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.

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.

Do Ads Influence How Babies Sleep?

A new study in Pediatrics found that more than one-third of photographs in advertisements and articles in magazines geared toward women, expectant parents, and parents of young children show babies sleeping on their sides or stomachs, and nearly two-thirds of the pictures show infant sleep environments that increase risk for sudden infant death syndrome (SIDS).

Pictures that show babies sleeping on their side or stomach create confusion about infant sleep and may lead to unsafe practices.

A total of 391 unique pictures from 34 magazine issues were analyzed for sleep positions, including whether or not the baby was placed on its side or stomach rather than on its back, as well as dangers in infant sleeping environments, including soft bedding. Only 36 (36.4%) pictures showed infants sleeping in safe environments.

Of 122 pictures of infants sleeping, only 64% showed the babies sleeping on their backs. Compared with pictures accompanying news articles, photos in advertisements were more likely to show babies sleeping on their sides or stomachs (39% versus 27%).

To reduce the risk of SIDS, the AAP recommends that babies sleep separately from their parents and be placed in a crib on their backs, without blankets, pillows, or other soft bedding. Soft and loose bedding increases the risk of SIDS about five-fold overall and 21-fold when babies are also sleeping on their stomachs, according to the researchers.

Learn more about SIDS on SleepEducation.com.

Co-sleeping, Bed Sharing & Infant Deaths

A new study reports that infant mortality rates attributable to accidental suffocation and strangulation in bed have quadrupled since 1984. The rates of these deaths increased from 2.8 to 12.5 deaths per 100,000 live births from 1984 to 2004.

Why the dramatic increase? The Washington Post reports that it could be an issue of data shifting.

There are stricter guidelines for sudden, unexpected infant deaths. As a result these deaths are being classified more carefully. Some deaths once classified as SIDS may now be classified as suffocation.

There also may be a link to a recent rise in co-sleeping and bed sharing. Another article in the Washington Post reports that bed sharing in the U.S. doubled from 1993 to 2000.

In one Georgia county three infants recently suffocated in bed. In each case reports indicate that a parent rolled onto the child while sleeping.

A recent study found a bed-sharing rate in the U.S. of 42 percent when infants are 2 weeks old. The rate was 34 percent at 3 months of age and 27 percent at 12 months.

Bed-sharing rates are much higher in some other cultures. In one study about 61 percent of Thai infants shared the bed with their parents.

A common reason for bed sharing is to make it easier to breastfeed. A study found that bed-sharing infants breastfeed longer and more often.

But research also has linked co-sleeping to an increased risk of infant death. One study found that the risk is highest with couch sharing. It also found a higher risk of death for bed-sharing infants who are less than 11 weeks old.

A study in the journal Sleep analyzed the advice provided in 39 parenting books. Forty percent opposed co-sleeping; 28 percent endorsed it; 32 percent took no position.

Different patterns of co-sleeping were recommended in the books. Some promote co-sleeping only during the first weeks or months after birth; others recommend long-term co-sleeping in a “family bed.”

An American Academy of Pediatrics policy statement recommends infant room sharing. It advises parents that infants should sleep in the parents’ bedroom and close to their bed. The baby can be brought into the bed for feeding or comforting.

But an infant should be placed on a separate sleep surface when the parent is ready to return to sleep. The sleep surface should be firm. Soft objects and loose bedding should be kept out of the crib, cradle or bassinette.

Infants always should be placed to sleep on their back.