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Accurate Assessment of Hearing and Cognition in Older Adults

McClannahan, Kate AuD, PhD, CCC-A

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doi: 10.1097/01.HJ.0000651560.90484.32
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The number of adults aged 65 and older is projected to double by the year 2060, indicating an unprecedented increase in the number of people with both hearing loss and dementia.1 Thus, accurate hearing assessment of listeners with cognitive difficulties will be critically important to hearing health care in the coming decades. The potential link between hearing loss and dementia further highlights the need to properly measure auditory function and its interaction with cognitive abilities.2 Unfortunately, one often-overlooked issue is how each condition is assessed, both clinically and in research settings. Most previous studies examining the relationship between hearing loss and dementia have determined hearing status via pure-tone audiometry.3-5 Although this method is the gold standard measurement of hearing sensitivity, its accuracy and reliability have not been adequately addressed in older adults with cognitive difficulties. Pure-tone threshold testing requires sustained attention and behavioral responses, which may be difficult for adults with dementia. This is supported by a recent review, indicating that approximately 40 percent of older adults with dementia in each of the reviewed studies were unable to complete pure-tone testing.6 Additionally, the authors noted a general lack of studies examining the ability of adults with cognitive difficulties to complete pure-tone testing.

iStock/ChrisChrisW, Hearing loss, cognition, brain health.

COGNITIVE TESTING

Similarly, the assessment of cognitive function may be confounded by sensory difficulties in adults with hearing loss. Items used during cognitive assessments are often presented verbally, which automatically puts individuals with hearing loss at a disadvantage, particularly those who don't wear hearing aids. For example, the Montreal Cognitive Assessment Test (MoCA)7 screens for mild cognitive impairment and requires an individual to miss no more than four items to pass. The memory subtest of MoCA accounts for five points and consists of five words read aloud at the beginning of the test, which the test taker is asked to remember and recall at the end of the assessment. To complete tests such as MoCA, individuals with hearing loss are disadvantaged by decreased audibility and the need to expend greater listening effort. A failing score and label of mild cognitive impairment, therefore, could be attributable to a sensory rather than a cognitive difficulty. Recent studies have revealed that degraded auditory information (e.g., presence of hearing loss, simulated hearing loss, or background noise) during such assessments results in lower scores and a resultant overestimation of cognitive difficulties.8-10 Therefore, there is a potential risk of mislabeling or overestimating cognitive decline in older adults with hearing loss when the audibility of test items and instructions is not considered.

HEARING TESTS

Parallel challenges exist in assessing hearing sensitivity. Threshold assessment requires participants to sit in an unnaturally quiet and unfamiliar room, listen for very soft sounds played at unpredictable intervals, and respond with a button press, verbal response, or hand raise. For adults with cognitive difficulties, reliably performing such a task may be very challenging because of possible memory issues, difficulty following instructions, and heightened levels of anxiety and irritability.11,12 To further address these issues, our group at Washington University in St. Louis and Saint Louis University is currently assessing the reliability of pure-tone audiometry and other audiologic measures in older adults with and without diagnosed dementia. The goal of this work is to establish the reliability of the methods that are widely used to assess hearing abilities in older adults with dementia and to determine if these methods need any modification. We also hope that this information will help inform clinicians on best practices for the evaluation of hearing loss in older adults with suspected cognitive difficulties.

In summary, assessment of hearing loss and cognitive difficulty in older adults should be conducted with extreme care, taking into account sensory and cognitive limitations that may be comorbid in the aging population. Clinicians need to consider auditory sensory and cognitive difficulties when making diagnoses using tools that may be affected by one or both conditions. Researchers should be mindful of these potential interactions when designing studies on hearing and/or cognitive abilities to avoid misinterpretation of their findings. Critically, to accurately determine the relationship between hearing loss and dementia in the rapidly growing older adult population, we must be confident in the reliability of our assessment measures. Further studies are needed to determine how to accurately measure hearing loss over time in individuals experiencing cognitive decline and how to accurately measure cognitive decline in individuals with diminishing hearing.

REFERENCES

1. Bureau USC. Population Projections. 2017.
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5. Deal JA, Betz J, Yaffe K et al. Hearing Impairment and Incident Dementia and Cognitive Decline in Older Adults: The Health ABC Study. J Gerontol A Biol Sci Med Sci. 2017;72:703-709.
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