Children's Health: The Deadly Secrets of Sudden Infant Death Syndrome
Sudden infant death syndrome, better known as SIDS, is a cruel killer, striking seemingly healthy infants as they sleep. Scientists have been struggling for decades to discover why some 2,100 babies die of SIDS each year. It's the leading cause of infant death in the United States. Now, doctors say, they have unearthed the strongest evidence yet that a region in the brain that controls breathing is abnormal in infants who die of SIDS.
For a study published in today's Journal of the American Medical Association, a group of researchers in Massachusetts and California looked at the brains of 31 infants in San Diego who died of SIDS and 10 who died of other causes. They focused on the medulla, an area in the brain stem that controls involuntary actions like breathing, blood pressure, and heart rate that has been the focus of much SIDS research. They found that the SIDS babies were far more likely to have abnormal neurons and abnormal serotonin receptors in the medulla than non-SIDS babies. The abnormalities were more extensive than those found in earlier studies. What's more, the SIDS baby boys in the study had fewer neurotransmitter receptors than the SIDS girls, which may help explain why boys are twice as likely to die of SIDS than girls.
No one knows what causes the abnormalities in SIDS-prone babies. Hannah Kinney, an associate professor of neuropathology at Children's Hospital Boston and co-author of the JAMA study, thinks the abnormalities develop in utero. Other researchers disagree, and are looking for birth stresses or environmental factors in early life that could account for the problem. Kinney thinks that in the end, developmental problems like she has found as well as genetic and environmental influences will be involved. And although more than half the SIDS babies in the JAMA study had brain-stem abnormalities, 48 percent did not. Researchers say SIDS will almost certainly end up being a collection of syndromes, with some caused by brain dysfunction and others by heart arrythmias or other as-yet-unrecognized problems.
Kinney, who has been trying to solve the SIDS mystery since the early 1980s, says that her group's findings reinforce the American Academy of Pediatrics' 14-year-old "Back to Sleep" program. It aims to reduce the risk of SIDS by telling parents and caregivers to put infants to sleep face up, and to keep soft bedding like quilts and pillows out of the baby's crib. A child without the brain abnormalities would have no problem sleeping face down, but a SIDS-prone child might.
"We feel that this kind of biological data gives an explanation to the 'Back to Sleep' messages, which might seem a little crazy at first blush," Kinney says. "Why would putting a baby on its back save a life?" If that baby has a defect in its brain arousal system, it might asphyxiate if laid face down. "A normal baby would sense the low oxygen and turn its head and wake up."