Study links Vision problems and dementia in older adults

Summary: A recent study suggests a significant link between vision problems and dementia in older adults. The study examined nearly 3,000 older people, showing a higher risk of dementia among those with vision problems.

These data support a growing body of research highlighting the link between vision and cognitive disorders. The team’s findings suggest that prioritizing vision health could be a key strategy for mitigating cognitive decline and reducing dementia risk.

Key Facts:

1. The study found that 22% of participants with near vision impairment had dementia, and 33% of those with moderate or severe distance vision impairment had signs of dementia.
2. After adjusting for other health differences, people with moderate to severe problems with distance vision were 72% more likely to develop dementia than those without vision problems.
3. The researchers’ previous work suggested that 1.8 percent of all dementia cases, more than 100,000 of the 6 million Americans with dementia, are likely related to vision loss.

Source: University of Michigan

Losing the ability to see clearly and losing the ability to think or remember clearly are two of the most feared and preventable health problems associated with aging.

Now a new study lends further weight to the idea that vision problems and dementia are linked.

In a sample of nearly 3,000 older adults who took vision and cognitive tests during home visits, the risk of dementia was much higher among those with vision problems – including those who were unable to see well even when wearing their usual glasses . or contact lenses.

The research was recently published in JAMA Ophthalmology by a team from the Kellogg Eye Center at Michigan Medicine, the University of Michigan’s academic medical center.

Based on data from a nationally representative survey of older adults conducted in 2021 through the UM Institute for Social Research, it adds to a growing pile of studies that have suggested a link between vision and dementia.

All of the older adults in the study were over 71, with an average age of 77. They had their near and distance vision, and their ability to see letters that did not contrast sharply with their background, tested by a visiting team member using a digital tablet.

They also took tests of memory and thinking ability and provided health information, including any existing diagnosis of Alzheimer’s disease or another form of dementia.

A good 12% of the entire group had dementia. But that percentage was higher—nearly 22%—among those who had impaired vision to see up close.

In addition, a third (33%) of those with moderate or severe distance vision loss, including those who were blind, had signs of dementia. So did 26% of those who had trouble seeing letters that did not contrast sharply against a background.

Even among those with a mild problem with distance vision, 19% had dementia.

After the researchers adjusted for other differences in health status and personal characteristics, people with moderate to severe problems with distance vision were 72% more likely to have dementia than those without vision problems.

The gaps were smaller, but still large, for other types of visual impairment – except for mild problems with distance vision, where there was no statistical difference.

Those who had more than one type of visual impairment were also 35% more likely to have dementia than those with normal vision.

The new study builds on previous studies that had similar results but relied on self-reported vision abilities rather than objective testing, or were not representative of the US population.

It also builds on previous work on cataract surgery that showed lower rates of dementia over time in adults who had their distance vision restored through surgery.

The authors, led by ophthalmologists Olivia Killeen, MD, MS and Joshua Ehrlich, MD, MPH, write: “Prioritizing vision health may be key to optimizing both vision and overall health and well-being. Randomized trials are warranted to determine whether optimizing of vision is a viable strategy to slow cognitive decline and reduce the risk of dementia.”

But in the meantime, Sheila West, Ph.D., of the Wilmer Eye Institute at Johns Hopkins Medicine, wrote in an accompanying editorial that the new study adds to accumulating evidence about the link between vision and cognitive problems.

“Equitable access to vision care services that prevent, correct, or at least avert the progression of vision loss is a worthy goal regardless of the potential impact on dementia and may be particularly critical for those experiencing cognitive decline,” she wrote.

The study is based on data from the National Health and Aging Trends Study, which is based at the UM Institute for Social Research and the Johns Hopkins University Bloomberg School of Public Health.

Last year, Ehrlich and colleagues published a paper in JAMA Neurology who used another ISR-based study of older adults—the Health and Retirement Study—to estimate the percentage of Americans with dementia whose condition is likely related to their vision loss.

They calculated that 1.8 percent of all cases are vision-related, which equates to more than 100,000 of the 6 million Americans with dementia. This study suggested that visual impairment should be considered alongside other more commonly recognized modifiable dementia risk factors.

This study was funded by the UM Center to Accelerate Population Research in Alzheimer’s (CAPRA) through funding from the National Institute on Aging.

Killeen recently completed the National Clinician Scholars Program at the UM Institute for Healthcare Policy and Innovation and is now at Johns Hopkins. Ehrlich is an assistant professor of ophthalmology and visual sciences at Michigan Medicine and a research associate at ISR, where he is a co-investigator of NHATS, as well as a member of IHPI.

In addition to Killeen and Ehrlich, the study’s authors also include Yunshu Zhou, MS

Financing: In addition to the National Institute on Aging grant supporting NHATS and UM funding supporting the National Clinician Scholars Program, the study was funded by an unrestricted grant to the UM Department of Ophthalmology and Visual Sciences by Research to Prevent Blindness.

About this vision and research news about Alzheimer’s disease

Author: Kara Gavin
Source: University of Michigan
Contact: Kara Gavin – University of Michigan
Image: Image credited to Neuroscience News

Original research: Closed access.
“Objectively measured visual impairment and dementia prevalence in older adults” by Olivia Killeen et al. JAMA Ophthalmology

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Abstract

Objectively measured visual impairment and dementia prevalence in older adults

Importance

Estimates of the association between visual impairment (VI) and dementia in the US population are based on self-reported survey data or measures of visual function that are at least 15 years old. Older adults are at high risk of VI and dementia, so updated national estimates based on objective assessments are needed.

Objective

To estimate the association between VI and dementia in older US adults based on objective visual and cognitive function tests.

Design, setting and participants

This secondary analysis of the 2021 National Health and Aging Trends Study (NHATS), a population-based, nationally representative panel survey, included 3817 respondents aged 71 and older. Data was analyzed from January to March 2023.

Intervention

In 2021, NHATS incorporated tablet-based tests of distance and near acuity and contrast sensitivity (CS) with usual correction.

Main results and measures

VI was defined as distance visual acuity more than 0.30 logMAR, near visual acuity more than 0.30 logMAR, and CS more than 1 SD below the sample mean. Dementia was defined as a score 1.5 SDs or more below the mean in 1 or more cognitive domains, an AD8 Dementia Screening Interview Score indicating probable dementia, or diagnosed dementia. Poisson regression estimated dementia prevalence ratios adjusted for covariates.

Results

Of 2967 included participants, 1707 (weighted percentage, 55.3%) were women, and the median (IQR) age was 76.9 (77–86) years. The weighted prevalence of dementia was 12.3% (95% CI, 10.9–13.7) and increased with near VI (21.5%; 95% CI, 17.7–25.3), distance VI ( mild: 19.1%; 95% CI, 13.0–25.2) ; moderate, severe or blind: 32.9%; 95% CI, 24.1–41.8) and CS impairment (25.9%; 95% CI, 20.5–31.3). Dementia prevalence was higher among participants with near VI and CS impairment than those without (near VI prevalence ratio: 1.40; 95% CI, 1.16-1.69; CS impairment prevalence ratio: 1.31; 95% CI, 1, 04-1.66) and among participants with moderate-to-severe distance VI or blindness (prevalence ratio: 1.72; 95% CI, 1.26-2.35) after adjustment for covariates.

Conclusions and relevance

In this study, all types of objectively measured VI were associated with a higher dementia prevalence. Since most VI is preventable, prioritizing vision health can be important to optimize cognitive function.