- Several systemic conditions — conditions that affect the entire body — are modifiable risk factors for dementia.
- Some types of vision impairment may be early indicators of dementia.
- When systemic conditions combine with vision impairment, the risk of dementia is significantly higher.
There are currently no effective treatments to stop the progression of dementia. Therefore, it is important to identify risk factors, especially those that are modifiable, to aid in the control and eventual prevention of this pandemic.
A recent study, which appears in the British Journal of Ophthalmology, examines ophthalmic and systemic conditions and their relationship to dementia.
Leading risk factors for dementia
Numerous studies have identified that systemic conditions, such as obesity, depression, hypertension, and diabetes, are leading risk factors for dementia.
On the other hand, studies investigating a possible relationship between vision impairment and dementia or cognitive impairment are inconsistent and limited by small sample sizes.
Ophthalmic and systemic conditions often occur simultaneously, as they are all linked to increasing age. However, it is unclear whether these ophthalmic conditions are independently associated with a higher risk of dementia.
The authors of the recent study analyzed data from the UK Biobank to determine whether ophthalmic conditions alone — in the absence of other high risk systemic conditions — are indicators of a higher incidence of dementia.
For the study, researchers assessed 12,364 adults aged 55–73 years between 2005 and 2010 and then followed them up for 11 years until 2021. During this time, they recorded 2,304 cases of all-cause dementia along with 945 cases of Alzheimer’s disease and 513 cases of vascular dementia.
The scientists asked these participants whether a doctor had told them during the study period that they had certain common medical conditions. These conditions included heart disease, stroke, high blood pressure, depression, and diabetes.
Study results
Analysis of the data showed that stroke only, heart disease only, diabetes only, hypertension only, and depression only were independently linked to an increased risk of dementia.
In combination with any of these conditions, age-related macular degeneration was also associated with an increased risk of dementia.
This combination risk was larger than for those with macular degeneration only or just the systemic condition.
Compared with participants who did not have an ophthalmic condition at the start of the study, the risk of dementia was 26% greater in those who developed age-related macular degeneration during the study period.
Participants with cataracts showed an 11% increase in risk, and those with diabetes-related eye disease were 61% more likely to experience dementia.
Glaucoma was not associated with an increased risk of Alzheimer’s disease or all-cause dementia. However, the condition did indicate a higher risk of vascular dementia. The authors noted that when glaucoma co-occurred with stroke, heart disease, diabetes, hypertension, or depression, the risk for all-cause dementia increased significantly.
Relationship remains unclear
The reason for an apparent association between ophthalmic conditions and dementia is unknown, but the authors list several possibilities.
Ophthalmic conditions often co-exist with well-known systemic risk factors of dementia. They are also often present in older individuals, those who smoke and are less physically active, and those with low levels of education.
Most notably, vision impairment may be one of the first manifestations of dementia. Reduced stimulation of visual sensory pathways may lead to an acceleration of its progression.
Dr. Richard Rosen, a vitreoretinal surgeon at Mount Sinai Medical Center in New York City and vice chair and director of ophthalmology research, told Medical News Today that this study reinforces the fact that healthcare professionals need to be on the lookout for these risk factors.
“People that do have these risk factors need to be monitored,” said Dr. Rosen. He stressed that there are new approaches that may be able to control the progression of dementia and perhaps eventually prevent the disease.
“More research is needed in diverse populations to compare eye conditions and dementia risk,” said Claire Sexton, DPhil, the Alzheimer’s Association’s director of scientific programs and outreach, in an interview with MNT.
She also stressed that more research is necessary to determine whether correcting vision loss can reduce the risk of cognitive decline.
“Bottom line for individuals is: If you are experiencing vision loss, it’s important to consult an eye doctor to explore possibilities of sight correction,” said Sexton.
While the study population was notably large and covered a significant time span, the authors note that this was an observational study only and that it does not indicate causality. They also mention several other limitations.
For instance, the authors explain that many of the ophthalmic conditions were self-reported. Also, some of the reported cases of dementia may have occurred before the eye disease.
The authors conclude that age-related macular degeneration, cataracts, and diabetes-related eye disease, but not glaucoma, are associated with an increased risk of dementia.
People who have both ophthalmic and systemic conditions are at an even higher risk compared with those with an ophthalmic condition only or a systemic condition only.
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