Research on Sudden Infant Death Syndrome (SIDS)

Last Editorial Review: 12/3/2004

SIDS is the term used to describe the sudden, unexplained death of a baby under one year of age. In the past, SIDS was sometimes called "crib death", even though cribs themselves do not cause SIDS. Researchers estimate that SIDS is the cause of about 2,500 infant deaths each year.

Like any loss of a child, SIDS can be devastating to a family. If you or your family has been touched by SIDS, you may want to seek counseling to help deal with the emotions of the loss. For more information on where to go for such counseling, please talk to your health care provider, or contact the First Candle SIDS Alliance at 1-800-221-7437.

Although the exact cause of SIDS is unknown, researchers have discovered trends in SIDS deaths that may help them understand this mysterious fatal problem. For instance:

  • SIDS is the leading cause of death in babies after one month of age.
  • Most SIDS deaths occur in babies less than six months old.
  • Babies placed to sleep on their backs are less likely to die from SIDS than those placed on their stomachs to sleep.
  • Babies are more likely to die from SIDS when they are placed on or covered by soft bedding.
  • African American babies are twice as likely to die from SIDS as white babies.
  • American Indian babies are nearly three times more likely to die of SIDS than white babies.

Ways to Reduce the Risk of SIDS

Even though the exact cause of SIDS is unknown, researchers have identified steps that caregivers can take to reduce the risk of SIDS, including:

  • Always place your baby on his or her back to sleep, for naptime and bedtime.
  • Make sure your baby has a safe sleeping environment, which includes:
  1. Placing the baby on a firm mattress, such as in a safety-approved crib. Research has shown that placing a baby to sleep on soft mattresses, sofas, sofa cushions, water beds, sheepskins, or other soft surfaces can increase the risk of SIDS; and
  2. Removing soft, fluffy bedding and stuffed toys from the baby's sleep area. Make sure you keep all pillows, quilts, stuffed toys, and other soft items away from your baby's sleep area.
  • Make sure the baby's head and face stay uncovered during sleep. Keep blankets and other coverings away from your baby's mouth and nose. Dressing the baby in sleep clothing will avoid having to use any covering over the baby. If you do use a blanket or another covering, make sure that the baby's feet are at the bottom of the crib, the blanket is no higher than the baby's chest, and the blanket is tucked in around the bottom of the crib mattress.
  • Don't allow your baby to get too warm during sleep. Your baby's room should be at a temperature that is comfortable for an adult. Too many layers of clothing or blankets can overheat your baby.
  • Don't allow smoking around your baby.
  • Make sure all of your family members, baby-sitters, and anyone else who cares for your child knows to put the baby on his or her back to sleep, and other ways to reduce the risk of SIDS.
The Institute's publications, Babies Sleep Safest on Their Backs and Necesito Dormir Boca Arriba: Reduza el riesgo del sindrome de muerte subita del bebe (Spanish), provide more information on reducing the risk of SIDS. You can also review a complete listing of the Institute's materials about SIDS.

The Back to Sleep Campaign

Reducing SIDS deaths has been a goal of the NICHD since it was founded. In 1974, congress passed the Sudden Infant Death Syndrome Act (Public Law 93-270), which placed the NICHD at the forefront of SIDS research. This Act also charged the NICHD with providing information to the people of the United States about SIDS and ways to reduce the risk of SIDS.

In 1991, as a result of NICHD-supported research, the American Academy of Pediatrics (AAP) began recommending that babies be placed on their backs to sleep, at nap time and at bedtime, to help reduce the risk of SIDS. In 1994, the NICHD joined the AAP and other partners in starting the Back to Sleep campaign, an effort to educate the public about reducing the risk of SIDS by placing babies to sleep on their backs. Since that time, the number of SIDS deaths has dropped by 50 percent.

The Back to Sleep campaign, now nearly a decade old, has expanded its messages to address the topics of SIDS and SIDS reduction among certain ethnic groups. This expanded effort now includes the Back to Sleep African American outreach, Back to Sleep materials in Spanish, and a forthcoming outreach project in American Indian communities. By partnering with national and community-based organizations that serve these audiences, the Back to Sleep campaign can get the safe sleeping message to many communities, to save infant lives.

The Institute maintains a Web site for the Back to Sleep campaign, which outlines the history of the campaign and of SIDS in the United States, provides general information about SIDS and ways to reduce the risk of SIDS, and offers free materials for learning more about SIDS risk reduction. You can also call 1-800-505-CRIB (1-800-505-2742) to order free Back to Sleep materials.

NICHD Research on SIDS

The NICHD has been working to reduce the number of SIDS deaths, both through the Back to Sleep campaign, and through research into the causes and features of SIDS.

Recent research suggests that many SIDS babies are born with brain defects that may increase their risk of SIDS. Studies of SIDS victims show that many SIDS infants have an abnormality in a network of neurons in the brainstem that are involved in the developing and controlling blood pressure and breathing, temperature regulation, and sleep and waking. Although this brain defect may not be the sole cause for SIDS, researchers have some ideas about how the brain problem may be involved in SIDS:

  • Research suggests that stomach sleeping and soft bedding increase an infant's risk of re-breathing his or her own exhaled air. When an infant is sleeping in its stomach, the exhaled air (carbon dioxide) may get trapped between the infant's face and the bedding. When the infant breathes exhaled air, the oxygen level in the baby's body drops and the carbon dioxide level rises, which may lead to SIDS. If a baby is re-breathing exhaled air and not getting enough oxygen, the brain usually triggers the baby to wake up and cry. This action changes the baby's breathing and heart rate, making up for the lack of oxygen. But, a baby with a flaw in the brainstem might lack this method of protection and may be at greater risk for SIDS.
  • Another theory is that stomach sleeping and/or soft bedding, such as quilts and comforters, increases the risk of overheating. If the baby's face or head is covered by bedding, the baby will begin to overheat. The brain usually triggers the baby to wake-up and move and free his or her head. A baby with a flawed brainstem however, might lack this method of protection and may be at greater risk for SIDS.
  • Babies born with defects in other parts of their brains or bodies may also be at greater risk for SIDS. These defects might be the result of prenatal exposure to a toxic substance. For example, smoking during pregnancy can reduce the amount of oxygen the growing baby receives, making it more susceptible to conditions of low oxygen later in life.


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A recent study also found a greater risk of SIDS among babies who were regularly placed on their backs to sleep, but were switched to the less-familiar stomach sleeping position.

Other research, funded by the NICHD, helped to identify risks for SIDS among Native American communities. The findings of this study have been vital in shaping the campaign's outreach project for American Indian communities, in hopes of finding ways to reduce the risk of SIDS.

Source: National Institutes of Health (

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