Summary

Hearing loss is the most common sensory disorder in the United States, and the prevalence and severity of hearing loss—and hearing difficulties—increase with age. While approximately one in five Americans experience hearing loss, most individuals with hearing loss (about 83 percent) are over the age of 50. The term hearing loss is generally used to reflect a diagnosis based on a clinical measurement of hearing ability, often using the pure-tone audiogram.¹ The term hearing difficulties, on the other hand, is more strongly associated with hearing trouble perceived by the individual and may or may not be reported by adults with measured hearing loss. Hearing difficulties may also be perceived by adults without measurable hearing loss. The value of interventions for hearing difficulties in adults depends, in part, on what aspects of an individual’s lived experience matter the most to that person. Evaluations of the effectiveness of interventions that do not consider these important lived experiences may not accurately capture individuals’ perceptions of their functional abilities or the effect their hearing difficulties have on their quality of life.

While diagnostic tests are used to determine the cause of signs and symptoms, outcome measures are used to evaluate an intervention’s effect. When assessing the effect of an intervention, researchers and clinicians can consider a multitude of outcomes to measure. A core outcome set

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¹ In this report, the committee favors the use of the term adult with hearing difficulties, which is more focused on perceived troubles with hearing. However, the term hearing loss is used when referring specifically to a measured impairment, diagnosis, or when citing an original source.

recommends the specific outcomes (i.e., areas of hearing, communication, and beyond) that should be measured and reported, at a minimum. The use of a core outcome set—and of specific corresponding measures (i.e., the tools or instruments used to assess those core outcomes)—can enhance the consistency and quality of research, facilitate the comparison of different interventions, support clinical decision making, and focus on the outcomes that matter the most to adults with hearing difficulties. However, although several groups have created core outcome sets for specific hearing loss etiologies or interventions, no core outcome set has been broadly accepted by the hearing health community.

STATEMENT OF TASK AND STUDY FOCUS

With support from a coalition of sponsors, the National Academies of Sciences, Engineering, and Medicine (the National Academies) formed the Committee on Meaningful Outcome Measures in Adult Hearing Health Care in late 2023. The committee comprised 13 members with a broad range of expertise, including hearing health care, etiology of and interventions for hearing loss (and hearing difficulties), outcome measurement, primary care, disability and rehabilitation, quality of life, health disparities, public health, and epidemiology. The sponsors charged the committee with examining the state of the science in outcomes research for hearing health interventions in adults and to recommend the outcomes (the core outcome set) and corresponding outcome measures that should be used across interventions and settings at this time, with an emphasis on the outcomes that are most meaningful to adults with hearing difficulties and the clinicians who treat them.² The committee also was charged with making recommendations on areas of needed research on meaningful outcome domains (including hearing, communication, and domains beyond hearing and communication)³ and on the approaches needed to guide the development and refinement of standardized measures.

This report focuses on meaningful outcomes and the measures used to evaluate the efficacy and effectiveness of interventions rather than focusing on the types of assessments used to diagnose hearing loss or determine candidacy for various devices. While the committee contends that outcome measurement is an important part of clinical practice and research, this study does not focus on whether outcome measurement should be done. Rather, the committee starts with the assumption that outcome measurement is being performed and provides recommendations for the outcomes

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² The complete statement of task is presented in Chapter 1 of this report.

³ A health outcome reflects a change in health attributable to an intervention. Several related outcomes may be grouped into a category called an outcome domain.

that are most meaningful to measure and the measures that are most appropriate to use in order to create more consistency in outcome measurement for hearing health interventions.

BACKGROUND

The most common causes of hearing loss are age; exposures to noise, ototoxic drugs or chemicals; and genetics. Age-related hearing loss begins in early adulthood and progresses gradually. A range of risk factors exacerbate age-related hearing loss, including gender, ethnicity, environment, lifestyle, health comorbidities, and genetics. Some common characteristics of age-related and noise-induced hearing loss are progressive bilateral hearing loss, an inability to hear sounds at high frequencies, and challenges understanding speech, particularly in complex listening situations such as with background noise. Several approaches to treating hearing loss exist, and the choice of intervention may depend upon the etiology of the individual’s hearing loss and their goals. However, hearing aids have been the most common treatment for several decades.

