The Long-Standing Bilateral Standard: A Historical Perspective
For decades, the audiology community has largely adhered to the recommendation of fitting two hearing aids for individuals presenting with hearing loss in both ears. This standard is rooted in the physiological advantages of binaural hearing. The human auditory system is naturally designed to process sound from both ears, a phenomenon known as binaural summation. This bilateral input offers several key benefits: improved sound localization (pinpointing the direction of a sound source), enhanced speech understanding in noisy environments, reduced listening effort, and a richer, fuller perception of sound quality. These advantages are crucial for navigating complex auditory landscapes and maintaining social engagement.
Despite the intuitive appeal and theoretical benefits, the empirical evidence supporting the superior efficacy of two hearing aids over one, particularly for mild to moderate hearing loss, had surprisingly significant gaps. Much of the existing research dated back to the 1980s and 1990s, utilizing older hearing aid technologies that are far removed from today’s advanced digital devices. Furthermore, these earlier studies often suffered from methodological limitations, including smaller sample sizes, a broad range of hearing loss severities (not specifically focusing on mild to moderate cases common in age-related hearing loss), and inconsistent outcome measures. Critically, these studies frequently observed a notable percentage of participants who, even when offered two devices, ultimately preferred or opted for a single hearing aid. This disconnect between clinical recommendation and patient experience highlighted a pressing need for contemporary, patient-centered research to inform current practice.
The PCORI Mandate: Prioritizing Patient-Centered Outcomes
Recognizing this critical evidence gap and the profound impact of hearing loss on quality of life, the Patient-Centered Outcomes Research Institute (PCORI) stepped in to fund the landmark study. PCORI is an independent, non-profit organization authorized by Congress to fund research that provides patients, their caregivers, and clinicians with reliable information about the health care choices they face every day. A cornerstone of PCORI’s philosophy is the active involvement of patients and stakeholders throughout the research process, from conception to dissemination. This commitment to patient engagement was evident in the Duke study, where Shari Eberts, a prominent patient advocate, served as the lead patient advocate and co-lead of the stakeholder advisory team, ensuring that patient perspectives shaped the study’s design and execution.
The study aimed to address the real-world dilemma faced by countless individuals: balancing optimal hearing rehabilitation with practical considerations like cost and personal preference. The research team recognized that previous studies, which often provided hearing aids free of charge to participants, failed to capture the true decision-making process influenced by financial considerations. By designing a "real-world" trial where participants were responsible for purchasing their hearing aids, the study sought to simulate the authentic choices patients make in clinical settings.
Study Design and Execution: A Real-World Approach
The randomized clinical trial enrolled 275 adults aged 50 and older who had never previously used hearing aids, all presenting with mild to moderate hearing loss, predominantly in the higher frequencies—a common characteristic of age-related presbycusis. Participants were randomly assigned to one of two groups: one receiving a single hearing aid (unilateral fitting) and the other receiving two hearing aids (bilateral fitting). The parallel group design ensured that direct comparisons could be made between the two intervention strategies.
A distinctive feature of this study was its commitment to a real-world scenario regarding cost. Unlike prior research where devices were often subsidized or free, participants in this trial paid for their hearing aids and associated audiology services. This critical design element allowed the researchers to assess not only the clinical benefit but also the impact of financial considerations on patient choices and satisfaction. While an industry partner, Phonak, provided a modest discount on the devices, the financial outlay remained a significant factor for participants, mirroring the actual consumer experience.
The primary outcome measure for the study was self-reported hearing aid benefit, assessed using a standardized, validated questionnaire known as the Abbreviated Profile of Hearing Aid Benefit (APHAB). The APHAB is widely recognized for its ability to capture a patient’s perception of their hearing difficulties and the benefit they derive from amplification in various listening situations. This patient-reported outcome (PRO) approach aligns perfectly with PCORI’s emphasis on measuring what truly matters to patients. Participants were followed for three months, after which their self-reported benefit and final hearing aid choices were evaluated.
Key Findings: A Modest Advantage, Significant Implications
After three months of hearing aid use, the study found that participants fitted with two hearing aids reported approximately 5% greater benefit on the primary outcome measure compared with those fitted with one. This difference was statistically significant, confirming that bilateral amplification does, on average, offer a superior self-perceived benefit. However, a crucial finding was that both groups experienced improvement relative to their baseline, underscoring that even a single hearing aid provides meaningful benefit for individuals new to amplification.
Perhaps one of the most compelling insights from the trial was the ultimate choice made by participants. Despite the measured 5% average benefit from two hearing aids, a substantial 29% of participants ultimately chose to use only one hearing aid. This significant percentage highlights the complex interplay of factors beyond pure audiological benefit that influence patient decisions, including personal preference, comfort, lifestyle, and, notably, cost.
Dr. Smith emphasized the nuance of these findings: "Two still dominates. Most people are performing better; they perceive they’re performing better… So I do believe that patients should still consider two compared to one. However, if somebody could only afford one… one still provided benefit." This statement encapsulates the study’s balanced conclusion: while bilateral fitting remains the general recommendation, unilateral fitting is a viable and beneficial option for a significant minority of patients.
