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Researchers find link between serotonin levels and SIDS

By Jed Boal | Posted - Feb. 2, 2010 at 6:55 p.m.



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MIDVALE -- Boston researchers published a study that shows SIDS babies have decreased levels of serotonin in their brain stems. This could lead to a biological basis for placing babies on their backs in bed.

Sudden Infant Death Syndrome, or SIDS, is the leading cause of unexpected death in babies 1 month to 1 year old. A new study discovered decreased levels of a critical chemical in the brain stems of SIDS babies.

**What is … Sudden Infant Death Syndrome?**
SIDS is the sudden, unexplained death of an infant younger than one year old. It is the leading cause of death in children between one month and one year of age. Most SIDS deaths happen when babies are between 2 months and 4 months of age. *-[CDC, National Institute of Child Health and Human Development](http://www.nichd.nih.gov/health/topics/Sudden_Infant_Death_Syndrome.cfm)*
Serotonin is a chemical that helps regulate breathing, blood pressure and heart rate in the brain during sleep. A study out today in the Journal of the American Medical Association shows SIDS babies had lower levels of serotonin in their brain stems.

KSL talked with pediatrician Dr. Jeffrey Cline at Greenwood Health Center in Midvale as he was checking little Zoe Bradbury. Zoe is a happy, healthy 9-month-old baby. But, too many of her peers will not survive infancy because of Sudden Infant Death Syndrome.

Dr. Cline has not read the study, but he's eager to hear about promising research.

"I don't think anybody has classified exactly what the underlying circumstances are that lead to SIDS. So, that is the first fundamental step in identifying the problem before you can work towards treating it," Dr. Cline says.

**Keeping baby safe**
![](http://media.bonnint.net/slc/1753/175382/17538293.jpg)• Always place babies on their backs to sleep • Place your baby on a firm sleep surface, such as a safety-approved* crib mattress covered with a fitted sheet • Keep soft objects, toys, and loose bedding out of your baby's sleep area • Avoid letting your baby overheat during sleep • Think about using a clean, dry pacifier when placing your baby down to sleep *-CDC, National Institute of Child Health and Human Development*
Dr. Hannah Kinney of Children's Hospital Boston and other researchers found a link with serotonin.

"We found that the babies who died of SIDS had abnormalities in serotonin in regions of the brain stem that control breathing and heart rate and blood pressure during sleep," Dr. Kinney says.

The researchers suggest that if a baby is put face down in the bed, it begins to re-breathe toxic carbon dioxide. A normal baby could lift its head and wake up. But, a baby with a defect in brain stem circuits that use serotonin cannot do that, and dies.

"So, if you have a deficiency in these serotonin pathways that regulate vital functions during sleep and in response to challenges, an infant may go on to die during sleep," says Dr. Kinney.

Dr. Kinney and co-authors reviewed autopsies of SIDS babies and babies who died from known causes. The study appears in Journal of the American Medical Association. It shows SIDS babies had lower levels of serotonin and related chemicals in their brain stems. There was a 26 percent decrease in the level of serotonin and a 22 percent decrease in the level of tryptophan hydroxylase, the enzyme that makes serotonin. Also, they showed more than 50 percent decreases in receptors in different regions of the medulla of the brain stem.

**What is… serotonin?**
Serotonin is a neurotransmitter , a type of chemical that helps relay signals from one area of the brain to another. It helps regulate mood, appetite, sleep, muscle contraction, memory, learning and temperature.
Dr. Cline hopes ongoing research like this eventually leads to solutions and answers for parents.

"SIDS doesn't really give us that," says Cline. "It says that we don't really know. We've looked at a lot of other reasons, and we still aren't able to tell you exactly what happened to your child. It's very frustrating."

Dr. Cline says regulating serotonin in babies would be a very distant step, even if the cause were conclusive.

Researchers say the study findings may give a biological basis for infants to be put to sleep on their backs. That's what pediatricians recommend.

If you're concerned about SIDS risk factors, talk to your pediatrician.

E-mail: jboal@ksl.com

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Jed Boal

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