COMMITTEE PROCESS

The committee followed several general best practices that have been identified for developing core outcome sets, including specifying a clear scope, involving key partners, and using a consensus process.

For this study, the scope was largely specified by the statement of task, although with refinement from the committee. The committee considered a wide range of etiologies but primarily focused on acquired adult-onset hearing loss (and hearing difficulties), which is most often caused by aging, noise exposure, or both. While the committee considered all adults (age 18 and older), it focused primarily on older age groups. The committee considered its scope to include a wide range of interventions, including devices, rehabilitation and training strategies, and pharmaceuticals and biological therapies; per the statement of task, the committee did not consider surgically placed prosthetic devices. The committee approached its work broadly to be able to apply its recommendations to both current and emerging individual-level interventions as well as to a range of settings and purposes. The committee focused on outcomes related directly to the effectiveness of the intervention itself and excluded the assessment of outcomes that could be highly influenced by systems or practice patterns, such as cost-effectiveness or patient satisfaction. The accessibility and affordability of hearing health care, which were examined in the 2016 National Academies report Hearing Health Care for Adults, were beyond this committee’s scope of work.

In any National Academies consensus study it is standard practice to include key partners and use a consensus process, although the particular approach to consensus will vary from study to study. The committee’s review of best practices for core outcome set development found that there is currently wide variation in the specifics of how consensus is reached on the components of a core outcome set. In many cases a Delphi-type voting process is used, with multiple parties and multiple rounds of balloting determining the final core outcome set. This committee chose, by contrast, to rely on an evidence-based review and synthesis of the literature to identify a set of core outcomes as well as the best measures to assess those outcomes. While the committee recognizes that there may be some isolated situations where its recommendations will not apply, it sought to develop recommendations that would be as broadly applicable as possible. The committee further recognizes that the measurement of additional outcomes will likely be warranted in many contexts.

Figure S-1 provides an overview of the committee’s overall process for determining a core outcome set and corresponding measures. While assembling an initial list of outcomes to consider for the core set, the committee simultaneously examined the hearing health outcome literature to begin an inventory of existing outcome measures for each of the candidate core outcomes.

Core Outcome Set

The committee’s first step in determining a core outcome set was to consider an extensive list of potential outcome domains and individual outcomes based on literature reviews of outcomes typically reported in studies of hearing interventions. The committee also hosted public webinars to hear directly from adults with hearing difficulties as well as clinicians and professional groups, and the committee established an online platform to invite comments from members of the public. Working with the information gathered from these sources, the committee conducted multiple iterative discussions of the evidence identified to create a comprehensive and clearly defined set of outcomes to be considered for a core outcome set.

As shown in Figure S-2, the committee considered both proximal and distal outcomes. Proximal outcomes are evaluated at the time of intervention (i.e., verification that the intervention was applied successfully). Distal outcomes are the outcomes that are typically most meaningful to adults with hearing difficulties.

Next, the committee conducted a more in-depth exploration into which outcomes are the most meaningful to adults with hearing difficulties and their clinicians. In general, the meaningfulness of an outcome reflects the perceived importance of that outcome by adults with hearing difficulties and by clinicians.

Recognizing that any single outcome will be meaningful to some individuals or populations, and may depend on context, the committee sought to determine which outcomes are meaningful across populations. Given the limited direct evidence regarding the most meaningful outcomes, the committee also considered evidence of the prevalence and severity of hearing-related complaints among those with hearing difficulties. A related concept, importance to measure, reflects whether an intervention can directly affect the outcome or whether measurement of the outcome provides information that would be helpful for clinical decision making.⁴ Since the committee was charged with recommending a core outcome set that applies across settings, interventions, a range of severities, and multiple etiologies of hearing loss, the committee concluded that any outcome in the core outcome set needs to be universally meaningful and important to measure across all contexts. The broadness of the scope of applications of the core outcome set also means that it needs to be feasible to measure in all contexts.

