Sensory Loss and Implications for Dementia Testing

Declines in sight and hearing are a natural part of aging, but they can also be associated with mild cognitive impairment and dementia. Some researchers believe dementia alters the way the brain interprets sensory data, while others suspect that the loss of eye and ear nerve impulses is what accelerates cognitive decline. More research is needed to clarify the relationship between dual sensory loss and dementia, but recent studies affirm the connection—and provide hope that early intervention can potentially slow or stop cognitive decline.

Study finds risk of dementia is 86% higher in patients with dual sensory loss

Dementia risk is substantially higher among elderly patients with dual sensory loss, according to Phillip Hwang, MPH and colleagues at the University of Washington. Researchers tracked 2,051 people, ages 75 or older, enrolled in the Gingko Evaluation of Memory Study for seven years and found:

• 11% increased risk of dementia among patients with visual or hearing impairment.
• 86% increased risk of dementia among patients with dual sensory impairment.

Hwang and colleagues concluded that concurrent hearing and vision loss late in life is “strongly associated” with the development of dementia, including Alzheimer’s, and assessing sensory function may help identify those at highest risk of cognitive decline.

Even mild multisensory impairment is associated with cognitive decline

In another study of 1,810 patients ages 70-79, University of California San Francisco researchers identified a link between low sensory function scores and increased risk of cognitive decline and dementia.

• Dementia risk was nearly seven times greater for those in the bottom 25% sensory function scores.
• Just a four point difference in score (out of 12 points) was associated with 68% higher risk of dementia.

Lead researcher Willa D. Brenowitz, PhD, MPH, suggested that treating or correcting some forms of hearing and vision loss early may provide an opportunity for intervention that could reduce or prevent cognitive decline.

Sensory loss intervention may delay or prevent the onset of dementia

Existing research is limited, but University of Michigan researchers associated sensory impairment intervention with better patient outcomes. Elham Mahmoudi, M.B.A, Ph.D. and colleagues tracked 115,000 people over age 66 with hearing loss from 2008 and 2016, with findings published in the Journal of the American Geriatrics Society.

Those treated with hearing aids had:

• 18% lower risk of dementia after three years.
• 13% lower risk of fall-related injury.
• 11% lower risk of depression and anxiety.

Awareness is particularly important, as only 12% of people with diagnosed hearing loss receive hearing aids. Researchers added that it was difficult to tell whether the hearing aid cohort’s results were due to increased physical nerve stimulation in the brain, improvements in social interaction and independence, or both.

To get better patient outcomes, we need better testing

When testing for cognitive decline, particularly in the elderly, there can be confusion as to whether there is mild cognitive impairment or sensory difficulties with the test itself. This experience is not only frustrating for patients, but inconclusive for clinicians. Screening for hearing and sight loss prior to administering a test for cognitive decline is a critical step toward alleviating bias in our testing and ensuring accurate results.

Two MoCA tests differentiate cognitive impairment from sensory issues

While you may have been using the Full MoCA for years, were you aware we offer test adaptations for hearing and visual impairment? If you already know and appreciate MoCA, be sure to check out these versions of the test:

• MoCA-HI: a test designed for patients with hearing impairment
• MoCA-Blind/Telephone: in-person or by-phone testing for patients with visual impairment

Updated test instructions will help you identify subtle differences between mild cognitive impairment and sensory impairments. Like the MoCA you’re using now, these adaptations have been rigorously tested and validated by independent studies.

Researchers affirm the importance and effectiveness of MoCA-HI and MoCA-Blind:

• “The results indicated that the specificity was excellent.” Researchers testing for signs of Alzheimer’s found sensitivity—the ability to correctly identify mild cognitive impairment—decreased slightly without the visual components. However, the 87% specificity—the ability to correctly identify people who did not have mild cognitive impairment—was excellent. Using the recommended adjusted cutoff values provides better sensitivity, researchers noted; MoCA-Blind has a max score of 22, with 19+ considered “normal,” compared to Full MoCA, where patients need to score 26 out of 30 for a normal rating.¹
• “MoCA-HI is easy to administer and reliable for screening cognitive impairment in the severely hearing impaired.” Canadian researchers found that the MoCA test adaptation for the hearing impaired was an effective screening tool, requiring no conversion factor.³
• “Misunderstanding of verbal instructions, cognitive changes, and delayed central processes may lead to a false diagnosis in up to 16% of subjects with hearing loss.” Hearing assessments are not always done as routine parts of geriatric assessment. Yet, researchers from Ruhr-University Bochum found failing to account for sensory impairment in standardized testing can create unfair biases. The use of MoCA-HI can minimize bias in testing people with hearing loss.⁴

Patients with varying degrees of visual or hearing impairment can be effectively tested for signs of Alzheimer’s, dementia, long COVID, heart disease, and ADHD with a high degree of sensitivity using MoCA’s adapted testing content. Visit us online to download our free cognitive screening tools, MoCA-Blind/Telephone for people with visual impairment and MoCA-HI for people with hearing impairment.

References:

1 Walter Wittich, Natalie Phillips, Ziad Nasreddine, Howard Chertkow. Sensitivity and specificity of the Montreal Cognitive Assessment modified for individuals who are visually impaired. Journal of Visual Impairment & Blindness, June 2010, 104(6), 360-368.

2 Kate Dupuis, M. Kathleen Pichora-Fuller, Alison L. Chasteen, Veronica Marchuk, Gurjit Singh & Sherri L. Smith (2015) Effects of hearing and vision impairments on the Montreal Cognitive Assessment, Aging, Neuropsychology, and Cognition, 22:4, 413-437, DOI: 10.1080/13825585.2014.968084

3 Lin, V.Y.W., Chung, J., Callahan, B.L., Smith, L., Gritters, N., Chen, J.M., Black, S.E. and Masellis, M. (2017), Development of cognitive screening test for the severely hearing impaired: Hearing-impaired MoCA. The Laryngoscope, 127: S4-S11. https://doi.org/10.1002/lary.26590

4 Völter, C., Götze, L., Dazert, S., Wirth, R., & Thomas, J. P. (2020). Impact of Hearing Loss on Geriatric Assessment. Clinical interventions in aging, 15, 2453–2467. https://doi.org/10.2147/CIA.S281627

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