By David H. Kirkwood
SEATTLE—Imagine that when a newborn infant is screened for hearing loss, as is done routinely in every U.S. state and in many other countries, the same test could also determine if the baby is at risk for sudden infant death syndrome (SIDS), the mysterious condition that kills some 4000 seemingly healthy infants a year in the U.S. while they are sleeping.
It sounds unlikely, yet there is compelling scientific evidence that a hearing abnormality that is detectable by newborn hearing screening is a warning sign of SIDS. Moreover, there is a determined scientist-physician, Daniel D. Rubens, MD, who has made it his mission to ensure that additional research is conducted that may make it possible to identify newborns who are vulnerable to SIDS.
That alone would allow a SIDS-prone infant’s parents and medical providers to take steps to protect the child during the period, usually the first six months of life, when nearly all SIDS deaths occur. Better yet, research might discover a way to correct the underlying condition that makes the child vulnerable.
Rubens, a 52-year-old anesthesiologist, is an associate professor and transplant director for anesthesia at Seattle Children’s Hospital. Born in England, he earned his medical degree at the University of New South Wales in Australia, and began practicing medicine at Seattle Children’s in 1999.
His battle against SIDS began in 2002, when he read an article about SIDS. “I was drawn to the mystery about it,” he told a Seattle Times reporter. Despite being a busy clinician, he decided to start researching the condition, which inflicts so much tragedy on families.
RHODE ISLAND STUDY
The findings that first pointed to a link between abnormalities in the inner ears of newborns and SIDS were published by Rubens and colleagues in a 2007 study in Early Human Development.
Although it is not known what causes SIDS, it has long been believed that a disturbance in respiratory control plays a prominent role. It has also been shown that the vestibular apparatus in the inner ear plays an important role in respiratory control during sleep.
Therefore, Rubens and his co-researchers–Betty R. Vohr, Richard Tucker, Courtney A. O’Neil, and Winnie Chung–decided to analyze data from the Rhode Island Department of Health Infant Mortality Database for 31 babies born between 1993 and 2005 who had undergone newborn hearing screening and then died of SIDS.
As Rubens et al. explained in their article, “We hypothesized that an inner ear insult resulting in disruption of vestibular function might play a critical role in the predisposition for SIDS.”
For their study, the researchers compared the data from the 31 SIDS victims with data from 31 controls who were individually matched with the SIDS babies by gender, term versus pre-term age, and NICU versus well baby nursery.
The evidence they discovered could hardly have been more convincing. All 31 of those infants who had died of SIDS had been found, during newborn hearing screening using TEOAE (transient evoked otoacoustic emissions) testing, to have significantly decreased signal-to-noise ratios at 2000, 3000, and 4000 Hz (p < 0.05) on the right side compared to the controls.
Meanwhile, newborn screening had not found a similar right-side hearing loss in any of the 31 controls.
Prior to their study, the authors wrote, newborns at risk for SIDS “are indistinguishable from other newborns and are only identified following a later fatal event.”
However, as a result of the Rhode Island study, they concluded, “A unilateral difference in cochlear function is a unique finding that may offer the opportunity to identify infants at risk of SIDS during the early postnatal period with a simple non-invasive hearing screen test. The ability to implement preventative measures well in advance of a potential critical incident would be an important breakthrough.”
NO BREAKTHROUGH YET
The article received a lot of attention, and Rubens and his colleagues hoped that it would lead to more research being conducted along similar lines. In an interview, Rubens said that several states discussed doing their own studies, but for various reasons nothing came of it. One major obstacle is the shortage of funding for research compared to the large number of research proposals.
However, Rubens was not discouraged. He helped establish the SIDS Research Guild at Seattle Children’s to raise money for research and to publicize what is being done.
The home page of the guild’s web site states, “We believe that the solution to SIDS is finally within reach. It is our sincere hope that our work is a bold step to solving a lifelong medical mystery once and for all and giving back to the world infants that die before their time.”
Along with asking for donations on its web site, the guild held its first fundraising event earlier this year, which brought in about $20,000.
Rubens has also continued his research. In a 2013 article in Neuroscience, Travis Allen, AJ Garcia III, Jing Tang, Jan-Marino Ramirez, and he reported on the findings of a study using wild mice. They injected drugs in some of the mice to induce inner ear hair cell dysfunction. They found that, unlike the controls that were not injected, when the injected animals were exposed to a suffocating mixture of gases, their arousal movements in response were suppressed.
These findings, the authors say, “indicate that the inner ear appears to play an integral function in the ability to arouse and physically escape from suffocating gas mixtures.”
That is consistent with Rubens’s theory that the reduced hearing levels among the Rhode Island newborns who later died of SIDS were symptomatic of damaged vestibular cells in the right ear. Along with maintaining balance, vestibular cells play a role in transmitting information that regulates a baby’s breathing and arouses a baby who is exposed to a suffocating environment. If those vestibular cells are not functioning properly, they will not arouse a sleeping baby who has moved into a position where breathing is restricted. As a result, the child may suffocate.
Looking ahead, Rubens sounded optimistic, though he emphasized that more research would be needed before there is a hearing test for SIDS. He reported that scientists in the United Kingdom are planning to conduct a study similar to the one in Rhode Island, only much larger. It is expected to involve 100 or more cases of SIDS and 300 controls.
If the British study confirms the earlier one, Rubens said that he and his colleagues would be requesting large-scale institutional funding. One goal is to devise a risk scoring system for SIDS that would combine a hearing screening exam with a comprehensive risk factor assessment at birth.
Another objective is to develop techniques to detect a pending fatal SIDS-like event in time to institute effective resuscitation strategies.
In addition, the research with animals is focused on finding methods to detect and prevent a lethal event well ahead of time.