The Role of Affordability and the Rise of OTC Hearing Aids
The study’s real-world financial model highlighted the undeniable impact of cost on hearing aid adoption and choice. Hearing aids represent a significant investment, often ranking among the largest purchases individuals make after a home or car. The lack of comprehensive insurance coverage for hearing aids and associated services in many regions exacerbates this financial burden. Dr. Smith advised consumers to ask detailed questions about pricing models, understanding whether costs bundle devices and services, and to explore insurance benefits thoroughly. The availability of different technology levels (basic, mid-range, premium) also offers flexibility, suggesting that two entry-level devices might be more affordable than one high-end device, a point audiologists should convey to patients.
The conversation around affordability naturally extends to the emerging market of over-the-counter (OTC) hearing aids. Following the FDA’s landmark ruling in October 2022, OTC hearing aids are now available for adults with perceived mild to moderate hearing loss without a prescription or professional fitting. While the Duke study predated the widespread availability of OTC devices, its findings are highly relevant. For individuals considering OTC options, particularly those weighing two OTC devices against one professionally fitted device, the study suggests that even a single device can provide benefit. However, Dr. Smith cautioned that OTC devices are best suited for technologically savvy individuals without "red flags" (e.g., sudden hearing loss, ear pain) and who are capable of self-fitting. While OTCs offer a more accessible entry point to amplification, they also come with a higher reported return rate compared to prescription-fitted aids, underscoring the value of professional guidance.
Implications for Clinical Practice: Evolving Recommendations
For audiologists, the study reinforces the traditional recommendation of bilateral hearing aids as the standard of care but also provides robust evidence to support more nuanced, patient-centered discussions. While audiologists will likely continue to advocate for two devices due to the observed additional benefit, they now have stronger data to acknowledge the validity of a patient’s choice for one hearing aid, particularly when cost or personal preference is a significant factor.
The study champions the integration of patient-reported outcome measures, such as the APHAB, into routine clinical practice. By systematically assessing a patient’s self-perceived benefit, clinicians can gain a deeper understanding of individual experiences and tailor recommendations more effectively. Dr. Smith also hinted at future research exploring potential predictive measures, such as assessments of hearing handicap or auditory working memory, which could help audiologists more confidently predict which patients might genuinely prefer or benefit sufficiently from a single device. This move towards personalized audiology is critical, as every patient’s experience with hearing loss and amplification is unique.
The Indispensable Role of Patient Engagement
One of the most profound takeaways from the study was the transformative impact of patient involvement. PCORI’s requirement for patient engagement proved invaluable, with Shari Eberts and other stakeholders contributing significantly to all phases of the research. Patient input influenced the selection of outcome measures, the wording of patient-facing materials, and even critical decisions regarding the study’s timeline. Notably, the patient advisory group’s insights during the COVID-19 pandemic led to a delayed launch, acknowledging that altered social behaviors (e.g., reduced restaurant visits, increased home time) would skew initial data on hearing aid benefit in "real-world" situations. They also prompted the inclusion of a questionnaire to assess the impact of masking and social distancing on participants’ experiences, ensuring a more accurate interpretation of results.
Dr. Smith passionately stated that this experience fundamentally changed her approach to research, leading her to include individuals with lived experience as equal partners in all subsequent studies. This "nothing about us without us" philosophy ensures that research addresses questions most relevant to patients and yields findings that are truly impactful for their lives.
Limitations and Future Research Directions
As with any scientific endeavor, the Duke study has its limitations. The parallel group design, while rigorous, did not incorporate a crossover element where participants could experience both one and two hearing aids. A crossover design might have provided even richer data on individual preferences and comparative benefits. The study’s three-month duration also represents a relatively short follow-up period; longer-term studies could provide insights into sustained benefit and adaptation. Furthermore, the focus was primarily on hearing-related outcomes, with less emphasis on broader impacts such as social participation, quality of life, or cognitive load, which are significant aspects of living with hearing loss.
Future research will aim to address these limitations and delve deeper into unanswered questions. A critical area of inquiry is the clinical significance of the observed 5% difference in benefit. While statistically significant, researchers need to determine if this difference translates into a meaningful improvement for individual patients. Further investigation into predictive markers that could guide individualized recommendations at the point of care is also paramount. Ultimately, the goal is to move beyond a one-size-fits-all approach towards truly personalized hearing healthcare.
Broader Impact and a New Era of Informed Choice
The Duke University study represents a pivotal moment in audiology. It provides the strongest contemporary evidence yet to inform the "one vs. two hearing aids" debate, moving the conversation from intuition and anecdotal experience to data-driven insights. For patients, it empowers them with robust information to engage in shared decision-making with their audiologists, considering not only clinical benefit but also personal values, lifestyle, and financial realities. For audiologists, it offers a scientific basis for more flexible and patient-centered counseling, acknowledging that optimal care involves respecting individual choices, even when they diverge from traditional recommendations.
In an era of increasing healthcare consumerism and the burgeoning OTC market, this research is more relevant than ever. It underscores that while technology continues to advance, the human element—patient experience, preference, and the complexities of real-world decision-making—remains central to effective and equitable hearing healthcare. The study is a testament to the power of patient-centered research in shaping clinical guidelines and ultimately improving the lives of millions affected by hearing loss.
