Solving SIDS: The Serotonin Connection

A new study found low levels of serotonin in the brain tissue of infants who died from SIDS. The study suggests that a brain defect may cause some babies to be more vulnerable to sudden death while they sleep.

The results were published today in JAMA.



The autopsy analysis involved 35 infants who died from SIDS. They were compared with five infants who died from known causes.

Researchers examined small samples of tissue from the medulla. This is a region at the base of the brain. It regulates basic functions such as body temperature, breathing, blood pressure and heart rate.

Results show that serotonin levels were 26 percent lower in SIDS cases than in controls. Serotonin is a brain chemical that helps regulate mood. It also plays a role in regulating vital functions like breathing and blood pressure.

Measurements of “tryptophan hydroxylase” also were 22 percent lower in SIDS infants. This is an enzyme that is needed to make serotonin.

The authors suspect that this defect may hinder an infant’s capacity to respond to breathing challenges. As a result the child may inhale carbon dioxide that was exhaled while sleeping face down.

"Our research suggests that sleep unmasks the brain defect," senior author Dr. Hannah C. Kinney said in an NIH news release. "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."

Kinney hopes that a test will be developed to detect the abnormality. Steps could be taken to protect the infants who are most vulnerable.

She also said parents should continue to follow the Back to Sleep tips for safe infant sleep.

"Until 12 months of age, babies should sleep on their backs in a crib with a firm mattress, and without toys, soft pillows, excessive blanketing or excessive clothing," she told AFP.

An earlier study led by Kinney involved 31 infants who died of SIDS. The brainstems from SIDS infants contained more neurons that make and use serotonin. This suggested that the brain was compensating for low levels of serotonin.

Read more about sleep and infants and SIDS.

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Infant Sleep: SIDS & Crib Safety

A new study examined trends and factors associated with infant sleeping position.

The study analyzed telephone surveys from 1993 through 2007. Each year’s survey involved nighttime caregivers of infants born within the last seven months. They were asked, “Do you have a position you usually place your baby in?”

Results show that the proportion of babies placed to sleep on their backs steadily increased between 1993 and 2001. But there was no change after 2001.

Maternal concerns about infant comfort and choking reduced the rate that infants were placed to sleep on their backs. Caregivers were more likely to put infants to sleep on their backs if they were advised to do so by a doctor.

“Placing infants on their backs for sleep remains the single most effective means we know to reduce the risk of sudden infant death syndrome," Marian Willinger, PhD, said in a NIH news release. She is the special assistant for SIDS research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The NICHD funded the analysis.

In 1994 the NICHD launched the “Back to Sleep” campaign. It urges parents and caregivers to place infants to sleep on their backs.

The NICHD reports that the rate of infant back sleeping has increased from roughly 25 percent to about 70 percent. At the same time, the SIDS rate has decreased by more than 50 percent.

Last month the U.S. Consumer Product Safety Commission announced the voluntary recall of more than 2.1 million drop-side cribs made by Stork Craft. This included about 147,000 cribs with the Fisher-Price logo. The cribs were sold at major retailers such as Sears and Wal-Mart.



There have been 110 reported incidents of drop-side detachment in the U.S. and Canada. These included 15 entrapments and 20 falls from the crib. Four of the entrapments resulted in suffocation. Fall injuries ranged from concussion to bumps and bruises.

Consumers can contact Stork Craft to receive a free repair kit. It allows you to convert the drop-side on these cribs to a fixed side. Parents and caregivers are urged to stop using the recalled cribs until the repair is made.

Contact Stork Craft toll-free at (877) 274-0277 anytime to order the free repair kit. You also can go online to www.storkcraft.com. For more information on Crib Safety, visit the CPSC's Crib Information Center.

Earlier this year the Sleep Education Blog reported that babies should never be put to sleep in a car safety seat. Learn more about sleep and infants & toddlers.

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