Alzheimer’s first signs may appear in your eyes- edited by Aishee Biswas

Scientists have been investigating the potential of the eye as a diagnostic tool for Alzheimer’s disease, enabling early detection before symptoms manifest. The disease significantly progresses before memory and behavior are impacted. According to a preventive neurologist specializing in Alzheimer's disease at the Institute for Neurodegenerative Diseases, "Alzheimer’s disease initiates in the brain many years before the onset of memory loss." Early detection of the disease could allow people to make healthy lifestyle choices and manage modifiable risk factors such as high blood pressure, high cholesterol, and diabetes.

 

The scientists examined the eyes and brain tissue of 86 deceased patients who had previously been diagnosed with either Alzheimer’s disease or mild cognitive impairment. The researchers additionally compared samples from individuals with normal cognitive function, early-stage symptoms, and late-stage Alzheimer’s. In patients with mild cognitive impairment and Alzheimer’s disease, the researchers discovered an excess amount of amyloid beta 42 in their retinas. This protein forms the "plaques" that accumulate in the brains of individuals with Alzheimer’s.

 

The Alzheimer's Association reports that over six million Americans currently suffer from Alzheimer's disease.

 

A recent study aimed to determine how early signs of cognitive decline can be detected by examining donated tissue from the retina and brains of 86 people with varying degrees of mental decline. The senior author of the study, Maya Koronyo-Hamaoui, who is a professor of neurosurgery and biomedical sciences at Cedars-Sinai in Los Angeles, stated that their research is the first to provide in-depth analyses of the protein profiles and the molecular, cellular, and structural effects of Alzheimer's disease in the human retina and how they correspond to changes in the brain and cognitive function. Koronyo-Hamaoui further explained that the changes observed in the retina correlated with changes in the entorhinal and temporal cortices of the brain, which are important for memory, navigation, and time perception. Over a period of 14 years, investigators collected retinal and brain tissue samples from the largest group of retinal samples ever studied, including individuals with Alzheimer's disease and mild cognitive impairment. The study found significant increases in beta-amyloid, a key marker of Alzheimer's disease, in people with both Alzheimer's and early cognitive decline. In addition, microglial cells, responsible for repairing and maintaining other cells, including clearing beta-amyloid from the brain and retina, declined by 80% in those with cognitive issues. Furthermore, the study found that diets such as the Mediterranean and MIND diets can reduce signs of Alzheimer's in brain tissue.

It was stated that markers of inflammation were also discovered, which could be an equally crucial indicator of disease progression. The study found that these new eye tests could be beneficial in early detection since the findings were evident in individuals with no or minimal cognitive symptoms. The researchers discovered a higher number of immune cells surrounding amyloid beta plaques and other cells that cause inflammation, cell, and tissue death. The study also revealed that tissue atrophy and inflammation in cells on the far periphery of the retina were the most accurate predictors of cognitive status. These findings could potentially lead to the development of imaging techniques that allow for the early and accurate diagnosis of Alzheimer's disease and non-invasive monitoring of its progression by examining the eye.