A Clinical Research Summit - Part One

By Mark Ross, Ph.D

Editor: Where is the hearing health care industry headed? What will be the major issues facing it in five years? How can we fix the issues facing it now? A recent conference convened by the Starkey Hearing Research Center addressed these issues, and the conclusions were presented in the June 2007 edition of Hearing Review. In this article Dr. Ross addresses those conclusions.

This article first appeared in "Hearing Loss" magazine, and is republished with Dr. Ross' kind permission.

This is part one of three parts.

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Part One

Part Two

Part Three

For practitioners in any field, "state-of-the-art" conferences serve as a kind of platform from which the current status of a profession can be examined in order to more effectively chart a path for the future. We must, in other words, know where we are so that we can better plan where we want to go. In the Hearing Care Industry, the most recent such conference was convened by the Starkey Hearing Research Center early in 2007. However, the approach used seemed a bit more creative than that employed in the usual such conference. Rather than simply being assigned a topic, a select group of participants was asked to jointly identify the top challenges and issues that would be facing the field in the next five years.

The six topics that emerged during the two-day summit represented those with which the participants - all leading figures in the field - had personally wrestled. Although the report of the conference, which appeared in the June 2007 edition of Hearing Review, is divided into six chapters authored by different individuals, the sentiments expressed in each one represent a consensus of the entire group. Their relative importance is not reflected in the order in which they are discussed below. But it is important to note that all of them relate, directly or indirectly, to the ultimate goal of enhancing the communication capacities of people with hearing loss.

Using Clinical Measures to Predict Real-World Performance

The first challenge deals with the frequently-observed disparity between the technical performance of a hearing aid in a clinic, and the "real-world" performance of that same hearing aid. Right now, a person's test scores in a clinic are an imperfect predictor of how the person will function with the aid in his or her usual environment. This is not a trivial consideration. Consider someone who is tested with and purchases a "premium" hearing aid at a premium price. These aids include a number of advanced features not found in a "basic" digital hearing aid. The test scores and technological possibilities of the aid's special features can't help but raise a user's expectations regarding its performance outside of the clinic. Sometimes these heightened expectations are fulfilled, but sometimes not. The goal is to develop clinical measures that can predict, with a reasonable degree of certainty, performance of the hearing aid in a user's' normal environment. People shouldn't be investing a lot of money in "top-of -the-line" technology without some reasonable assurance that the added cost will be reflected in noticeable listening benefit.

It's evident why there is often a disparity between the way a hearing aid functions in a clinic and in one's usual environment: Listening conditions generated in a clinical test situation differ significantly from those that occur elsewhere. In the "real world," a person is exposed to a host of various and often unique conversational partners and acoustical environments. Interactions may occur between certain hearing aid features and various environmental listening conditions. Therefore, superior performance of a specific hearing aid or feature observed in the clinic may not apply elsewhere.

The challenge we face is in finding ways to rectify this discrepancy, as it always seems easier to define a problem than to develop a research strategy to address it. Conference participants made numerous recommendations for developing such a strategy, foremost among these being the replication of natural listening conditions in a clinic, perhaps by better defining the actual type of noise environment that a particular person encounters. One way this can be accomplished is by incorporating data logging capabilities into a hearing aid, which is already done on a limited basis with some aids. This would permit clinicians to better understand the listening problems faced by a specific person. Additionally, advances in virtual-reality technology may permit people to interact with computer-simulated environments that are similar to what would be occurring outside of a clinic. In the meantime, however, I would strongly suggest that new hearing aid users be sure to do their own careful analyses and comparisons during the trial period.

Understand Individual Audiometric Differences

The second challenge reviewed at the conference concerned the fact that people with similar audiograms will not necessarily understand speech similarly. While numerous conditions can produce comparable audiograms, the underlying pathology may be dissimilar and affect different parts of the auditory system. Consequently, the resulting behavioral consequences would tend to vary. Research studies have demonstrated that differences in speech comprehension may still persist even when people with similar audiograms are aided identically with hearing aids.

A cochlea can be damaged or stressed by any number of factors, including noise trauma, ototoxic drugs that may affect inner as well as outer hair cells, and various genetic abnormalities among many others. Each of these different conditions can produce varying behavioral consequences. The variability in speech comprehension is usually greater when hearing-impaired people are tested under noisy conditions than in quiet. Even the type of noise may increase the differences in speech comprehension observed among people with similar audiograms. For example, interrupted noise will often have a greater effect upon some people than steady or constant noise. The point is that audibility alone - i.e., the portion of the speech signal that can be perceived - is not a perfect indicator of how well someone can understand speech. Other factors come into play, such as differences in temporal (time) and spectral (frequency) resolution abilities and whether or not there are any regions of dead hair cells in the cochlea. One of the recommendations made at the conference was for the development of additional clinical tests, presumably simpler ones than those now available, which can be used to identify these factors.

The summary questions asked by the conferees focused on whether hearing aid fittings could be significantly improved if more was known about each person's unique auditory abilities. Would alternative fitting strategies or algorithms be appropriate? Perhaps more detailed psychoacoustic information would demonstrate the necessity for developing some new hearing aid features. I think consumers will agree that these are key questions and appropriate topics for future research. But even if additional information about a person's auditory skills cannot presently result in improved hearing aid fittings, such knowledge can be extremely valuable in helping someone develop realistic expectations. Sometimes it helps to know what is not possible as well as what is.

Part One

Part Two