Age-related macular degeneration, cataracts and diabetes-related eye diseases are associated with an increased risk of dementia, according to a new study.
Visual impairment can often be one of the first signs of dementia, the researchers said. Some small studies have linked ophthalmic conditions that limit vision to cognitive decline. They include age-related macular degeneration, cataracts, diabetes-related eye diseases, and glaucoma.
These eye conditions worsen with age as do other systemic illnesses, such as diabetes, high blood pressure, heart disease, depression, and stroke, all of which are established risk factors for dementia.
For this study, the researchers wanted to see if these eye conditions were linked to an increased risk of any cause of dementia, regardless of systemic diseases. They found that’s true for age-related macular degeneration, cataracts, and diabetes-related eye diseases, but not glaucoma.
Age-related macular degeneration increased the risk of dementia by 26% compared to people without the condition. Likewise, cataracts increased the risk by 11% and diabetes-related eye diseases increased it by 61%.
Although glaucoma was not associated with an increased risk of Alzheimer’s disease, the most common form of dementia, it was associated with an increased risk of vascular dementia, a type of dementia caused by problems with the blood supply to the brain.
Participants were asked if they had ever experienced a heart attack, angina or stroke, or if they had developed high blood pressure or diabetes. They were also evaluated for depression.
Those systemic conditions were associated with an increased risk of dementia, and when a person also had an ophthalmic condition, that risk increased even more. Participants with age-related macular degeneration and diabetes were at the highest risk.
Data for this latter study were obtained from the UK Biobank study. It included data from 12,364 adults aged 55 to 73 years. Of these, 2,304 people developed dementia.
The initial evaluation of study participants was conducted between 2006 and 2010. Participants were followed up until the beginning of this year.
The researchers acknowledged that their observational study was unable to establish the cause and had other limitations related to the way the data was captured. The analysis was published in the British Journal of Ophthalmology.
Another recent study it has also contributed to the understanding between the eye-brain connection in Alzheimer’s disease. These researchers found deposits of amyloid plaques in the retina, the thin layer of tissue inside the eye that allows vision. These protein deposits are normally found in the brain and are associated with Alzheimer’s disease.
The discovery may eventually help make early-stage Alzheimer’s detection easier due to the less invasive and less expensive nature of retinal imaging compared to brain scans.