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Ears May Hold Answers to the Mysteries of Sudden Infant Death Syndrome

An unexplained medical phenomena that has eluded doctors and scientists to this day is why millions of apparently healthy and thriving infants around the world die in their sleep. While Sudden Infant Death Syndrome (SIDS), also known as cot death, remains a mystery, new groundbreaking research may hold the answer to why some babies succumb to this condition, and pinpoint its underlying causes.

The key to this tragedy, according to researchers at the Childrens Hospital and Regional Medical Center in Seattle, may lie in the complex process that starts at birth, and can trigger an unfortunate chain of events, which sometimes culminate in the infants death. However, the Seattle researchers claim that a simple postnatal ear test can detect anomalies that predispose some babies to SIDS, and potentially save their lives.

A Tragedy Shrouded in Mystery

In the United States alone, an estimated 3,600 apparently healthy babies die each year in their sleep without any prior warning signs. Worldwide that figure is 1 in 1,000 newborns. For years researchers around the world focused on a wide range of potential causes, including respiratory disturbances, heart problems, various infections, exposure to cigarette smoke, and overheating. None of these suspected triggers was ever irrefutably proven to cause SIDS. Neither did vaccines, as suggested in the 1980s by an Australian researcher who claimed there was a link between the standard childhood immunizations and cot death. Those claims were debunked by follow-up studies, including ones carried out by the Centers for Disease Control and Prevention and the American Academy of Pediatrics.

In the early 1990s the health authorities, baffled by the lack of detectable causes of SIDS, suggested that newborns should sleep on their backs rather than on their stomachs to allow easier breathing. While the death rate has, indeed, plummeted considerably since the Back to Sleep campaign was launched, conclusive triggers still have not been established. SIDS remains the leading cause of death among healthy infants between one and four months of age.

Clues Point to Ears

The Seattle study, which was published in the July 2007 edition of Early Human Development, suggests that not one single anomaly causes SIDS, but, rather, multiple interacting factors, which snap into action minutes before birth. As mothers push to deliver the baby, an intricate series of events happens to the childs body: the blood rushes through the umbilical cord into his heart and brain. Eventually the onslaught of blood from the heart reaches the tiny vessels inside the ear which, in some cases, are not able to handle the pressure and end up rupturing, damaging the inner hair cells. Since these microscopic hair cells are pivotal in transmitting information to the brain about the bloods carbon dioxide levels -- dangerous when inhaled in high concentrations -- injury to these vital cells disrupts the breathing control and can trigger death.

Dr. Daniel Rubens, an anesthesiologist at the Seattle Childrens Hospital and Regional Medical Center, who headed the study, examined medical records of 31 SIDS victims who died in Rhode Island a state with a particularly reliable database of newborn hearing screening and infant deaths -- and compared his findings with the control group of healthy babies. The SIDS infants showed a consistent four-point lower score across three different sound frequencies in the right ear as compared to infants who didnt die from SIDS. Also, right ears in healthy babies are normally stronger than the left, but in SIDS cases, Dr. Rubens reported, the right ears were weaker, which may mean the trauma of delivery injured the inner ears and made the infants more prone to cot death.

While more research is needed to understand all the complexities of SIDS, Dr. Rubens says, it is possible that a simple, standard hearing test can identify babies at risk, allowing preventative measures to be implemented.

Risk reduction measures, according to the National Institute of Child Health and Human Development, include on-the-back sleeping position on a firm mattress covered with a fitted sheet; dressing the baby in light sleep clothing; and keeping the room well ventilated, at a temperature that is comfortable for an adult.

What The Future Holds

Since newborn hearing tests can detect at-risk infants, consistent testing is a crucial first step, Dr. Rubens says. The good news is that the U.S. has made great progress in screening newborns - 95 percent are currently tested, up from only 3 percent in 1989. According to National Institutes of Health, 39 states plus the District of Columbia and Puerto Rico have mandatory newborn screening, and additional five states have voluntary programs.

Does that mean we can now tell parents that we have the answer to preventing SIDS? We are not at that point yet, and further studies to explore all the aspects of inner ear functions have to be done, Dr. Rubens says. However, what is promising is that this study opens up a whole new area of inquiry into SIDS.

A follow up study is being planned, Dr. Rubens says, opening up great possibilities, and, hopefully leading to a new understanding of this syndrome.

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