Smell and Eye Tests May Soon Detect Dementia

eyetestGrowing research evidence suggests that decreased ability to correctly identify odors is a predictor of cognitive decline and an early clinical feature of Alzheimer’s disease. The potential of using smell and eye tests to detect memory decline at an early stage was bolstered by new evidence, presented at the Alzheimer’s Association International Conference (AAIC) last month.

In particular, a recent Columbia University Medical Center study examined 397 people from a multiethnic community in North Manhattan. Researchers evaluated changes in odor identification as an early predictor of cognitive decline, and compared it to two established biological markers for cognitive decline and dementia – brain amyloid PET imaging and thickness of the brain’s cortex in areas important to memory. Those who scored lower on the odor identification testing were significantly associated with the transition to dementia and Alzheimer’s disease.

Another study, reported at AAIC 2016, found a strong association between thinning nerve layers in the retina of the eye and poor cognition, suggesting the potential of retinal imaging as part of early Alzheimer’s testing. Researchers used polarization imaging to look at the retina of both people with Alzheimer’s and canines, and found retinal amyloid deposits. Cognitive dysfunction syndrome is a naturally occurring condition in canines with similar changes in the brain to those in humans with Alzheimer’s.

Polarization imaging is noninvasive and can detect amyloid deposits in the retina prior to disease symptoms. That means it can be an essential tool for detecting or even preventing Alzheimer’s and other dementias.

Currently, the presence of amyloid in the brain is measured using PET brain scans that are expensive, not generally covered by insurance, and not always locally available. After death, evidence of beta amyloid in the brain in association with a history of dementia is the gold standard for diagnosis of Alzheimer’s disease. As an inexpensive alternative to PET scans, polarized light may detect protein deposits in the retina. This method requires no dyes or invasive testing.

While more research is needed, because these methods are much less expensive and easier to administer than PET imaging or lumbar puncture, smell and eye testing may prove to be a useful tool in helping physicians counsel patients who are concerned about their risk of memory loss.

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