Alzheimer’s disease (AD), the most common form of dementia, accounts for 60-70% of dementia cases. Diagnosis currently involves many time-consuming tests, which means treatment can be delayed. A new post-mortem study has found significant changes in the retinas of people with mild cognitive impairment or AD before they died. These results could lead to a non-invasive diagnosis of AD by retinal screening.
According to the World Health Organization more than 55 million people worldwide have dementia and some 10 million people are diagnosed each year. In France alone, about 1 million people are affected by this disease.
If a person begins to show signs of cognitive impairment, it is important to seek an early diagnosis. A prompt diagnosis of dementia will give the affected person and their carers time to plan for the future and access treatments which, although they cannot cure the disease, can slow or delay symptoms, and that can help manage symptoms.
Currently, the diagnosis of dementia is based on a number of assessments, including cognitive tests, brain scans, cerebrospinal fluid (CSF) tests, blood tests, psychiatric evaluations, and genetic tests. These assessments can be time-consuming and expensive, which is why much recent research has focused on finding faster, less invasive ways to diagnose dementia. Biomarkers are promising diagnostic tools. Although minimally invasive, most of them involve a blood test or CSF analysis. Recent research has shown that retinal screening can detect signs of AD, making it a potential diagnostic method.
Today, a post-mortem study has revealed that people with cognitive impairment or AD have many retinal changes that are not seen in the retinas of cognitively healthy people. The study, led by researchers at Cedars-Sinai Medical Center, is published in Acta Neuropathologica.
For several years, scientists have been studying how to use imaging technology used in ophthalmology to measure the levels of biomarkers of Alzheimer’s disease in our eyes. The ability to easily detect biological signs of Alzheimer’s disease in the eye is intriguing, as it could allow the disease to be detected non-invasively, at earlier stages, before symptoms appear.
Alzheimer’s disease and changes in the retina
The researchers examined retinal and brain tissue samples taken over 14 years from 86 deceased human donors with Alzheimer’s disease or mild cognitive impairment. These samples were compared with those from cognitively healthy donors. They found molecular, cellular and structural changes in the retina of people with Alzheimer’s disease or mild cognitive impairment. These changes were not seen in the retinas of cognitively healthy people.
Beta-amyloid plaques are common in the brains of people with Alzheimer’s disease, and this study found elevated concentrations of Aβ in the retinas of people with Alzheimer’s disease. Research has shown that Aβ42, a longer molecular form of Aβ, is particularly important in AD pathology. This study confirms that the same cellular, chemical and molecular changes seen in the brains of people with Alzheimer’s disease are evident in the retina. Retinal biomarkers were not evenly distributed in the retina. The density of Aβ42 was much higher in the inner and peripheral retina than in the central retina.
Inflammatory markers in the eyes
The researchers also looked at inflammatory markers in the retinas. Microglia is an immune cell whose action is altered in people with Alzheimer’s disease and other forms of dementia. This study showed that overactivated microglia increase Aβ and Tau, and promote neuroinflammation.
In this study, researchers found that Aβ42 and retinal microgliosis were strongly correlated with cognitive status in both men and women. However, women had higher levels of IBA1+ retinal microgliosis than men. Interestingly, the researchers found higher levels of inflammation in women’s eyes than in men’s. Since women over 65 are more likely to live with Alzheimer’s dementia than men, we need to understand these gender differences and how they contribute to risk.
Retinal examination could be used for diagnosis
Examination of the retina and optic nerve can now diagnose many health problems that are apparently not related to the eye. These include hypertension, diabetes, thyroid disorders and neurodegenerative diseases such as multiple sclerosis (MS).
This study adds to the evidence that retinal examination could also be used to diagnose Alzheimer’s disease.
However, this technology is still in its infancy. Although technological advances have been made to date, allowing an increasingly fine anatomical evaluation of the retina, and correlations with the degenerative changes of Alzheimer’s disease have been described, there is not yet a technology for diagnosing Alzheimer’s disease using a retinal scanner.
A healthy body, a healthy mind
The results of this study suggest that retinal examination may one day provide a simple, non-invasive test for the early detection of Alzheimer’s disease. But that is unlikely to happen soon. In the meantime, we must consider that the most effective tools today are those which allow the detection of Alzheimer’s disease.
Consider that the most effective tools today for slowing the progression of Alzheimer’s disease are the same key factors for achieving and maintaining overall well-being: lifestyle; in other words, don’t wait until you are sick to heal yourself: quit smoking now, quit alcohol and “drugs” now, eat carefully, exercise, sleep well, reduce stress and get regular checkups, vaccinations, and health screenings while you’re “well.”