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A provocative new report suggests a low-cost, non-invasive testing protocol may identify older individuals at increased risk of Alzheimer’s disease. There is a new discovery by the investigators from Massachusetts General Hospital (MGH) on testing individuals’ ability to recognize, remember and distinguish between odors provided similar recommendations as genetic, imaging, and more detailed memory tests.
The testing of both olfactory and cognitive abilities as a means to designate candidates for treatments designed to halt or slow Alzheimer’s symptom development has been shown on the report and published online in Annals of Neurology.
Mark Albers, M.D., Ph.D., of the MGH Department of Neurology mentions an increasing evidence of neurodegeneration behind Alzheimer’s disease starts at least 10 years before the onset of memory symptoms. Development of an affordable, accessible and non-invasive means to identifying healthy individuals who are at risk is a critical step to developing therapies that slow down or halt Alzheimer’s disease progression.
Other studies have associated deficits in odor identification with established Alzheimer’s disease biomarkers and with greater rates of cognitive decline. The most commonly used test of olfactory ability – University of Pennsylvania Smell Identification Test – has a few limitations and does not consider the great variation in olfactory ability among healthy individuals.
In the research the MGH team used a battery of four tests to addresses both olfactory and cognitive functions:
• In the OPID (Odor Percept IDentification)-10 test, participants are presented with a battery of 10 odors — menthol, clove, leather, strawberry, lilac, pineapple, smoke, soap, grape, or lemon. After experiencing each odor for two seconds, they are asked whether the scent is familiar and then asked to choose among four words — from the names listed above — for the one that best describes the odor.
• Participants then complete the Odor Awareness Scale (OAS), a previously validated questionnaire that assesses their overall attention to environmental odors and how they are affected emotionally and behaviorally by scents.
• The OPID-20 test includes the 10 odors previously presented and an additional 10 — banana, garlic, cherry, baby powder, grass, fruit punch, peach, chocolate, dirt, and orange. Participants are first asked whether a presented odor was included in the OPID-10 test and then asked which word best describes the odor. Their ability to remember odors from the first test determines their POEM (Percepts of Odor Episodic Memory) score.
• In the Odor Discrimination (OD) test, participants are presented with two consecutive odors and asked whether they were different or the same, a process that is repeated 12 times with different paired scents.
There are 183 participants, most of whom were enrolled in ongoing studies at MGH- based Massachusetts Alzheimer’s Disease Research Center.
During the olfactory testing, 70 were cognitively normal, 74 tested normal on cognitive tests but were personally concerned about their cognitive abilities, 29 had mild cognitive impairment, and 10 had been diagnosed with possible or probable Alzheimer’s disease.
Results of the OPID-20 test significantly differentiated among four groups of participants, and those results correlated with the thinning of two brain regions – the hippocampus and the entorhinal cortex – previously associated with Alzheimer’s risk.
Participants’ ability to remember a previously presented aroma, as reflected in the POEM score, also showed significant differences between the two cognitively normal groups and participants with Alzheimer’s disease, whose results were no better than chance.
Because the ability of normal individuals to recognize and discriminate between odors can vary by as much as 40 times, the POEM scores of the two cognitively normal groups were compared with what would have been predicted based on their ability to identify and differentiate between odors, as reflected in the OAS and OD tests.
That comparison determined whether each individual was a good or poor POEM performer, and poor POEM performers were more likely to have the variant of the APOE gene associated with increased Alzheimer’s risk. While results of an annual test of short-term memory improved year-to-year for the good POEM performers, no such improvement was seen among the poor performers, who also showed thinning of the entorhinal cortex.
A larger-scale study is still in the progress to validate these results – early diagnosis and intervention are likely to produce the most effective therapeutic strategy for Alzheimer’s disease, preventing onset or progression of symptoms.
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Category(s):Cognitive Problems Amnesia / Dementia
Source material from Brain Blogger
