This may be the earliest sign of Alzheimer’s disease, according to a new study
A new study published this week reveals a possible early predictor of later cognitive decline.
Each year, more than 3 million Americans get an Alzheimer’s disease diagnosis. The condition gradually impairs memory and cognitive function.
There is currently no single diagnostic test that can conclusively identify a patient with Alzheimer’s disease, and the most recent medications simply slow—rather than stopping—progression.
Detecting the illness during its initial phases could be a potential strategy to halt its advancement.
To learn more, researchers at Cedars-Sinai conducted a comprehensive investigation on the changes occurring in the retina – the layer of tissue at the back of the eye that serves as the source of visual information – and their association with brain and cognitive changes in individuals affected by Alzheimer’s disease.
According to senior author Maya Koronyo-Hamaoui, this is the first study “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 with changes in the brain and cognitive function.”
The outcomes of this study could potentially pave the way for the creation of imaging methods that enable the early and precise diagnosis of Alzheimer’s disease and the non-invasive tracking of its progression through examination of the eye, according to the author.
Yosef Koronyo, MSc, research associate in the Department of Neurosurgery at Cedars-Sinai and the primary author of the research, explained that the retina, which is an outgrowth of the brain during development, presents an exceptional opportunity for cost-effective and non-invasive monitoring of the central nervous system.
He further stated that through their collaboration, they uncovered the presence of extremely toxic proteins in the retinas of individuals afflicted with Alzheimer’s disease and mild cognitive impairment, leading to significant cellular degeneration.
Researchers looked at samples of retinal and brain tissue from 86 people who gave them over a 14-year period. This is the largest group of retinal samples from people with Alzheimer’s disease and mild cognitive impairment that has been studied so far.
Donors with normal cognitive function, early-stage Alzheimer’s disease moderate cognitive impairment, and late-stage Alzheimer’s disease dementia were all studied and compared.
Researchers measured and mapped signs of inflammation and functional cell loss in the retinas of these individuals, as well as evaluated proteins in the retinas and brains.
The following is what researchers observed in the retinas of individuals diagnosed with Alzheimer’s disease and mild cognitive impairment:
- An excessive amount of amyloid beta 42, a protein that collects together to form plaques in the brains of people with Alzheimer’s disease and interferes with cognitive function.
- Amyloid beta protein buildup in ganglion cells, the cells that connect the retina’s visual information to the optic nerve
- Microglia, a kind of immune cell, and astrocytes in greater numbers are densely encircling amyloid beta plaques.
- Microglia, the cells responsible for removing amyloid beta proteins from the brain and retina, are reduced by as much as 80%.
- Certain biological processes and chemicals that cause inflammation, cell and tissue death
These changes in the retina were linked to changes in parts of the brain called the entorhinal and temporal cortices, according to Koronyo. These parts of the brain are important for memory, navigation, and being able to tell time.
Changes in the retina were also linked to the pathological stage of Alzheimer’s disease (called the Braak stage) and how well a patient could think. And they were found in people who seemed to have normal or only mild cognitive problems. This suggests that they could be an early sign of later cognitive decline.
Keith L. Black, MD, the Ruth and Lawrence Harvey Chair in Neuroscience and the Chair of the Department of Neurosurgery at Cedars-Sinai, and one of the study’s co-authors, stated that the outcomes provide a more profound insight into the impact of Alzheimer’s disease on the retina.
He added that as these changes align with those seen in the brain and can be detected during the earliest stages of cognitive decline, they could pave the way for new diagnostic approaches for Alzheimer’s disease and an avenue for assessing novel treatment methods.
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