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"Long
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September 11, 2007
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Mystery of sudden infant deaths may be solved: researchers
Nov. 8, 2006
Special to World Science
“Sudden infant death syndrome” may result from abnormalities in the brain
stem, a
primitive brain region that regulates basic life functions, a study has found. Cross-section of the
brain stem, a stemlike region that joins the spinal cord to the main bulk
of the brain, in SIDS infants (above) and normal ones (below). SIDS
babies were found to have more cells that make and release serotonin,
particularly in
an area known as the midline raphé nucleus
(blue dots). But the
SIDS infants also had insufficient amounts of two substances that
facilitate serotonin use, researchers
said. (Image courtesy David Paterson, Ph.D., Children’s Hospital Boston)
The syndrome, abbreviated SIDS, is the sudden and unexpected death of infants under a year old, who are typically found to have died in their sleep with
no signs of suffering. An enigmatic condition, it strikes 15 of every 10,000 babies, according to the
Merck Manual of Diagnosis and Therapy.
The new findings suggest it “is not a mystery but a disorder that we can investigate with scientific methods, and some day, may be able to identify and treat,” said Hannah Kinney of Children’s Hospital
Boston and Harvard Medical School in Boston, the study’s lead author.
The research appeared in the Nov. 1 issue of the Journal of the American Medical Association.
The brain stem controls heart rate, breathing, blood pressure, temperature and arousal. The abnormalities that Kinney and colleagues
identified seem to affect its ability to use the brain chemical serotonin, they
said.
Serotonin plays roles in communication between brain cells and in
regulating mood, breathing and blood pressure.
The findings suggest the risk of sudden infant death “may greatly increase when an underlying predisposition combines with an environmental risk,” said Duane Alexander, director the National Institute of Child Health and Human Development of the National Institutes of Health, which funded the study.
The chief environmental risk to which Alexander referred was sleeping face down, a recognized
SIDS risk factor.
The researchers compared the brainstems of 31 SIDS victims and 10 infants who died of other causes.
The scientists found that victims’ brainstems have less of two substances that
facilitate serotonin use, compared to the number of cells that use it. These
enablers of serotonin use are called the serotonin transporter
protein
and the serotonin receptor 5HT1A.
The result seems to be a shortage of useable serotonin, which changes babies’ reactions, the scientists argued.
When babies sleep face-down or have their faces covered by bedding, they are thought to re-breathe exhaled carbon dioxide,
and thus
get less oxygen. Normally, the rise in carbon dioxide activates nerve cells in the brainstem,
the researchers said. These in turn stimulate a reaction that prevents asphyxiation.
“A normal baby will wake up, turn its head, and start breathing faster,” said Kinney.
In sudden infant death victims, defects in the serotonin system may impair these reflexes,
with tragic results, she added.
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“Sudden infant death syndrome” may result from abnormalities in the brainstem, a part of the brain that helps control basic life functions, a new study has found. The syndrome, abbreviated SIDS, is the sudden and unexpected death of infants under a year old, who are typically found to have died in their sleep with signs of suffering. It strikes 15 of every 10,000 babies, according to the Merck Manuals Online Medical Library. The new findings suggest it “is not a mystery but a disorder that we can investigate with scientific methods, and some day, may be able to identify and treat,” said Hannah Kinney of Children’s Hospital Boston and Harvard Medical School in Cambridge, Mass., the study’s lead author. The research appeared in the Nov. 1 Journal of the American Medical Association The brainstem controls heart rate, breathing, blood pressure, temperature and arousal. The abnormalities that Kinney and colleagues found appear to affect its ability to use the brain chemical serotonin, they said, which plays roles in communications between brain cells and in regulating mood, breathing and blood pressure. The finding suggests the risk of sudden infant death “may greatly increase when an underlying predisposition combines with an environmental risk,” said Duane Alexander, director the National Institute of Child Health and Human Development at the of the National Institutes of Health, which funded the study. The chief environmental risk to which Alexander referred was sleeping face down, a recognized risk factor for SIDS. The researchers compared the brainstems of 31 SIDS victims and 10 infants who died of other causes. The scientists found that victims’ brainstems have less of a substance that enables serotonin to be used—called serotonin transporter protein—compared to the number of cells that use serotonin. The result seems to be a serotonin shortage that changes babies’ reactions, the scientists argued. When babies sleep face-down or have their faces covered by bedding, they are thought to re-breathe exhaled carbon dioxide, therefore breathing in less oxygen. Normally, the rise in carbon dioxide activates nerve cells in the brainstem, which in turn stimulates a reaction that prevents asphyxiation. “A normal baby will wake up, turn its head, and start breathing faster,” said Kinney, but in sudden infant death victims, defects in the serotonin system may impair these reflexes.