Optimizing Hearing Aid Fittings for Older Adults

Introduction

The global demographic landscape is undergoing a profound transformation, characterized by a rapidly aging population. Projections from the World Health Organization and the United Nations Department of Economic and Social Affairs indicate a substantial rise in the number and proportion of older adults in the coming decades. By 2050, the percentage of the population aged 65 and over is expected to increase from 10% to 16%. Even more strikingly, the number of adults over 65 is projected to double, and those over 80 are expected to triple (World Health Organization, n.d.; United Nations Department of Economic and Social Affairs, Population Division, 2022). This demographic shift, driven by advancements in healthcare and healthier living, presents both opportunities and challenges for audiology, as hearing loss is highly prevalent in this age group.

Beyond the peripheral auditory system, aging also brings about changes in cognitive function. It is crucial for audiologists to understand how these cognitive changes interact with hearing loss, as they can significantly impact a patient's ability to process sound, understand speech, and successfully adapt to hearing aid technology. This article aims to provide a comprehensive overview of these age-related auditory and cognitive changes and offer practical, evidence-based guidance for optimizing hearing aid fittings for older adults. The discussion will emphasize strategies to enhance speech audibility, preserve critical temporal cues, and reduce listening effort, ultimately contributing to improved patient outcomes and a better quality of life.

Learning Outcomes

After this course, participants will be able to:

• Describe how aging affects auditory processing.
• List 3 important amplification characteristics to consider when fitting older adults.
• Describe how Phonak technology supports evidence-backed fitting recommendations.

Auditory Processing and Cognitive Changes with Aging and the Impact on Speech Perception

The Complexity of Auditory Processing

Auditory processing is a highly intricate cognitive function that extends far beyond the mere detection of sound. It involves a complex interplay of various brain regions responsible for encoding different dimensions of auditory information. As sound travels from the periphery to the auditory cortex, it undergoes multiple stages of processing. Different neural populations respond to distinct aspects of sound, such as loudness, rhythm, and temporal patterns. This information is then integrated to allow for the differentiation of sounds, the recognition of words, the understanding of phrases and sentences, and the comprehension of grammar and meaning (Windle et al., 2023). This elaborate network of neural connections is fundamental to successful speech perception.

Age-Related Changes in the Brain and Auditory Processing

A fundamental aspect of normal aging is physiological change within the brain, including a reduction in neural connections (Windle et al., 2023). These age-related neurological alterations can significantly affect auditory processing capabilities. Specifically, older adults may experience declines in:

• Processing of timing information: The ability to precisely track rapid changes in sound.
• Gap detection: Identifying the brief silences or pauses between sounds or speech elements.
• Localization: Accurately determining the origin of a sound, which relies on interaural time and level differences.
• Frequency perception: The fine-grained discrimination of different pitches.

These declines collectively make it more challenging for older adults to extract specific sounds from a complex acoustic environment, focus on a particular speaker, and understand speech clearly, especially in the presence of background noise (Windle et al., 2023).

Temporal information is particularly critical for speech perception, conveyed across different frequency bands. The speech envelope (below 50 Hz) provides cues about overall amplitude fluctuations. Voicing and periodicity (50-500 Hz) contribute to speech clarity, while temporal fine structure (above 500 Hz) is essential for the fine-grained details of speech sounds, such as pitch and formants (Windle et al., 2023). Hearing loss itself challenges the brain's ability to utilize these spectral and temporal cues, exacerbating the difficulties faced by older adults.

Theories Behind Changing Cognitive Abilities

The auditory system's role is to process and deliver sound, but it is the cognitive system that interprets and assigns meaning to these sounds. Windle et al. (2023) highlight three primary theories that attempt to explain age-related cognitive changes and their impact on auditory processing:

1. Processing-Speed Theory: This theory posits that mental processing slows down with age. This deceleration demands more mental resources, making it harder for individuals to recall past events or initiate complex tasks. The cognitive system becomes less efficient, requiring more effort for tasks that were once automatic.
2. Working Memory Theory: Working memory is the system responsible for temporarily storing and manipulating information relevant to a current task. It has a limited capacity. As individuals age, this capacity may diminish, or the efficiency with which information is processed within working memory may decline. An overloaded working memory can lead to difficulties in performing tasks, analogous to a computer with insufficient RAM (Windle et al., 2023).
3. Inhibition Theory: This theory suggests that older adults experience a reduced ability to filter out irrelevant information. This diminished inhibitory control can clutter working memory with extraneous stimuli, further limiting its capacity for relevant information. The inability to selectively attend to target signals while suppressing distractors significantly impacts speech understanding in noisy environments (Windle et al., 2023).

