May 2021 The Hearing Journal

Cognition is a relevant and emotional topic for our patients. According to the Global Alzheimer's Disease Awareness Survey, 62 percent of adults worry they may develop Alzheimer's disease—a concern that was greater than cancer, stroke, heart disease, diabetes, and arthritis combined. Subjective cognitive decline (SCD), the self-reported experience of worsening or more frequent confusion or memory loss, can be an early sign of dementia. According to the Center for Disease Control and Prevention (CDC), SCD is a growing public health issue. Surprisingly, researchers found few adults with SCD actually discussed their confusion or self-reported memory loss with a health care professional. There are opportunities to increase cognitive screening with these individuals and possibly identify treatable causes. According to the Lancet Commission, hearing loss is the leading modifiable risk for cognitive decline when addressed in midlife. However, individuals with SCD and the general public may be unaware of the effects of hearing loss on cognitive function. “With the growing older adult population and the related increase in the need for health and social services,” noted the CDC, “the public health community is challenged to be proactive.”

screeningSCREENING FOR COGNITIVE DECLINE & HEARING LOSS

It is possible many primary care physicians (PCPs) may not have the time needed to address cognitive screening with patients and may not recognise cognitive impairment until the moderate to severe stage. Studies show many people who are developing cognitive decline do not receive a diagnosis. A Women's Memory Study showed physicians were unaware of cognitive impairment in more than 40 percent of patients with this condition. Because audiologists spend more time with their patients throughout multiple visits, we have an opportunity to implement cognitive screening within our practices and reduce the load for PCPs. Most, if not all, of our professional organisations recognise cognitive screening within our scope of audiology practice.

Several theories may explain the correlation between hearing loss and cognitive decline. Lin and Albert describe common factors such as age, vascular risk (smoking, diabetes), and social factors (education) as well as the effect of hearing loss on increased cognitive load, changes in brain structure and function, and reduced social engagement. The increase in cognitive load results in poor performance on memory and executive function tasks. Because hearing loss and dementia have similar symptoms, recommendations for dementia screening included hearing assessments prior to formal cognitive assessments and testing while wearing appropriate amplification/-modifications.

But what if an audiologist is unable to reach the PCP performing cognitive testing to educate them on the importance of hearing screening before testing? I would like to suggest using non-verbal instructions during cognitive screening as a standard protocol.

BENEFITS OF NONVERBAL SCREENING

Cognitive screening tests are not designed to give a diagnosis, but they are an important first step. The Mini-Mental State Examination (MMSE), the Montreal Cognitive Assessment Scale (MoCA), and Mini-Cog are just a few of the possible cognitive screening tools available. These tests have been accepted and frequently used throughout the medical societies today, but they have substantial drawbacks, specifically, lack of consistency across test sites, low test-retest reliability, and possible biases introduced during testing. These tests can also be expensive, insensitive, time-intensive, highly subjective, and have a potential for human error. Recent research warns us of the possible overestimation of cognitive decline or misdiagnosis of dementia due to age-related hearing loss. These studies evaluated individuals who were free of dementia or any cognitive impairment and presented the verbal cognitive screening instructions through simulated hearing loss. As expected, these individuals performed poorly, leading us to the conclusion that cognitive screening through verbal instructions can lead to misdiagnosis of cognitive impairment in patients with hearing loss. Dupuis, et al., reported that even mild-moderate hearing loss can significantly affect performance on the MoCA. The authors found an increase in normal scores when they removed test items that relied heavily on hearing.

Nonverbal cognitive screening with computerised, self-administered programs, such as Cognivue Thrive, Cogstate, and NeuroTrax, can remove the ears and hearing from the equation and isolate cognition. The instructions and subtests are given visually, with no verbal instructions other than the introductory video. Other benefits include:

  • Removal of bias associated with traditional tests, such as race, education level, and socioeconomic factors that may affect contextual understanding and ability.11
  • Removal of environmental distractions and providing the same testing site each time it is administered.
  • Calibration for vision and dexterity of every patient.
  • No required training or certification.
  • Results being generated automatically and available immediately.

