Increasing life expectancies around the world are fuelling a steep rise in dementia rates, with 850,000 people believed to be affected in the UK alone. The illness is characterised by progressive confusion and memory loss, beyond what might be expected as an inevitable consequence of old-age. To date, researchers have identified a handful of risk factors for dementia. Now, they believe deteriorating vision could raise the odds of cognitive impairment.
Scientists from the Guangdong Eye Institute in China have identified three eye conditions that could increase the risk of dementia.
According to the researchers, millions of individuals suffering from cataracts, diabetes-related eye disease, and age-related macular degeneration have an increased risk of developing dementia.
The team analysed data from 12,364 British adults aged 55 to 73, who were taking part in the UK Biobank study.
Participants were assessed in 2006 and again in 2010, with their health information tracked until early 2021.
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Over the course of the study, more than 2,300 cases of dementia were documented.
Findings revealed that compared with people who had no eye problems at the start of the study, the risk of dementia was 26 percent higher in those with age-related macular degeneration, 11 percent higher in those with cataracts, and 61 percent higher in those with diabetes-related eye disease.
The research paper, published online in the British Journal of Ophthalmology, stated that the correlation could be down to reduced stimulation of visual pathways in the brain, which could accelerate cognitive decline.
The researchers said: “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.”
While the prevalence of glaucoma among participants appeared to increase the risk of vascular dementia, it did not correlate with higher rates of Alzheimer’s disease.
The incidence of these all three eye conditions increases with age, as do most other risk factors for dementia, which include diabetes, high blood pressure, heart disease, depression and stroke.
The team determined that underlying conditions such as diabetes, heart disease, stroke and depression also increased the odds of dementia.
Researchers noted that risk was highest among individuals suffering some from one of these conditions alongside an eye condition.
They said: “Vision deprivation may result in reduced activation in central sensory pathways, which is associated with a higher risk of cognitive load and brain structure damage.”
The evidence adds to a string of studies that have determined an association between ophthalmic conditions that cause vision impairment and cognitive decline.
Until now, studies probing such associations have been inconclusive, largely because the likelihood of eye conditions rises steeply with age, as do the other accepted risk factors of dementia.
Doctor Sara Imarisio, head of research at Alzheimer’s Research UK, said: “Health problems like diabetes and high blood pressure are linked to an increased risk of dementia and an increased risk of eye condition.
“This study suggests that the association between eye conditions and dementia is not entirely explained by shared underlying risk factors, and that there could be a more direct relationship.”
In the UK, it is believed vision-impairing cataracts affect around half of people over the age of 65, while estimates suggest that around 39,800 people develop age-related macular disease each year.
Diabetic-related eye disease can be broken down into different types. Diabetic retinopathy has been shown to pave the way to other serious eye conditions, notably diabetic macular edema, which affects about one in 15 people with diabetes, according to the National Eye Institute.