Light Shed on Mystery of Sudden Infant Death Syndrome (SIDS)

< Aug. 01, 2007 > -- A simple, affordable, and routine hearing test given to an infant soon after birth may identify babies at risk for sudden infant death syndrome (SIDS), a new US study finds.

SIDS kills about one in 1,000 infants worldwide. Death occurs while the infant is sleeping and does not appear to have any obvious warnings or prior symptoms.

Most of the victims are between two to four months old. Boys are more likely than girls to die of SIDS. Many causes have been suggested for SIDS, but to date no single research study has been conclusive.

SIDS is the major cause of death in babies from one month to one year of age, occurring most often between two and three months of age. The death is sudden and unpredictable; in most cases, the baby seems healthy. Death occurs quickly.

SIDS Infants Studied

Dr. Daniel D. Rubens and colleagues at the Children's Hospital and Regional Medical Center in Seattle studied the medical records and hearing tests on 31 Rhode Island babies who died of SIDS and compared them to healthy babies.

They found that all the infants shared the same distinctive difference in newborn hearing test results for the right inner ear.

Compared with other babies, those who died of SIDS scored four points lower in standard newborn hearing tests, across three different sound frequencies in the right ear.

However, the infants who died of SIDS had lower scores for the right ear than the left. The study was published in the journal Early Human Development.

Exciting Research Possibilities

"This discovery opens a whole new line of inquiry into SIDS research," Dr. Rubens says. "For the first time, it's now possible that with a simple, standard hearing test, babies could be identified as at risk for SIDS, allowing preventative measures to be implemented in advance of a tragic event."

The inner ear contains tiny hairs involved with both hearing and vestibular (balance) function. Vestibular hair cells may play an important role in transmitting information to the brain about levels of carbon dioxide in the blood, Dr. Rubens suggests. Injury to vestibular hair cells may disrupt respiratory control and predispose infants to SIDS.

Dr. Rubens urges further research in this area. "We must now fully explore all aspects of inner ear function and SIDS and analyze testing frequencies higher than those currently tested by newborn hearing screen centers," he says.

Cause of SIDS Remains Elusive

This research is important because the cause of SIDS, also known around the world as crib death and cot death, has remained inexplicable to physicians and grieving parents for centuries. SIDS is the largest cause of death in young infants worldwide. Changes in infant care have been promoted, including the Back to Sleep program discouraging sleeping on the stomach, and avoiding exposure to cigarette smoke. Always consult your child's physician for more information.

What can be done to decrease the risk of SIDS?

There currently is no way of predicting which babies will die from SIDS. However, there are a few measures parents can take to lower the risk of their baby dying from SIDS, including the following:

• prenatal care
  Early and regular prenatal care can help reduce the risk of SIDS. Proper nutrition, no smoking or drug or alcohol use by the mother, and frequent medical check-ups beginning early in pregnancy might help prevent a baby from developing an abnormality that could put him/her at risk for sudden death. These measures may also reduce the chance of having a premature or low birthweight baby, which also increases the risk for SIDS. The risk of SIDS is higher for babies whose mothers smoked during pregnancy.

• put your baby on his/her back for sleep, even at naptime
  Parents and other caregivers should put babies to sleep on their backs as opposed to on their stomachs. Studies have shown that placing babies on their backs to sleep has reduced the number of SIDS cases by as much as a half in countries where babies had traditionally slept on their stomachs. The back sleep position is the best position for babies from 1 month to 1 year for sleep, including naps.

• proper bedding
  Make sure that your baby sleeps on a firm mattress or other firm surface. When your baby is very young, do not place soft stuffed toys or pillows in the crib with him/her. Some babies have smothered with these soft materials in the crib.

• temperature control
  Babies should be kept warm, but they should not be allowed to get too warm. An overheated baby is more likely to go into a deep sleep from which it is difficult to arouse.  Keep the temperature in your baby's room so that it feels comfortable to you.

• pediatric healthcare
  If your baby seems sick, call your physician right away. Parents should take their babies for regular well baby check-ups and routine immunizations. Claims that immunizations increase the risk of SIDS are not supported by research. If a baby ever has an incident where he/she stops breathing and turns blue or limp, the baby should be medically evaluated for the cause of such an incident.

Always consult your child's physician for more information.