SIDS Linked to Brain Defect

A new study has found that babies at risk of sudden infant death syndrome (SIDS) are born with abnormalities in the brainstem.

Researchers from Children's Hospital Boston (MA, USA) and Harvard Medical School (Boston, MA, USA) examined frozen medullae from 31 infants who died from SIDS and 10 controls who died from other causes, obtained from the San Diego (CA, USA) medical examiner's office between 1997-2005. The researchers found that medullary serotonin-using neurons exhibited an extensive pathology in SIDS, potentially including abnormal neuron firing, synthesis, release, and clearance. The research suggested that the brains of SIDS babies contained an abnormal level of serotonin, though it was not clear whether it was more or less.

Medullary serotonergic neurons in the medulla oblongata project extensively to autonomic and respiratory nuclei in the brainstem and spinal cord and help regulate homeostatic function. Although the brainstem tissue from the SIDS infants contained more neurons, they appeared to contain fewer receptors for serotonin than did the brainstems of control infants. Male SIDS infants had fewer serotonin receptors than did either female SIDS infants or control infants, a finding that may provide preliminary neurochemical evidence explaining the increased vulnerability of boys to SIDS. The study was published in the November 1, 2006, issue of the Journal of the American Medical Association (JAMA).

"Our hypothesis right now is that we're seeing a compensation mechanism,” said co-author Dr. David Paterson, Ph.D. "If you have more serotonin neurons, it may be because you have less serotonin and more neurons are recruited to produce and use serotonin to correct this deficiency.”

Every year, about 2,000 seemingly healthy babies in the United States die of SIDS, or crib death. Studies have shown that infants who sleep on their stomachs are at higher risk of dying. The "Back to Sleep” campaign sponsored by the U.S. National Institutes of Health (NIH), which urges parents to place infants to sleep on their backs, has helped to reduce the number of deaths by 50% since 1994. Despite this, 65% of SIDS infants in the study were found to be sleeping on their stomachs or sides.



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Children's Hospital Boston
Harvard Medical School