What do vision issues have to do with dementia?

A new study involving 3000 older adults, with an average age of 77, suggests that vision problems are linked to dementia.

Researchers from the Kellogg Eye Center at Michigan Medicine, the University of Michigan’s academic medical centre, tested the adults’ 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. All of the older adults in the study were over the age of 71.

In the adults who took vision tests and cognitive tests during home visits, the risk of dementia was much 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.

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. In addition, one-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 didn’t contrast strongly against a background. 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.

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

But in the meantime, in an accompanying editorial, Sheila West, PhD, of the Wilmer Eye Institute at Johns Hopkins Medicine, wrote that the new study adds to accumulating 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.

The research, published recently in JAMA Ophthalmology, builds on previous studies that had similar findings but relied on self-reported vision abilities. 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. The study is based on data from the National Health and Aging Trends Study, which is based at the U-M Institute for Social Research and the Johns Hopkins University Bloomberg School of Public Health.

Image caption: iStockphoto.com/Inside Creative House