Therefore, after amassing a list of outcomes to consider, the committee used three main criteria to narrow down the outcomes to be considered for the core set (see Figure S-1). First, the committee required that the outcome be consistently defined across the literature and have a strong, established association with hearing difficulties. Second, the committee asked that the outcome be meaningful for virtually all adults with hearing difficulties and clinicians. Finally, the committee considered the evidence for importance

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⁴ The availability of outcome measures to assess a particular outcome is implicit to this criterion, given that generating evidence of the effect of the intervention on the outcome requires the use of measures. The consideration of the quality of existing measures occurred after the committee determined candidate outcomes.

to measure. To be considered for the core set, the outcome would need to meet all these criteria.

Outcome Measures

After narrowing the candidate core outcomes under consideration, the committee consulted its list of potential measures to recommend. For outcomes with multiple possible measures, the committee initially narrowed the list of outcome measures to be examined primarily based on the amount and quality of available evidence regarding the development and psychometric assessment of that measure. Next, the committee developed a set of criteria for a full evaluation of the remaining candidate measures, which included scientific acceptability (including reliability, validity, and sensitivity to change) and feasibility. The committee carefully reviewed the literature on the psychometrics of each candidate measure, using value judgments regarding the amount and quality of the evidence for each criterion, noting that no single measure had robust evidence for all criteria. Through a series of iterative discussions regarding the available evidence for each measure, the committee determined the final core outcome set and the best existing measure for each core outcome.

RECOMMENDATIONS

Audibility is defined as the ability to detect sound across a broad frequency range and across a range of input levels. Improvement of audibility is expected to be accomplished at the time of the intervention. The particular approach to improving audibility is chosen according to the individual’s type, configuration, and degree of hearing loss and the target of the treatment. Therefore, the measurement of this proximal outcome (to verify that the intervention has been applied successfully) cannot be achieved with a single approach for all contexts and so is not included in the committee’s core set. However, the committee concluded that the improvement of audibility is fundamental to the success of the intervention and requires verification using appropriate methods. Even so, improved audibility alone does not guarantee that the intervention will have the anticipated effect on everyday function; such effects are distal outcomes, and their measurement captures essential aspects of a treatment’s effectiveness. Therefore, the committee’s recommendations relate to measurement of the more meaningful distal outcomes of hearing health interventions.

The following sections describe the committee’s recommendations in five key areas:

1. Core outcome set,
2. Standardized outcome measures,

3. Future research on outcomes,
4. Measure development and refinement, and
5. Uptake of the core outcome set and measures.

Core Outcome Set

As noted earlier, the committee created a comprehensive and clearly defined set of outcomes to be considered for a core outcome set. Significant literature supports several outcomes as being meaningful to adults with hearing difficulties and clinicians, as being associated with hearing difficulties, and as being important to measure. These outcomes are well defined, and adequate measures of the outcomes exist that meet the committee’s criteria to warrant their use in various contexts. In settling on a core outcome set, the committee also considered factors that influence the burden of assessing that set overall (e.g., number of outcomes, availability of measures, mode of administration, time of administration). Table S-1 outlines the committee’s overall conclusion for each outcome considered for the core set.

The committee determined that two outcomes have the strongest evidence for inclusion in a core outcome set: understanding speech in complex listening situations and hearing-related psychosocial health.⁵

Recommendation 5-1:⁶ Individuals and organizations engaged in hearing health interventions should adopt the following outcomes as a core outcome set in both research and clinical settings:

• Understanding speech in complex listening situations
• Hearing-related psychosocial health

The committee emphasizes that this core outcome set should be considered as a foundation for hearing-health outcome assessment following intervention—that is, this set represents the minimum that should be measured across settings and intervention types. This does not imply that other outcomes are not meaningful or should be unexamined.

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⁵ While the term speech in noise is typically used, the committee prefers the use of speech in complex listening situations, which includes understanding speech in a variety of contexts including noisy environments, accented language, multiple speakers, with music playing, and other situations that complicate an individual’s ability to understand speech.

⁶ The committee’s recommendations are numbered according to the chapter of the main report in which they appear. Thus, Recommendation 5-1 is the first recommendation in Chapter 5.