While these theories offer distinct explanations, it is likely that a combination of these factors contributes to the observed cognitive declines in older adults. Meta-analyses have shown correlations between speech-in-noise (SIN) performance and various cognitive functions, including processing speed, inhibition, working memory, and episodic memory (Dryden et al., 2017). These cognitive domains are known to decline with age, and their additive effects can profoundly impact listening ability.

Increased Listening Effort and its Consequences

A significant consequence of age-related auditory and cognitive changes is an increase in listening effort. Listening effort refers to the mental energy or attention expended to understand speech. This effort is finite and varies depending on the difficulty of the listening task and the individual's motivation (Windle et al., 2023). When cognitive resources are strained, more effort is required to process auditory information, leading to increased listening fatigue.

Evaluating and addressing listening effort is crucial because it directly influences:

• Motivation to comply with treatment: Patients who experience less fatigue and strain with their hearing aids are more likely to wear them consistently.
• Willingness to engage socially: Reduced listening effort can empower older adults to participate more actively in social situations, which is vital for maintaining social connections and overall well-being (Windle et al., 2023).

While hearing aids cannot "cure" hearing loss, they are highly beneficial in addressing peripheral sensitivity loss, enhancing the signal-to-noise ratio (SNR), and suppressing distracting noise. By doing so, hearing aids can significantly reduce listening fatigue and improve a patient's quality of life (Windle et al., 2023).

Limitations of Clinical Tests in Guiding Specific Settings

Despite the clear links between hearing loss and cognitive function, there is currently no precise formula to dictate specific hearing aid settings based on cognitive test results. Cognitive tests, particularly those relying on verbal instructions, can be influenced by hearing loss, and their direct clinical utility for informing hearing aid programming remains uncertain (Windle et al., 2023). Similarly, standard speech audiometry, while providing insights into overall auditory ability, does not directly inform specific hearing aid settings or preferences (Windle et al., 2023).

Therefore, the approach to fitting older adults must prioritize patient-centered care. Audiologists should incorporate patient input and apply evidence-based principles to optimize hearing aid settings. The primary goal is to provide the clearest possible sound, minimizing distortion to support cognitive processing.

Considerations and Practical Guidance for Selecting and Fitting Older Adults with Hearing Aids

Optimizing hearing aid fittings for older adults requires a multi-faceted approach that considers the unique challenges posed by age-related auditory and cognitive changes. The following sections outline evidence-based principles and practical guidance for audiologists.

Optimizing Compression Settings

Compression is a fundamental aspect of hearing aid processing, influencing how sounds of different intensities are amplified. For older adults, careful consideration of compression speed and ratios is paramount to ensure audibility without compromising speech clarity.

Compression Speed: Fast-Acting vs. Slow-Acting

Fast-acting compression (FAC) is characterized by short attack and release times. This rapid response allows for the preservation of audibility for soft speech signals and can provide clarity for low-input levels (Gatehouse et al., 2006; Kowalewski et al., 2017; Moore et al., 2011). However, FAC can also have detrimental effects:

• Distortion of speech envelope cues: The rapid gain changes can distort the natural amplitude fluctuations of speech, making it sound "mushy" (Windle et al., 2023).
• Amplification of noise in gaps: Quick release times can amplify background noise during the quiet intervals between speech elements, hindering gap detection and increasing listening effort (Windle et al., 2023).
• Reduced modulation detection: This can impair the ability to separate individual speakers in complex environments (Windle et al., 2023).
• Impaired sound localization: Especially in reverberant conditions (Windle et al., 2023).
• Reduced spectral contrast: Increasing frequency channels in FAC can diminish the distinctiveness of different sounds (Windle et al., 2023).

