It remains one of the great medical mysteries, and one that haunts many new parents: A baby goes to sleep — and never wakes up after suffering sudden infant death syndrome.
It happened last summer to 5-month-old Suzanna Lewis of Vancouver, Wash. Her mother, Marchand Lewis, vividly recalls that morning.
"Picking your child up out of a crib who's passed away," Lewis told ABC News. "I mean, she was lifeless, and heavy and limp. So, I absolutely knew as soon as I grabbed her that she had gone."
Even when parents follow all the guidelines to avoid such a tragedy — when babies are put to bed on their backs, as Suzanna was, and blankets removed from their cribs — infants still die without warning.
SIDS kills about 2,500 babies in the United States each year. They usually die in their beds, with no warning, no previous symptoms and no known cause.
Now, researchers at Seattle's Children's Hospital may have found a valuable clue to SIDS, one that might predict which infants are most at risk.
Dr. Daniel Rubens, an anesthesiologist at Seattle Children's Hospital, and lead investigator in the study, which appeared in the journal Early Human Development, said, "I had a hunch. And then you look in the inner ear and you know, 'yes, look, there's something here.'"
Rubens studied the medical records of 31 SIDS babies, including results from hearing tests given to almost every newborn before they leave the hospital.
Rubens found that all the SIDS babies had weaker hearing in their right ears than their left. And the difference was exactly the same: four points lower, across three different frequencies — findings that are statistically significant.
But what is there about an infant's inner ear that might lead to SIDS? While critical for hearing and balance, there are suggestions that cells in the inner ear may also be involved in the control of a baby's breathing and blood pressure.
Dr. Gerald Laughlin, chief of pediatrics at New York Presbyterian/Weill Cornell Medical Center, says much more research needs to be conducted before we understand what's actually going on and how we might use this information.
"This is an interesting observation," he told ABC News. "But it's way too early for parents to be focusing on these subtle hearing differences. There have been lots of suggested markers for SIDS that, when studied more closely, never panned out."
Rubens, the lead author of the study, agreed. These findings represent a new hope, he said, a possible way to eventually identify babies at risk for SIDS.
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