TABLE S-1 Outcomes in Hearing, Communication, and Beyond Considered for the Core Set

Standardized Outcome Measures⁷

Many outcome measures have been developed to assess the outcomes of understanding speech in complex listening situations and hearing-related psychosocial health. The committee focused on the measures with the most available information concerning their psychometric development and use. First, the committee documented the descriptive characteristics of the studies used in each measure’s development, including the population studied, the number of participants, the setting, and how the measure is scored. Next the committee evaluated each measure according to a series of criteria including scientific acceptability and feasibility (by setting).⁸

For the assessment of the outcome of understanding speech in complex listening situations, the committee concluded that both behavioral measures and self-report measures are necessary. While behavioral measures have face validity, are considered by some to be more objective, and are readily available, these measures often lack data on their sensitivity to change and do not necessarily correlate with an individual’s perception of their improvement.

For the self-report measure, the committee narrowed the candidates down to the Abbreviated Profile of Hearing Aid Benefit (APHAB) (and the APHAB-global score in particular) and the Speech, Spatial and Qualities

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⁷ The word standardized is used here in a broad sense to indicate that the same measures are being used for specific outcomes and that there are prescribed materials and procedures for the use of these measures. The committee does not imply that the measures are part of national or international standards.

⁸ See Appendix C for the committee’s detailed evaluation process.

of Hearing Scale (SSQ). While both measures have a sufficient amount of psychometric data regarding the quality of the measure and both are available in multiple languages, the APHAB (and the APHAB-global score in particular) has a greater focus on scenarios of complex listening situations, whereas the SSQ includes a mix of speech, spatial location, and sound qualities. Therefore, the committee concluded that the APHAB-global score currently is the best candidate for assessing an individual’s experience with understanding speech in complex listening environments.

For the behavioral measure, the committee narrowed the candidates down to the Quick Speech-in-Noise (QuickSIN) test and the Words-in-Noise (WIN) test. The QuickSIN, which evaluates an individual’s ability to understand sentences, may be more familiar to audiologists and somewhat shorter to administer. However, psychometric evaluation of the QuickSIN shows more limited evidence on the reliability and consistency of the measurement over time. The WIN, which evaluates an individual’s ability to understand single words, has had a much more rigorous psychometric development and evaluation (including significant evidence for test–retest reliability), is currently used as part of the National Institutes of Health (NIH) toolbox, and is available in Spanish (although additional validation of the Spanish WIN is needed).

For hearing-related psychosocial health, the committee ultimately zeroed in on variations of the Hearing Handicap Inventory (HHI). The well-studied HHI for the Elderly (HHIE) was eliminated primarily because of its length and because psychometric analyses favor the 18-item Revised HHI (RHHI). The shorter screening version (RHHI-S) had less robust research on psychometric strength of the measure. The RHHI, a relatively new measure, has undergone rigorous item analysis but lacks explicit data regarding reliability and sensitivity to change following intervention. Given that 18 of the 25 items included in the HHIE are common to the RHHI, the committee relied on evidence regarding the reliability and sensitivity to change for the HHIE when considering the RHHI.

Overall, current outcome measures are imperfect, but there is adequate evidence to support the standard use of specific measures at this time.

Recommendation 6-1: When assessing outcomes in hearing health, clinicians, researchers, and individuals should use the following outcome measures for each of the outcomes in the core outcome set:

1. Understanding speech in complex listening situations
   1. Abbreviated Profile of Hearing Aid Benefit global score (APHAB-Global)
   2. Words-in-Noise (WIN) test
2. Hearing-related psychosocial health
   1. Revised Hearing Handicap Inventory (RHHI)

The committee recognizes the potential burden of assessing outcomes with three different measures and emphasizes that it will be important to determine the timing and frequency of the outcome measurements that will deliver optimal information. Additionally, it will not necessarily be required to evaluate each measure at each encounter, and self-report measures could be completed by the adult with hearing difficulties in advance of a clinical or research encounter. Finally, the committee reemphasizes that supplemental measures will likely be needed, depending on the specific context of the outcome measurement, including verification of audibility as appropriate.

Future Research on Outcomes

For many of the outcomes of interest, the committee found limited evidence and determined that more research is needed—both to better understand which outcomes are most meaningful for adults with hearing difficulties and for clinicians and also to better define and build the evidence base for these outcomes as potential candidates for an updated core outcome set.

