Friday, July 11, 2008

New Clue Found In Cause Of SIDS

(previously published here at

Sudden Infant Death Syndrome (SIDS), the leading cause of death among infants younger than 1 year old, could result from a deficit imbalance of serotonin levels in the brain, according to a new study published in the July issue of the journal Science.

SIDS describes the sudden, unexplained death of an infant between 1 month and 1 year of age. Also called "crib death" since it often occurs while the infant is asleep, SIDS strikes many seemingly healthy infants and can only be diagnosed after ruling out all other possible causes. African Americans and Native Americans are two to three times more likely than Caucasians to die from SIDS, and boys are more often affected than girls.

Serotonin is a neurotransmitter - a signaling chemical - that affects brain and organ function throughout the body, influencing an individual's mood balance and playing a role in everything from depression, anger and appetite, to the regulation of body temperature, heart rate and arousal from sleep.

Dr. Cornelius Gross, Ph.D., and colleagues from the European Molecular Biology Laboratory near Rome, Italy, made the "chance discovery" of SIDS-like symptoms while attempting to determine serotonin's role in aggression and society. They observed that genetically engineered mice with abnormally low levels of serotonin experienced erratic drops in heart rate and a drop in body temperature. But it was after over half of the mice used in the study died, all before three months of age, that the scientists made the association between serotonin levels and SIDS.

Dr. Gross emphasized that the SIDS-like symptoms exhibited by the lab mice were not indicative of symptoms experienced by human infants who suffered from SIDS, since the mice had been engineered to have an overactive gene that inhibits serotonin production.

SIDS incidence rates peak at three to four months in babies born at full-term, and at around three to four months after the due date of babies born prematurely. This period is notable as the time around when infants can turn over by themselves while asleep, thus increasing the likelihood of putting their faces against soft material.

However, as noted by Dr. Gary Emmett, a general pediatrician with Jefferson University Hospital in Philadelphia, precautionary measures have cut the incidence rate in the U.S. by more than 50 percent in the past 20 years. According to the CDC and the National Center for Health Statistics, SIDS deaths are down from 1.43 deaths per live birth (1984) to 0.51 deaths per live birth (2005) - around 2,500 deaths annually.

The study's findings are far from being conclusive, it supports previous studies done by Dr. Hannah Kinney, from the Children's Hospital of Boston, where inadequate serotonin levels were linked to SIDS, but not in a way that could establish a method to measure risk or related symptoms.

Doctors and researchers hope that this connection might spur further awareness, interest and development into creating ways to screen infants for risk of SIDS.

"Now that [low serotonin levels has] come up as strongly related to two different species, we know we're on the right track [and] it'll encourage people to study this more in living human beings," said Dr. Emmett.

Referring to his study, Dr. Gross added that "Maybe there is some kind of signature we could find in these mice before they have a crisis, some way they respond when they wake up from sleep. That might help us identify those kids most at risk [for] SIDS and provide parents with some[thing] ... before a crisis occurs."

Heather Chin can be reached at

©The Evening Bulletin 2008

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