Slow-acting compression (SAC), conversely, utilizes longer attack and release times. This results in a more gradual gain change, offering several advantages:

• Increased comfort: Particularly in noisy situations (Gatehouse et al., 2006; Moore et al., 2011).
• Better speech understanding in noise: SAC can be more effective than FAC in helping the brain understand speech clearly in challenging listening environments (Windle et al., 2023).
• More spatial contrast: Contributes to better loudness comfort (Hassager et al., 2017).

Research by Gatehouse et al. (2006) investigated the interaction between cognitive function and compression speeds. They found that while FAC offered superior speech intelligibility under ideal conditions, its benefits declined significantly with poorer signal-to-noise ratios (SNR) and higher speech levels. Crucially, SAC demonstrated more consistent performance across all cognitive levels, providing greater comfort and being preferred by users, especially those with reduced cognitive abilities.

Given these findings, an adaptive compression approach that combines the benefits of both fast and slow-acting compression is optimal. Phonak's Adaptive Phonak Digital (APD) 3.0 utilizes adaptive compression, featuring a fast attack for comfort and a slow release that adapts to the acoustic environment. This approach provides:

• More dynamic range: Allowing for a wider range of audible sounds (Hassager et al., 2017).
• Reduced perceived reverberation: Improving clarity in echoic environments (Hassager et al., 2017).
• Enhanced comfort in noise and for impulsive sounds: Contributing to a more comfortable listening experience (Kowalewski et al., 2017; Lopez-Poveda et al., 2017).

In quiet situations, APD uses adaptive compression to maximize audibility cues. In noisier environments, it employs a mix of adaptive and slow compression (40% adaptive, 60% slow) to leverage the benefits of slow compression in noise while maintaining temporal cues. This adaptive compression is the default for all Phonak adult fittings since APD 2.0 (introduced with Paradise technology), automatically optimizing gain for patients.

For patients with reduced cognitive abilities who may benefit from even slower compression, Phonak Target software offers "Adaptive Phonak Digital Contrast 3.0" as a fitting formula option (Figure 1). This proprietary setting applies slow compression in all environments, providing more temporal envelope cues. It is a clinician-selected option, not a default, allowing for tailored adjustments based on individual patient needs.

Figure 1. Fitting formula options are found in the Global Tuning tab

Compression Ratios

Compression ratios define the relationship between input and output levels. While higher ratios can make soft inputs audible without being uncomfortably loud, they can also:

• Reduce intelligibility in noise: Although they may improve intelligibility in quiet (Windle et al., 2023).
• Distort speech envelope cues: Potentially impairing consonant recognition and overall speech recognition (Windle et al., 2023).

Research indicates that listeners generally prefer lower compression ratios (typically ≤2.0) for speech quality, especially in noise (Windle et al., 2023). Phonak Target software displays compression ratios, which typically fall within this preferred range. For patients requiring a more linear amplification approach, the "Global Tuning" feature allows clinicians to select "Semi-linear" or "Linear" compression (Figure 2). While full linear compression is rarely used, semi-linear can be beneficial, maintaining gain for average speech (G65) while adjusting gain for soft (G50) and loud (G80) sounds.

Figure 2. Compression options in the Global Tuning tab

Furthermore, with APD 2.0, Phonak introduced an additional kneepoint for loud sounds, automatically providing:

• Loudness comfort at high input levels: Preventing discomfort from sudden loud sounds (Lopez-Poveda et al., 2017).
• Improved speech intelligibility for loud speech in noise: Enhancing clarity in challenging loud environments.
• Greater flexibility in fine-tuning: Allowing for more precise adjustments of soft, mid, and loud speech targets.

In summary, optimizing compression for older adults involves utilizing adaptive compression algorithms, defaulting to slow-acting compression in noisy environments (or using APD Contrast for those with greater cognitive needs), and minimizing compression ratios or choosing semi-linear/linear options where appropriate.

