Loss of vision and loss of capacity to comprehend or recall properly are two of the most feared and avoidable health concerns connected with ageing. New research adds to the evidence that visual issues and dementia are connected.

The risk of dementia was substantially greater among individuals with eyesight difficulties, including those who couldn't see well even while wearing their customary spectacles or contact lenses, in a sample of over 3,000 older persons who performed vision and cognitive tests during home visits.

A team from the Kellogg Eye Centre at Michigan Medicine, the University of Michigan's academic medical centre, reported their findings in JAMA Ophthalmology recently.

It adds to a growing body of research that suggests a relationship between eyesight and dementia. It is based on data from a nationally representative study of older individuals done in 2021 by the University of Michigan Institute for Social Research.

The study's older people were all above the age of 71, with an average age of 77. A visiting team member used a digital tablet to assess their up-close and distant vision, as well as their ability to perceive letters that did not contrast sharply with their backdrop.

They also administered memory and reasoning ability tests and requested medical information, including any previous diagnoses of Alzheimer's disease or another kind of dementia.

One-third of those with moderate or severe distant vision impairment, including the blind, exhibited dementia symptoms. So did 26 per cent of individuals who had difficulty seeing letters that didn't stand out against a backdrop.

Even among individuals with minor issues with distant vision, 19 per cent developed dementia. After controlling all other variations in health status and personal factors, persons with moderate to severe distant vision impairments were 72 per cent more likely to have dementia than those with no vision issues.

Other categories of visual impairment had smaller but still significant gaps, with the exception of modest issues with distance vision, where there was no statistical difference.

Those with many types of vision impairment were 35 per cent more likely to develop dementia than those with normal eyesight.

The current study expands on prior research that found similar results but relied on self-reported visual ability rather than objective testing or was not representative of the US population.

The authors, led by ophthalmologists Olivia Killeen, M.D., M.S. and Joshua Ehrlich, M.D., M.P.H., 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 the 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.