An early symptom of dementia has been identified in a new study which it says increases the risk of developing the disease.

As we age, two of the things many of us fear most are the loss of our vision and the loss of the ability to remember things and think clearly. Now, new research has suggested that visual issues and dementia could be connected.

Researchers from the Kellogg Eye Centre at Michigan Medicine, the University of Michigan's academic medical centre, published their findings in JAMA Opthalmology recently. It showed the risk of dementia was higher among people with eyesight difficulties.

This included people who couldn't see well even while wearing their prescription glasses or contact lenses. It consisted of a sample of more than 3,000 older people who took part in vision and cognitive tests during home visits.

The latest research adds to a body of work suggesting there is a link between eyesight and dementia. It's based on data from a nationally representative study of the elderly done in 2021 by the University of Michigan Institute for Social Research.

Those involved in the study were above the age of 71, with an average age of 77. During their tests, a digital tablet was used to assess people's up-close and distant vision, as well as their ability to perceive letters that did not contrast sharply with their backdrop.

Memory and reasoning tests were also carried out and medical information requested, including any previous diagnoses of Alzheimer's or another kind of dementia. One third of those with moderate or severe distant vision impairment, including those who are blind exhibited dementia symptoms.

As did 26 per cent of people who had difficulty seeing letters that didn't stand out against a backdrop. Even among those with minor issues with distant vision, 19 per cent of them developed dementia.

People with moderate to severe distant vision impairment were 72 per cent more likely to have dementia than those with no vision problems. Other types of visual impairment had smaller, but significant, gaps with the exception of modest issues with distance vision, which showed no statistical difference.

Those with many types of vision impairment were 35 per cent more likely to develop dementia than those without any sight issues. The current study expands further on previous research which found similar results, but relied on self-reported visual ability rather than objective testing, or it wasn't representative of the US population.

In the study, the authors said: "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,,"

Sheila West, PhD of the Wilmer Eye Institute at Johns Hopkins Medicine, said the new study adds to growing evidence about the link between vision and cognitive issues. She wrote: "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."