As Wong, et al., stated, “The association between hearing loss and dementia is potentially inflated because of the high reliance on auditory-verbal memory tests to diagnose dementia.” It is important to use nonverbal cognitive testing to reduce the overestimation and possible false positives that occur because of hearing loss and verbal instructions during cognitive screening.

INCORPORATING COGNITIVE SCREENING INTO AUDIOLOGY PRACTICE

A patient's cognitive performance plays an important role in their overall audiologic abilities and assessment. It impacts the patient's ability to process speech, especially in background noise, influences their decision-making process, and affects reaction time and memory. Cognitive performance guides audiologic treatment by enabling the provider to understand and anticipate the needs of patients, supporting the selection and fitting of hearing technology, and allowing for more targeted rehabilitative measures that may contribute to successful outcomes.

Over 15 months ago, I incorporated cognitive screening into my practice primarily because I found the correlation between hearing loss and cognitive decline was a topic that presented itself with every new patient—whether it was a self-diagnosed memory impairment or me educating them on the connection between the two. Having a screening tool that can address the patient's concerns has been a game changer.

Cognitive screening can be used as pre- and post-treatment verification for hearing aid fittings and auditory training to show improvements that occur when we address the hearing loss. It can also be used as a tool with existing patients to confirm we were doing everything we can to help them hear better. Finally, conducting cognitive tests enables me to refer patients for possible cognitive impairment sooner than later.

COGNITIVE SCREENING & HEARING AIDS: CLINICAL INSIGHTS

A study in the Journal of the American Geriatrics Society reported hearing aids may have a mitigating effect on trajectories of cognitive decline later in life, stating that “providing hearing aids or other rehabilitative services for hearing impairment much earlier in the course of hearing impairment may stem the worldwide rise of dementia.” Glick and Sharma demonstrated reversal of cross-modal reorganisation in the brain that occurred after hearing impaired patients were fit with premium hearing technology using real-ear measurements. They also saw improvements in speech-in-noise scores and cognitive function after just six months of hearing aid use. Although improvements in cognitive skills have been observed with hearing aid use, Anderson states “we do not have direct, objective, causal evidence which confirms hearing aid use prevents cognitive decline or improves function.”

Testing this in my practice, we see improvement in cognitive scores in over 60 percent of patients after being fit with hearing aids for the first time. However, we compare that percentage with the number of patients who have worn hearing aids for years and are not performing as well as expected on the cognitive screening. This reminds us hearing loss is not the only contributing factor to cognitive change, and understanding their score has been very helpful in managing the patient's treatment plan.

Since implementing cognitive screening, I have seen a significant value in using the cognitive performance score in association with speech-in-noise testing. I use these two measures pre- and post-hearing aid fitting (using real-ear measures) to monitor the patient's performance. I've learned there is a correlation between the Cognivue Thrive and QuickSIN, to the point where we can predict the patient's outcome with hearing aids and assistive devices. These scores help set appropriate expectations for the patients, determine technology and auditory training in addition to aural rehabilitation programs, improves family counselling on communication strategies, and determines appropriate referrals. Mamo and colleagues also found a correlation between poorer speech-in-noise performance and cognitive problems, regardless of the degree of hearing loss. We will share more of this data in the future.

Audiologists are in a position to include cognitive screening as part of best practices for patient-centred care. Although the research suggests a strong correlation between hearing loss and cognitive decline, several other factors can contribute to a low score on the cognitive screen. Those factors include but are not limited to vision loss, diabetes, hypertension, multiple medications, sleep disorders, chronic anxiety, and depression. It is important to involve the patient's physician in the process so they can address other risk factors associated with possible cognitive decline. Audiologists need a basic understanding of the correlation between hearing loss and cognitive decline but should leave detailed explanations to the physicians.

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