Loss of the ability to see clearly and loss of the ability to think or remember clearly are two of the most dreaded 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 had vision and cognitive tests during home visits, the risk of dementia was much higher among those with vision problems – including those who could not see well even when wearing the usual your 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 body of research suggesting a link between vision and dementia.
All of the older people in the study were over the age of 71, with a mean age of 77. They had their near and far vision, as well as their ability to see letters that did not 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 entire group had dementia. But that rate was higher — nearly 22 percent — among those who had impaired near vision.
In addition, a third (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 did not contrast strongly with the background.
Even among those with mild distance vision problems, 19% had dementia.
After the researchers adjusted for other differences in health status and personal characteristics, people with moderate to severe distance vision problems were 72 percent more likely than those without vision problems to have dementia.
The gaps were smaller, but still large, for other types of visual impairment – except for mild distance vision problems, where there was no statistical difference.
Those who had more than one type 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 visual abilities rather than objective tests, or that 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 whose distance vision was 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 vision optimization is a viable strategy to slow cognitive decline and reduce the risk of dementia.”
But in the meantime, in an accompanying editorial, Dr. Sheila West of the Wilmer Eye Institute at Johns Hopkins Medicine wrote that the new study adds to the growing body of evidence on the link between vision and cognitive problems.
“Equitable access to vision care services that prevent, reverse, or at least halt 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 Survey of Trends in Health and Aging, which is based at the UM Institute for Social Research and the Bloomberg School of Public Health at Johns Hopkins University.
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 estimated 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 suggests that visual impairment should be considered alongside other more commonly recognized modifiable risk factors for dementia. This study was funded by UM’s Center to Accelerate Population-Based Research on Alzheimer’s (CAPRA) through funding from the National Institute on Aging.
Killeen recently completed the National Clinical Fellows 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 assistant at ISR, where he is an NHATS co-investigator as well as a member of the IHPI.
In addition to Killeen and Ehrlich, study authors include Yunshu Zhou, MS
In addition to a grant from the National Institute on Aging, which supports NHATS, and funding from UM, which supports the National Clinical Fellowship Program, the study was funded by an unrestricted grant to the UM Department of Ophthalmology and Visual Sciences through Research to Prevent Blindness .
Michigan Medicine – University of Michigan