Limited direct research has been performed to determine which outcomes are most meaningful for adults with hearing difficulties and for clinicians. Existing evidence is mostly indirect, as it is usually derived from surveys of satisfaction with interventions or studies of the prevalence and severity of hearing difficulties, and these are typically based on (1) constrained surveys wherein the choices are developed by others (e.g., researchers and clinicians) and (2) varying degrees of direct input from those with hearing difficulties.

Recommendation 4-1: Sponsors of hearing health research should fund additional research to engage adults with hearing difficulties, their communication partners, and clinicians to determine the most meaningful outcomes based on direct evidence from adults with hearing difficulties.

Several meaningful outcomes need further research for various reasons. For example, some outcomes are inconsistently defined, and measurement is inconsistent in terms of the underlying constructs examined. Furthermore, many of the outcomes considered by the committee lack robust evidence on the importance to measure—that is, whether the intervention itself can result in significant clinical change in the outcome, particularly at the level of the individual.

Recommendation 5-2: Sponsors of hearing health research should fund research to build the evidence base on the clinical effect of hearing

health interventions on key outcomes that are meaningful to adults with hearing difficulties and clinicians.

Examples of the types of research needed by outcome are provided in Table S-2.

Additional research will help determine which outcomes might be appropriate for an updated core outcome set. The committee recognizes that while this research is warranted, some outcomes may never rise to the level of a core set to be used across hearing health interventions because the outcome may never be meaningful to all subpopulations. However, this type of research will be useful both for reconsidering outcomes for an overarching core set and also for understanding their use as supplemental outcomes to be measured for specific populations or contexts.

Measure Development and Refinement

The committee recognizes that the measurement of hearing health outcomes requires an improvement in psychometric rigor overall. Research on measure development and refinement is needed to improve the quality of existing measures, including the previously recommended measures. For example, statistical approaches such as item response theory and linking

TABLE S-2 Areas of Needed Research by Outcome

may help with the refinement of existing measures. Additionally, research on sensitivity to change, associations among core outcomes, and variations of existing measures may also help with measure refinement.

Recommendation 6-2: Sponsors of hearing health research should fund further psychometric evaluation of the measures recommended for the core outcome set. Specific areas of research include the following:

1. Development of links and crosswalks
   1. Words-in-Noise (WIN) test versus Quick Speech-in-Noise (QuickSIN) test
   2. Among different variations of the Hearing Handicap Inventory (HHI)
2. Establishment of the sensitivity to change relative to intervention (including minimal detectable change and minimal clinically important difference) for the WIN, the global score from the Abbreviated Profile of Hearing Aid Benefit (APHAB-global), the Revised HHI (RHHI), and the screening (RHHI-S)
3. Development of WIN (and QuickSIN) in other languages
4. Assessment of associations among the set of core outcomes to further establish the independence and uniqueness of each measure
5. Application of item response theory to further develop and refine the recommended outcome measures

Research beyond the currently recommended measures is needed to build evidence for the use of measures not recommended by this committee that might be reconsidered for an updated core outcome set.

Recommendation 6-3: Sponsors of hearing health research should fund research to develop and refine hearing health outcome measures beyond the currently recommended measures, including:

1. Broader psychometric development of the Quick Speech-in-Noise (QuickSIN) test;
2. Exploration of the use of the digits-in-noise test as an outcome measure; and
3. Exploration of the usefulness of high-quality language agnostic tests for sound processing in complex listening situations.

Uptake of Core Outcome Set and Measures

Dissemination and implementation science develops approaches to increasing the uptake of research innovations and of the resulting evidence-based

interventions. Dissemination refers to active efforts to spread information to targeted audiences, while implementation refers to the process of translating that knowledge into action. Both strategies seek to create a change in behavior that leads to the uptake of a new practice—in this case, the use of the core outcome set and corresponding measures when outcome measurement is being undertaken. Several facilitators and barriers have been identified that are specifically related to the uptake of core outcome sets. Facilitators include knowledge of the core outcome set (including its purpose), understanding how to use it and recognizing that its use does not preclude the use of other outcomes, and understanding the rigor of its development. Barriers include lack of awareness, costs, measurement burden, and a preference for continuing current practices.

