Study: Dementia more common in older adults with vision issues

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Losing the ability to see clearly while also losing the ability to remember and think clearly are among the most dreaded, and preventable, health issues linked with aging.

Now, a new study¹ supports the idea that vision problems and dementia are connected.

In a sample of nearly 3,000 older adults who took vision tests and cognitive tests during home visits, the risk of dementia was higher among those with eyesight problems, including those who weren’t able to see well even when they were wearing their usual eyeglasses or contact lenses.

The research was published recently in JAMA Ophthalmology by a team from the Kellogg Eye Center at Michigan Medicine, the University of Michigan’s academic medical center.¹

According to a Michigan Medical – University of Michigan news release, the study was based on data from a nationally representative study of older adults conducted in 2021 through the University of Michigan Institute for Social Research, and it adds to a growing pile of studies that have suggested a link between vision and dementia.

The UM news release noted all of the older adults in the study were over the age of 71, with an average age of 77. They had their up-close and distance vision, and their ability to see letters that didn’t contrast strongly 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.

Just over 12% of the whole group had dementia. But that percentage was higher – nearly 22% -- among those who had impaired vision for seeing up close, according to the news release.

Moreover, the news release added 33%)of those with moderate or severe distance vision impairment, including those who were blind, had signs of dementia. So did 26% of those who had trouble seeing letters that didn’t contrast strongly against a background.

The news release noted even among those with a mild distance vision issue, 19% had dementia.

After the researchers adjusted for other differences in health status and personal characteristics, people with moderate to severe distance vision issues were 72% more likely than those with no vision issues to have dementia, according to the news release.

Researchers, according to the release, found the gaps were smaller, but still large, for other types of vision impairment – except mild problems with distance vision, where there was no statistical difference.

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

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

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

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

The university noted in the news release Sheila West, PhD, of the Wilmer Eye Institute at Johns Hopkins Medicine, wrote in a recent editorial the UM study adds to mounting evidence about the link between vision and cognitive issues.

“Equitable access to vision care services that prevent, reverse, or at least stave off progression of loss of sight is a worthy goal regardless of the potential impact on dementia and may be especially critical for those experiencing cognitive decline,” she wrote in the editorial.

According to the news release, the study is based on data from the National Health and Aging Trends Study,² which is based at the U-M Institute for Social Research and the Johns Hopkins University Bloomberg School of Public Health.

In 2022, Ehrlich and colleagues published a paper³ in JAMA Neurology that used another ISR-based survey 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, equaling more than 100,000 of the 6 million Americans with dementia. This study suggested that vision impairment should be considered alongside other more commonly recognized modifiable dementia risk factors. That study was funded by the U-M Center to Accelerate Population Research in Alzheimer's (CAPRA) through funding from the National Institute on Aging.

The UM news release noted Killeen finished the National Clinician Scholars Program at the U-M Institute for Healthcare Policy and Innovation and is now at Duke University. Ehrlich is an assistant professor of Ophthalmology and Visual Sciences at Michigan Medicine and a research assistant professor at ISR, where he is a co-investigator of NHATS, as well as a member of IHPI.

In addition to a National Institute on Aging grant that supports NHATS, and the U-M funding that supports the National Clinician Scholars Program, the study was also funded by an unrestricted grant to the U-M Department of Ophthalmology and Visual Sciences by Research to Prevent Blindness.

References:

1. Killeen OJ, Zhou Y, Ehrlich JR. Objectively Measured Visual Impairment and Dementia Prevalence in Older Adults in the US. JAMA Ophthalmol. Published online July 13, 2023. doi:10.1001/jamaophthalmol.2023.2854

2. National Health and Aging Trends Study, accessed August 2, 2023. https://www.nhats.org

3. Ehrlich JR, Goldstein J, Swenor BK, Whitson H, Langa KM, Veliz P. Addition of Vision Impairment to a Life-Course Model of Potentially Modifiable Dementia Risk Factors in the US. JAMA Neurol. 2022;79(6):623–626. doi:10.1001/jamaneurol.2022.0723