Study links SIDS to brain chemical defect

In a small study with big implications, researchers found some of the strongest evidence yet that sudden infant death syndrome -- a medical and sometimes legal mystery once known as crib death -- may be caused by abnormalities in the brain stem.

The finding “takes the mystery away from SIDS,” said Marian Willinger, a SIDS researcher at the National Institute of Child Health and Human Development, which funded the study. “It should take the guilt away from any parent who has lost a baby, because they always wonder ‘What did I do wrong?’ Now they need to really understand: ‘My baby had a disease.’ ”

The brain-stem abnormalities involve an imbalance in the way the brain uses the neurotransmitter serotonin. The brain chemical, which plays a role in regulating mood and is the target for many depression-fighting drugs, also influences breathing, body temperature and arousal from sleep.

These functions are thought to go awry when susceptible babies are exposed to certain risks, such as sleeping on their bellies, a leading contributor to SIDS.

The researchers, who published their findings Wednesday in the Journal of the American Medical Assn., studied autopsied brain tissue from 31 SIDS babies and 10 infants who died of other causes. SIDS babies had about double the number of nerve cells displaying serotonin defects.

Right now, the defects cannot be detected until after death.

The researchers hope their work will lead to a diagnostic test that could identify infants at risk and allow parents to take precautions.