People who develop certain eye conditions are also at increased risk of dementia, according to new research.
Around 1.5million people in the UK suffer with age-related macular degeneration, a condition where a person’s eyesight worsens as they age.
A study of more than 12,000 middle-aged Britons enrolled in the UK Biobank study found people with the condition are 25 per cent more likely to develop dementia.
For people with cataracts, a condition which plagues around one in three people aged over 65 in the UK, the increased risk of dementia is 11 per cent compared to people with no optical health issues.
People with diabetes-related eye disease had a 61 per cent per cent heightened risk of dementia. Glaucoma was not linked to a significant increase in risk.
Dementia accounts for one in nine UK deaths
Dementia is one of the biggest killers in Britain, accounting for one in every nine deaths in 2020, with only Covid (12.1 per cent) claiming more lives last year.
Participants in the study were assessed in 2006 and again in 2010 and followed up until 2021.
More than 2,300 cases of dementia were documented among the participants, according to the experts led by academics from the Guangdong Eye Institute in China.
Researchers also found that people with previous conditions - including diabetes, heart disease, stroke and depression - were also more likely to be diagnosed with dementia.
Risk was highest among people with one of these conditions who also had some form of eye condition, they said.
The authors concluded: "Age-related macular degeneration, cataract and diabetes-related eye disease but not glaucoma are associated with an increased risk of dementia.
"Individuals with both ophthalmic and systemic conditions are at higher risk of dementia compared with those with an ophthalmic or systemic condition only."
The researchers did not look at the underlying mechanisms belying the correlation, and as a result are unable to ascertain causation; it is impossible to conclusively say whether or not eye diseases in some way contribute to dementia, or if they are merely linked.
However, writing in the paper, published Monday in The British Journal of Ophthalmology, the researchers indicate it is unlikely eye diseases cause dementia and that it is more likely the two health issues share a common cause.
“The mechanisms for the positive association between ophthalmic conditions and dementia are largely unknown, but there are several potential pathways for this association,” the researchers write.
“First, ophthalmic conditions are associated with well-known risk factors of dementia including diabetes, stroke, heart disease, hypertension and depression.
“Second, ophthalmic conditions and dementia have many share risk factors including older age, low levels of education, smoking and physical inactivity.”
Vision impairment early sign of condition
Other studies have suggested that vision impairment can be one of the first signs of dementia, and reduced visual stimulation is believed to accelerate its progression.
The study comes as Alzheimer's Research UK said that public willingness to get involved with medical research is at an "all-time high".
The charity said 29 per cent of adults are more likely to consider getting involved in medical research because of the Covid-19 pandemic, according to a poll of 1,000 adults across England, Scotland and Wales.
The survey, released ahead of World Alzheimer's Day on September 21, found that 69 per cent said they would be willing to get involved with dementia research, compared to 50 per cent of a sample of people from a year ago.
"This is positive news for the thousands of studies waiting to get underway to help understand and tackle health conditions like dementia, cancer, and heart disease," said Hilary Evans, chief executive of Alzheimer's Research UK.