The first step in encouraging the adoption of the core outcome set and corresponding measures includes engaging in a robust dissemination strategy to ensure that researchers, health care professionals, and adults with hearing difficulties have the necessary awareness and knowledge of the core outcome set and measures.

Recommendation 7-1: Health academic organizations and programs, professional organizations, researchers, and consumer groups should disseminate information about the importance of the core outcome set to clinicians of first contact (e.g., primary care clinicians), hearing health clinicians (e.g., students, audiologists, otolaryngologists), and adults with hearing difficulties.

Strategies for dissemination include providing information and training on the core outcome set and corresponding measures through formal educational, clinical and research-focused training programs, websites, meetings, continuing education, and webinars. The committee notes that disseminating this information to different partners will likely require a multipronged approach. The committee purposefully includes primary care and other clinicians of first contact among the targets of dissemination because these partners will often be the first to evaluate the concerns of patients reporting hearing difficulties. Furthermore, adults with hearing difficulties themselves need to be included in the dissemination efforts to encourage a whole health approach to care.

Dissemination of information alone, however, is insufficient to ensure uptake. It will be important to develop strategies for creating incentives to use the core outcome set as well as strategies for alleviating burdens to its use. Such strategies can come from a variety of sources, including requirements for use in research, incorporation of the outcome measures into electronic health records (to both allow for ease of use by the clinician and to enable patients to answer self-report questionnaires in advance), and use in value-based care.

Recommendation 7-2: To create incentives for the use of the core outcome set and corresponding measures the following should occur:

1. Sponsors of research on hearing health interventions should require the use of the core outcome set and corresponding measures (at a minimum), unless scientifically justified for exclusion.
2. Electronic health record (EHR) vendors should incorporate the Abbreviated Profile of Hearing Aid Benefit and Revised Hearing Handicap Inventory into EHRs.
3. Insurers who require outcome measures should require the use of the recommended measures.

One of the main purposes of developing and using a core outcome set (and corresponding measures) is to allow for the pooling of data to compare the effectiveness of interventions and to develop a more robust evidence base that helps improve clinical care. The committee recognizes that NIH already has existing platforms for the centralized sharing of data.

Recommendation 7-3: To facilitate big data meta-analyses, the National Institutes of Health should develop a national database to allow clinicians and researchers to benchmark the use of the core outcome set and corresponding measures as well as their results.

One highly effective strategy for encouraging the uptake of core outcome sets in other fields is having a central entity take responsibility for developing and updating the core outcome set. The committee recognizes the importance of ensuring the consistency of what is measured and how it is measured over time. However, as new evidence emerges, the core outcome set will need to be revisited. The purpose will not be to just add more core outcomes, but to consider which ones should remain part of the core or which ones should be considered for supplemental measurement, as appropriate. The committee notes that several federal agencies provide substantial funding and work in hearing health research and hearing health care delivery and therefore are well positioned to collaborate to support ongoing evaluation and support for a core outcome set.

Recommendation 7-4: After an adequate level of new research has been gathered, the National Institutes of Health, the Department of Defense, and the Veterans Administration should collaborate to revisit the core outcome set.

Finally, while following the recommendations for dissemination and implementation of the core outcome set can help encourage uptake, there will still likely be gaps in understanding which approaches work best for specific target audiences in the hearing health field.

Recommendation 7-5: Sponsors of hearing health research should fund research on comprehensive implementation science approaches to identify additional key facilitators for and barriers to the uptake and use of the core outcome set and corresponding measures.

CONCLUSION

The development and use of a core outcome set and standardized outcome measures for hearing health interventions in adults will help better determine the effectiveness of various interventions and allow for comparison across interventions, sites, and time. Moving forward, significant investments in research to better define the most meaningful outcomes and improve the rigor of measure development and refinement will be needed to better understand the full functional effect of hearing interventions. Finally, robust and multicomponent approaches to dissemination and implementation that provide incentives for the use of the core outcome set will be key to its uptake. Overall, consistent approaches to outcome measurement that focus on the outcomes that matter the most to adults with hearing difficulties, as well as to clinicians who may be involved in their care, will ultimately improve those individuals’ everyday hearing function.

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