Is SIDS Caused By An Inner Ear Issue? Possibly

Though Sudden Infant Death Syndrome, also known as SIDS, has not yet been identified to have a specific cause, studies recently starting analyzing a possible connection between infant inner ear problems and SIDS. The research has left a lot of people wondering, is SIDS caused by an inner ear issue? I spoke with Dr. Daniel Rubens of Seattle Children's Hospital to learn more about SIDS, inner ear functionality, and how the two are connected.

In 2006, Dr. Susan Norton, a hearing expert at Seattle Children's Hospital, suggested to Dr.Rubens that he get in touch with Dr. Betty Vohr of Women and Infants Hospital in Providence, Rhode Island, with whom Norton had collaborated with on research in the past. Rubens approached Vohr and the state of Rhode Island at that time, to look at the newborn hearing tests of SIDS babies. "We never expected to find anything," says Rubens. In 2007, months into their research, Vohr called Rubens with a groundbreaking question. "Why did the SIDS babies have a hearing suppression in their right ear?"

The research was exciting, because it was new, and the numbers were statistically significant. In their research, 31 babies with a hearing suppression in their right ear succumbed to SIDS. The hearing tests that Rubens looked at with the Rhode Island Newborn Hearing Screening Program were hearing tests performed within 48 hours of birth and compared to babies that did not die of SIDS. The research was a potential game changer, because previously, studies on SIDS babies were not available before they passed. "The main way we've looked at SIDS babies is with an autopsy," says Rubens. Rubens compares looking at SIDS babies’ post-mortem to looking at a car crash. "You don't know if what you're looking at is part of the car crash, or what caused the car crash." That is to say, looking at an autopsy, it's difficult to say if findings are a cause of death, or a side effect of death.

In 2010, to explore the correlation between inner ear functionality and SIDS even further, Rubens and his research team began a new study, this time with mice. "We wanted to see if mice with a hearing suppression in their right ear had other problems," says Rubens. The team of researchers looked specifically at the arousal response (in this study, how well an animal can move or react when they experience a lack of oxygen and buildup of carbon dioxide during sleep). Rubens and his team of researchers found that mice that had a hearing suppression (whether in their right ear, left ear, or both ears) did not move away when faced with the lack of oxygen and buildup of carbon dioxide during sleep. Mice that had no hearing suppression would make vigorous movements in order to move their head away and access fresh air. In summary, a healthy animal would move away from the problem and survive and animals with inner ear dysfunction would remain in the original position and succumb to a fatal event.

While Rubens isn't suggesting that SIDS is only about the inner ear, he is suggesting that the inner ear problem does appear to put babies at a substantially higher risk. To put this in layman's terms, Rubens suggests looking at the possibility of SIDS on a ten point scale. In order for a baby to die from SIDS, they have to reach ten points. "The way I look at it is like this, when the baby is born, they have taken a hit which is very specific to these babies," says Rubens. "This gives them perhaps four points. It's not immediately fatal, but the four points represent damage to the inner ear, and potentially other areas of the brain. It's very specific." Now, Rubens adds in other possible contributing factors of SIDS. If the baby is exposed to smoking for example, this can add another three to four points. If the baby has a cold or is sleeping in a vulnerable position these could each add another two or three points. The initial four points specific to babies with inner ear problems is what puts them over the ten point mark. The specific problem is what pushes them over the edge."

The early 2008 hearing study, where hearing suppression was moderate but still statistically significant, created the basis for a larger scale comprehensive follow up hearing study. It took some years to organize this. Dr. Peter Fleming a renowned Pediatrician that has completed many large scale SIDS studies and his team, in collaboration with Rubens, have just started this study in June 2016 in the United Kingdom, "to really look at the hearing findings in detail." Though the study began only a few months ago, the team is hoping to have data in a year and a half to two years.

In addition, Marta Cohen, a pediatric pathologist, has begun looking at the inner ears of SIDS babies during autopsies — something that previously hasn't been done because it is not part of the standard autopsy. "It's slow going, because it's a delicate, difficult procedure to do," says Rubens. Cohen is also using CT and MRI imaging in her research. If consistent occurrences show up on these pictures, these imaging techniques could potentially be added to a newborn hearing test as an early indicator of SIDS risk soon after birth. Though it's too early in the research to provide any solid information, Rubens said that Cohen's findings appear hopeful.

Rubens describes the above studies as "important advances" to the research he's been working on for the past decade. "At this point in time, there is no test for SIDS," says Rubens. "We need to do a lot more research." Rubens goes on to tell me that it's not only funding that the research needs to continue, but the support from parents and people in the United States. "The way the hearing test in the United States is set at the moment, a newborn hearing test delivers only a pass/fail," says Rubens. The Rhode Island study looked at more information about newborn hearing capabilities, and provided Rubens and his team with important information. "We will have to change the way the data is kept for each State’s newborn hearing screening program," says Rubens. If families and parents tell their state that they want more detailed newborn hearing tests, and that they support it, the chances of continued research with more detailed findings increases.

"In England, we were able to do that," says Rubens. "It took years to create the relationships to get the study off the ground." But that doesn't mean the current study won't benefit the U.S. "Whatever we find in England will be useful for the United States," says Rubens. When the team gets results in England, they'll then be able to use it as a catalyst for further research in the United States and elsewhere. "We can come back to the United States and say, 'this is useful, because the US and UK use similar, if not the same equipment for the newborn hearing test'."

"Since this is relatively new research with some positive findings. it is controversial," says Rubens. "I'm fighting to get the support to keep it going." This is why testing isn't available yet. "We need to do more research," says Rubens. According to Rubens, a lot is hinging on the British hearing study. The team isn't just looking at newborn hearing, but at their medical records, at the mother's records, at whether or not the babies were subject to smoke, if they are put to sleep on their bellies, and more. Comparing this degree of detailed information between babies who died of SIDS and babies who did not die of SIDS will be very useful, and could help researchers understand much more about why babies die of SIDS, and how inner ear functionality contributes to it.

*A previous version of this article was published with inaccuracies about the scope of Dr. Rubens' research. They have since been corrected. For more information on the progress of Rubens' research, visit the SIDS Research Guild.