Choosing Binaural Processing or Considering Unilateral Aiding

The brain's ability to process interaural timing and level differences (ITDs and ILDs) declines with age, making it harder to separate sounds from background noise (Windle et al., 2023). Binaural processing in hearing aids, where the two devices share audio signals, can integrate these timing and level cues to form a unified spatial representation of sound. This integration offers significant benefits:

• Enhanced ability to distinguish target voice from background noise: Improving the signal-to-noise ratio (SNR) (Derleth et al., 2021).
• Reduced cognitive effort: By improving sound separation and focus (Derleth et al., 2021).

Phonak's StereoZoom feature, for instance, leverages binaural processing to create a narrower beam, functioning as a four-microphone system. StereoZoom 2.0, with its smooth activation, intelligently adapts the beamforming to optimize speech understanding in various challenging environments.

While binaural fitting is generally preferred due to its numerous advantages, a small subset of older adults may experience binaural interference, where processing sounds from both ears simultaneously makes listening more challenging (Mussoi & Bentler, 2017). In such rare cases, a unilateral fitting might yield better performance. To evaluate this, clinicians can measure speech intelligibility in noise and listening comfort in three configurations: binaural, left monaural, and right monaural. This can be done in sound field testing using materials like the Hearing in Noise Test (HINT) or the Connected Sentences Test (CST), with speech from the front and noise from the back (Windle et al., 2023; Mussoi & Bentler, 2017). If performance drops with binaural hearing aids and improves with a monaural fit, unilateral aiding may be considered.

Using Noise Management and Advanced Features to Improve SNR

Improving the signal-to-noise ratio (SNR) is critical for reducing listening effort and freeing up cognitive resources. Phonak's SmartSpeech™ Technology is a collection of features designed to adaptively and seamlessly enhance speech understanding and reduce listening effort across various listening environments.

Speech Enhancer

Patients spend a significant amount of time in calm or quieter situations. Speech Enhancer provides an adaptive boost to soft voices in these quiet environments. This feature is particularly beneficial for hearing soft-spoken individuals (e.g., grandchildren, a spouse with a quiet voice) or speech at a distance. By selectively amplifying soft speech without increasing overall gain, Speech Enhancer avoids amplifying unwanted ambient sounds like footsteps or air conditioning.

Studies on Speech Enhancer have shown remarkable benefits:

• 34% less listening effort overall (Latzel et al., 2024).
• 45% less listening effort with speech from a distance (Habicht & Schuepbach-Wolf, 2024).
• 21% less fatigue at the end of the day (Latzel et al., 2024).
• Improved memory and comprehension performance (Latzel et al., 2024).

This feature, available in Phonak's 90-level technology, directly supports cognitive function by reducing the strain of listening in common daily scenarios.

Directional Microphone Technology (StereoZoom 2.0 and SpeechSensor)

Directional microphones are a cornerstone of noise management in hearing aids, significantly improving SNR and speech intelligibility in noisy environments (Woodward & Latzel, 2022). For every 10 dB of hearing loss, a wearer may require an additional 1-3 dB of SNR to maintain their unaided intelligibility (Dillon, 2012). Directional microphones provide a foundational improvement in SNR, with studies showing up to 26% better speech understanding compared to unaided listening in individuals with moderate to severe hearing loss (Woodward & Latzel, 2022).

Phonak's StereoZoom 2.0, combined with SpeechSensor (in 90-level technology), takes directional microphone technology further. SpeechSensor intelligently detects the direction of speech (front, side, or back) and adjusts the beamforming accordingly. This adaptive system provides:

• 3 dB better SNR when speech is from the front in challenging environments (Woodward et al., 2022).
• 3.4 dB better SNR with fixed directionality when speech is from the side (Woodward et al., 2022).
• 2.5 dB better SNR with Real-Ear Sound when speech is from behind (Woodward et al., 2022).

This comprehensive approach ensures that patients have access to sound from all directions, reducing listening effort and improving clarity regardless of the speaker's position (Pichora-Fuller & Singh, 2006).

Noise Reduction Settings

While noise reduction algorithms enhance listening comfort and sound quality, their impact on speech intelligibility can be complex. Aggressive noise reduction settings, especially fast-acting ones, can sometimes distort speech signals or remove crucial speech components, forcing the listener to work harder to process the remaining signal (Windle et al., 2023).

