Infant Hearing Test Results
A recent study found that babies in a Rhode Island study group who died of Sudden Infant Death Syndrome (SIDS) universally shared the same distinctive difference in their newborn hearing test results for the right inner ear, when compared to infants who did not have SIDS (Early Human Development, July 2007).
This is the first time doctors might be able to identify newborns at risk for SIDS by a simple, affordable and routine hearing test administered shortly after birth. In the study, led by Daniel D. Rubens, MD, of Children's Hospital and Regional Medical Center in Seattle, medical records and hearing tests of 31 babies who died from SIDS in Rhode Island were examined and compared to healthy babies.
The cause of SIDS, also known as "crib death" and "cot death," has eluded physicians and researchers. Responsible for many previously unexplainable deaths of infants usually two to four months old and striking boys more than girls, SIDS causes the deaths of approximately 1 in 1,000 newborns worldwide, making it the largest cause of death in young infants.
In the United States, approximately 3,600 deaths each year were attributed to SIDS from 1992-1999 (Archives of Pediatric and Adolescent Medicine, April 2004). Death occurs during sleep, seemingly with no warning and no previous symptoms.
Various causes have been suggested, including disturbances in respiratory control and infant overheating, but to date nothing has proven conclusive.
It is known that the inner ear contains tiny hairs that are involved in both hearing and vestibular function. Dr. Rubens suggests that vestibular hair cells are important in transmitting information to the brain regarding carbon dioxide levels in the blood and suspects that injury to these cells will disrupt respiratory control, playing a critical role in predisposing infants to SIDS.
The SIDS infants in Dr. Rubens' study showed a consistent four point lower score in their standard newborn hearing tests, across three different sound frequencies in the right ear, when compared to babies that didn't die from SIDS. Additionally, healthy infants typically test stronger in the right ear than the left. However, in each of the SIDS cases studied, the right ear tested lower than the left, reversing the test results of healthy babies.
"This discovery opens a whole new line of inquiry into SIDS research," Dr. Rubens said. "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."
He urges further research, adding "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."
