bed or with its face in pillows may begin to re-breathe carbon dioxide, which is toxic.
"A normal baby could respond to that challenge, lift its head up, turn its head and arouse or wake up," Dr. Kinney said. "When a baby who has a defect in those brain stem circuits that use serotonin can't do that when challenged, and they go on to die."
This step may help move along research that could one day possibly identify babies that are at higher risk of SIDS. For the time being, parents need to follow SIDS prevention advice, with no pillows in the crib and babies sleeping only on their backs.