Windle et al. (2023) recommend starting with moderate noise reduction settings. This approach improves listening comfort without significantly affecting speech intelligibility. Stronger noise reduction levels may be acceptable for individuals with higher cognitive scores, but for those with lower working memory abilities, a moderate setting helps balance the reduction of cognitive load without introducing new processing challenges. Clinicians can adjust these settings in the Phonak Target software under the "Program options" (Figure 3).

Figure 3. Program Options houses noise reduction like NoiseBlock, SoundRelax, Dynamic Noise Cancellation, etc.

DEEPSONIC and Spheric Speech Clarity

A significant advancement in noise management comes with Phonak's Audéo Sphere Infinio devices, featuring the dedicated real-time AI/Deep Neural Network (AI/DNN) DEEPSONIC chip. This chip boasts 4.5 million neural connections and 53 times more processing power than current industry chip technology (Wright et al., 2024).

This powerful processing supports Spheric Speech Clarity, a feature that extracts, enhances, and integrates speech in real-time from any direction, in any situation. Spheric Speech Clarity reinforces the speech signal while significantly reducing background noise, allowing speech to "pop" and become more discernible. This technology expands access to speech from any direction and significantly reduces listening effort in challenging environments (Wright et al., 2024).

Comparative studies show that Audéo Sphere provides up to 3.7 dB more SNR benefit compared to key competitors in realistic sound environments where noise and speech originate from various directions (Raufer et al., 2024). This translates to patients being up to two times more likely to hear and understand every word from any direction, representing up to a 36.7% increase in speech understanding compared to other brands' devices (Raufer et al., 2024; Wright et al., 2024). The ability to withstand almost 3 dB poorer SNR without an increase in subjective listening effort highlights the profound impact of Spheric Speech Clarity on a patient's daily life and social engagement.

Roger Technology

For patients with a greater need for SNR improvement in high-noise environments or over distance, remote wireless microphones like Roger should be considered. Roger technology provides exceptional speech understanding in group conversations and over distance due to its adaptive gain (Thibodeau, 2020). As noise levels increase, Roger automatically increases the signal of the target speaker to maintain a positive SNR.

The Roger On microphone, in particular, offers flexibility and ease of use, even for patients with cognitive decline. Its intuitive design allows users to simply place it on a table for group conversations, clip it on a single speaker for one-on-one interactions, or point it at a speaker in a noisy environment. This user-friendly interface ensures that patients can easily leverage the benefits of remote microphones to achieve optimal speech understanding and reduced listening effort in various challenging situations.

Conclusion

The growing population of older adults, coupled with the inevitable age-related changes in auditory processing and cognitive function, presents a compelling need for optimized hearing aid fittings. While normal aging involves some cognitive decline that can impact speech perception and increase listening effort, audiologists have a crucial role in mitigating these challenges through evidence-based practices and advanced hearing aid technologies.

Key principles for optimizing fittings include:

• Making speech audible with minimal distortion to the envelope and maintaining quiet gaps between speech elements: Achieved through adaptive compression algorithms like Phonak's Adaptive Phonak Digital, with options for slower compression (APD Contrast) and linear gain adjustments.
• Preserving interaural timing and level differences, and considering unilateral aiding if binaural interference is noted: Supported by binaural processing features like StereoZoom 2.0, while acknowledging the rare cases where monaural fitting may be more beneficial.
• Using directionality and noise reduction settings to improve SNR and minimize cognitive load: Enhanced by Phonak SmartSpeech™ Technology, including Speech Enhancer for soft voices in quiet, adaptive directional microphones (StereoZoom 2.0 and SpeechSensor), and the groundbreaking Spheric Speech Clarity powered by DEEPSONIC. Remote microphones like Roger further extend these benefits in highly challenging environments.

By consistently applying these principles and leveraging advanced technologies, audiologists can empower older adults to not only hear better but also live better, reducing listening effort, improving cognitive resource allocation, and fostering greater social engagement. The commitment to providing the clearest possible sound, tailored to the individual needs of each patient, is paramount to their success and overall well-being.

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