Low levels of serotonin linked to sudden infant death syndrome

Washington, Feb 3 (ANI): Scientists have found a link between low levels of serotonin - a brain chemical that conveys messages between cells - and sudden infant death syndrome (SIDS).

They found that the brains of infants who die of SIDS produce low levels of serotonin, a brain chemical that conveys messages between cells and plays a vital role in regulating breathing, heart rate, and sleep.

The researchers theorize that this newly discovered serotonin abnormality might reduce infants' capacity to respond to breathing challenges, such as low oxygen levels or high levels of carbon dioxide.

These high levels may result from re-breathing exhaled carbon dioxide that accumulates in bedding while sleeping face down.

"We have known for many years that placing infants to sleep on their backs is the single most effective way to reduce the risk of SIDS," said Dr Alan E. Guttmacher, acting director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the NIH institute that funded the research.

"The current findings provide important clues to the biological basis of SIDS and may ultimately lead to ways to identify infants most at risk as well as additional strategies for reducing the risk of SIDS for all infants," Guttmacher added.

The research team led by senior author Dr Hannah C. Kinney, of Harvard Medical School and Children's Hospital Boston examined small samples of tissue from the medulla, a region at the base of the brain that regulates basic functions such as body temperature, breathing, blood pressure, and heart rate.

They analyzed brain tissue from infants who died from SIDS and controls who died of other causes.

The study showed serotonin levels were 26 percent lower in tissue from infants who died of SIDS than in tissue from the group of infants who had otherwise died unexpectedly.

The measurements of tryptophan hydroxylase, an enzyme needed to make serotonin, also were 22 percent lower.

"Our research suggests that sleep unmasks the brain defect," Kinney said.

"When the infant is breathing in the face-down position, he or she may not get enough oxygen. An infant with a normal brainstem would turn his or her head and wake up in response. But a baby with an intrinsic abnormality is unable to respond to the stressor

"It's no one single factor but a culmination of abnormalities that result in the death. In fact, in 88 percent of the SIDS cases they examined, the researchers found two or more risk factors, such as the infant's sleep position, an illness, or exposure to cigarette smoke," Kinney added.

Kinney hopes these findings will one day lead to a test that measures infants' serotonin levels in the blood or other tissues that reflect brain serotonin levels.

Such a test might make it possible to identify those at the highest risk for SIDS so that additional steps could be taken to protect them.

he findings appear in The Journal of the American Medical Association. (ANI)