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.
Dr.Daniel Rubens
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.
MAKING PROGRESS
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.
While I think we can all agree that a test for SIDS would be amazing, we owe it to the patients and families we serve to be more skeptical of this research and the claim that OAEs can be used to test for SIDS.
There are a number of significant concerns with this research, but probably the biggest can be summarized by applying the criteria suggested by Rubens to a large group of newborns. Approximately 60% of newborns would match the criteria for OAE SNR in at least one ear reported for the SIDS group in that study. Flipping a coin actually yields higher sensitivity than using the OAE in the way suggested by Rubens.
There are a number of problems with this research, but this is certainly the most significant.
Ryan,
What you state is incorrect. The finding across the three tested frequencies reaches significance at P < .0001.
Our current plan is to complete a large-scale study from scratch and in far greater detail than the original study.
It is important to keep in mind that this is the first and only finding from when sids babies are alive from a universal currently utilized screening test.
In a nutshell we are saying that this deserves further research and we are planning to do that whatever we may find. The families deserve that. I'm more than happy to discuss further in person . Kind regards, Daniel Rubens
Dr. Rubens, I recall coming across some research indicating that children with unilateral hearing loss in the right ear tended to be more likely to fall behind a year academically than those who had hearing loss in the left ear. I think there was a theory that perhaps the right ear in a very young child would have otherwise utilized primarily the left hemisphere, whereas the left ear would favor the right hemisphere. Thus *perhaps* hearing loss in the right ear of an infant might result in an important function of the left hemisphere not being able to process the important high-frequency sounds. (The left hemisphere tends to be primed for language and other analytical functions.)
For what it’s worth, I grew up with bilateral hearing loss, but my hearing was much better in my right ear than in my left, so I was quite intrigued with that research.
Ryan, I agree. There is no reason that one ear should be more sensitive than the other in the case of oxygen deprivation. Sampling errors is a real phenomenon and spurious correlations abound. It is not surprising that this has not been funded, given the lack of face validity. Considering that nearly every baby receives a screening at birth, if failure on a hearing screening was an indicator of SIDS, it would be noticeable by now. However, as the investigator is convinced, perhaps another pilot study is in order? This is not a study that would actually require funding. Just some time and commitment.
Ryan and Virginia,
As a SIDS parent I wish more individuals who have time to critique the good and honest work of SIDS researchers would take the extra negative energy hanging out in the blogosphere and convert it towards positive solutions to find SIDS parents an answer.
Enough said until you have a walked a mile in our shoes. Hope in SIDS research is what keeps parents going who have suffered a tragic loss. We SIDS parents welcome the extra time you seem to have to contribute it in a more productive way to be a part of the solution and not part of juvenile and insensitive comments.
God bless Dr. Rubens and his team of researchers.
The sad reality is that there has been no significant progress in SIDS research over the past several decades. There are few researchers interested in it and even less funding. With such little research being done regarding SIDS it saddens me to see anyone discourage someone interested in it. After all when Dr. Donnall Thomas pursued bone marrow transplants they said it couldn’t be done. Progress is made with innovation and perseverance.
If more in-depth studies are done and in the end it shows no correlation, that is still progress. It is progress in the sense that it is one area that can be crossed off the long checklist of possibilities. One more area looked at, given consideration and researched. I think that as a medical professional one should not publicly reproach someone with curiosity and innovation. After all, the medical field would be no where without innovation, curiosity and people willing to think outside the box. I can imagine as an audiologist you would have an opinion regarding this study. But I think a more responsible way of making your opinions known would be to personally contact the researcher and share your input. What SIDS families want to see is progress….any progress. Even if it means by process of elimination.
Here’s a link to a CDC pdf compiling information from research about unilateral hearing loss and educational outcomes:
http://www.cdc.gov/ncbddd/hearingloss/documents/unilateral/dross-pkg06-unilateral-outcomes-table-cleared.pdf
Several studies showed that right-sided hearing loss was associated with poorer verbal skills and poorer academic functioning, while left-sided hearing loss was sometimes associated with reduced non-verbal skills. There are indications that even if a clear signal was reaching the unaffected ear, there could still be negative effects. Whatever caused the unilateral hearing loss may have also sometimes affected the development of the corresponding hemisphere.
An interesting finding !
Why just a right ear issue? Why not the left ear involvement, or unilaterally the left ear vestibular characteristics.
Spatial orientation is processed in the right brain, and not the left brain.
Jay Muhury.
It would be great if a simple hearing test could give us information about children with a potential SIDS risk. It is so sad to think of small infants dying for no reason and it makes you wish you could do something about it. It is interesting to think that the inner ear plays a role in our breathing as well. It makes you realize how little we actually know about the human body.