Clinical Context

Visual and auditory deficits are associated with significant degrees of disability, and the authors of the current study perform a brief review of the importance of these senses among older adults in particular. Persons at age 65 or older made up 17% of the population in 2020, and this percentage should grow to 23% by 2060. One third of adults between ages 65 and 74 years of age have some degree of hearing loss, as do about one half of individuals aged 75 years and older. Meanwhile, 4% of adults between the ages of 65 and 74 years have visual impairment; this rate increases to 16% among adults at ages 80 to 84 years.

Sensory impairment contributes to cognitive impairment. One study found that peripheral hearing loss at midlife accounted for 9% of dementia cases, making it the largest preventable cause of dementia. Another study found that reductions in visual acuity, contrast sensitivity, and stereo acuity were associated with increases in the risk for cognitive impairment of 55%, 33%, and 28%, respectively. The current study elaborates on the risk for cognitive impairment related to sensory impairment, using a large national sample from the United States.

Study Synopsis and Perspective

Investigators analyzed data on more than 5 million US seniors. Adjusted results show that participants with hearing impairment alone had more than twice the odds of also having cognitive impairment, whereas those with vision impairment alone had more than triple the odds of cognitive impairment.

However, those with dual sensory impairment (DSI) had an 8-fold higher risk for cognitive impairment. In addition, half the participants with DSI also had cognitive impairment. Of those with cognitive impairment, 16% had DSI compared with only about 2% of their peers without cognitive impairment.

"The findings of the present study may inform interventions that can support older people with concurrent sensory impairment and cognitive impairment," lead author Esme Fuller-Thomson, PhD, professor, Factor-Inwentash Faculty of Social Work, University of Toronto, Canada, told Medscape Medical News.

"Special attention, in particular, should be given to those aged 65 to 74 who have serious hearing and/or vision impairment [because] if the relationship with dementia is found to be causal, such interventions can potentially mitigate the development of cognitive impairment," said Dr Fuller-Thomson, who is also director of the Institute for Life Course and Aging and a professor in the Department of Family and Community Medicine and Faculty of Nursing, all at the University of Toronto.

The findings were published online May 2 in the Journal of Alzheimer's Disease Reports.^[1]

Sensory Isolation

"The link between dual hearing loss and seeing loss and mental health problems such as depression and social isolation have been well researched, but we were very interested in the link between dual sensory loss and cognitive problems," Dr Fuller-Thomson said.

In addition, "there have been several studies in the past decade linking hearing loss to dementia and cognitive decline, but less attention has been paid to cognitive problems among those with DSI, despite this group being particularly isolated," she said.

Existing research into DSI suggests an association with cognitive decline; the current investigators sought to expand on this previous work.

To do so, they used merged data from 10 consecutive waves from 2008 to 2017 of the American Community Survey (ACS), which was conducted by the Census Bureau. The ACS is a nationally representative sample of 3.5 million randomly selected US addresses and includes community-dwelling adults and those residing in institutional settings.

Participants aged 65 or older (n = 5,405,135; 56.4% women) were asked yes/no questions regarding serious cognitive impairment, hearing impairment, and vision impairment. A proxy, such as a family member or nursing home staff member, provided answers for individuals not capable of self-report.

Potential confounding variables included age, race/ethnicity, sex, education, and household income.

Potential Mechanisms

Results showed that among those patients with cognitive impairment, there was a higher prevalence of hearing impairment, vision impairment, and DSI than among their peers without cognitive impairment; in addition, a lower percentage of these persons had no sensory impairment (P < .001).

The prevalence of DSI climbed with age, from 1.5% for respondents aged 65 to 74 years to 2.6% for those aged 75 to 84 years and to 10.8% in those aged 85 years and older.

Individuals with higher levels of poverty also had higher levels of DSI. Among those who had not completed high school, the prevalence of DSI was higher compared with high school or university graduates (6.3% vs 3.1% and 1.8%, respectively).

After controlling for age, race, education, and income, the researchers found "substantially" higher odds of cognitive impairment in those with vs those without sensory impairments.

"The magnitude of the odds of cognitive impairment by sensory impairment was greatest for the youngest cohort (age 65-74) and lowest for the oldest cohort (age 85+)," the investigators write. Among participants in the youngest cohort, there was a "dose-response relationship" for those with hearing impairment only, visual impairment only, and DSI.

Because the study was observational, it "does not provide sufficient information to determine the reasons behind the observed link between sensory loss and cognitive problems," Dr Fuller-Thomson said. However, there are "several potential causal mechanisms [that] warrant future research."

Accurate Testing

"The big question is whether we can improve patients' cognitive performance by treating or accommodating their sensory impairments," she said. "If safe and feasible things like hearing aids or cataract surgery improve cognitive health, even a little bit, it would be a huge benefit to society, because sensory loss is very common, and there are many treatment options," Dr Whitson added.

Dr Fuller-Thomson emphasized that practitioners should "consider the full impact of sensory impairment on cognitive testing methods, as both auditory and visual testing methods may fail to take hearing and vision impairment into account."

Thus, "when performing cognitive tests on older adults with sensory impairments, practitioners should ensure they are communicating audibly and/or using visual speech cues for hearing impaired individuals, eliminating items from cognitive tests that rely on vision for those who are visually impaired, and using physical cues for individuals with hearing or dual sensory impairment, as this can help increase the accuracy of testing and prevent confounding," she said.

The study by Dr Fuller-Thomson and colleagues was funded by a donation from Janis Rotman. The investigators have reported no relevant financial relationships. The study by Dr Hwang and colleagues was funded by contracts from the National Heart, Lung, and Blood Institute; the National Institute of Neurological Disorders and Stroke; and the National Institute on Aging. Dr Hwang has disclosed no relevant financial relationships. The other investigators' disclosures are listed in the original article. Dr Reed received grants from the National Institute on Aging during the conduct of the study and has served on the advisory board of Neosensory outside the submitted work. Dr Oh and Dr Whitson have disclosed no relevant financial relationships.

J Alzheimers Dis Rep. Published online May 2, 2022.

JAMA Netw Open. Published online May 5, 2022.

Clinical Implications

• One third of adults between ages 65 and 74 years have some degree of hearing loss, as do about one half of individuals aged 75 years and older. Meanwhile, 4% of adults between the ages of 65 and 74 years have visual impairment; this rate increases to 16% among adults at ages 80 to 84 years.
• The current study suggests that both hearing and vision impairment can raise the risk for cognitive symptoms among older adults, with additive effects in cases of dual sensory impairment. These effects attenuated after age 75 years.
• Implications for the healthcare team: The healthcare team should screen older adults for signs of sensory impairments and implement appropriate interventions when a deficit is discovered.

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