At-Home Smell Test Detects Mild Cognitive Impairment
Key findings
- The previously developed Aromha Brain Health Test (ABHT) assesses odor identification, odor memory, and odor discrimination
- For this study, the ABHT was adapted to be self-administered at home with responses entered online; patients with subjective cognitive concern or mild cognitive impairment were observed by a research assistant via videoconference
- Across participants of all ages, scores on all three parts of the ABHT correlated with cognitive status, and performance was similar among English- and Spanish-speaking participants
- Remote, self-administered smell assessment could accelerate screening for clinical trials and suggest which patients would benefit from additional, more definitive tests
Many brain regions that process olfactory input are damaged early in Alzheimer's disease. In fact, the olfactory bulb and entorhinal cortex are among the first sites of tau pathology. Previous studies suggest olfactory testing can screen for Alzheimer's disease, but the tests have logistical challenges, and their sensitivity is questionable.
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Now, Mark W. Albers, MD, PhD, of the Laboratory of Olfactory Neurotranslation, the McCance Center for Brain Health, and the Department of Neurology at Massachusetts General Hospital; Alefiya Dhilla Albers, PhD, of the Department of Neurology; and colleagues have determined that a remotely administered olfactory test can distinguish between cognitively normal (CN) people, those with subjective cognitive complaints (SCC), and those with mild cognitive impairment (MCI).
"Our goal has been to develop and validate a cost-effective, non-invasive test that can be performed at home, helping to set the stage for advancing research and treatment for Alzheimer's," Dr. Mark Albers says. The team reports the results in Scientific Reports.
Adapting the AROMHA Brain Health Test
The researchers previously developed the Aromha Brain Health Test (ABHT, Aromha, Inc.), which has three parts:
- Odor percept identification test, where participants smell an odor and choose from four provided odor names
- Percept of odor episodic memory test, where participants distinguish between new odors and those presented earlier
- Odor discrimination test, where participants identify pairs of smells as either the same or different
In the new study, the ABHT was updated for remote self-administration. Peel-and-sniff cards were mailed to participants' homes, and they entered responses in a web application they set to English or Spanish. Participants with SCC or MCI administered the test while observed by a research assistant via videoconference. CN participants, representing a wide age spectrum from 20 to 92 years old, could choose to be unobserved.
Participants as old as 88 years in the SCC group and 95 years in the MCI group successfully self-administered the test, with instruction from the research assistant as needed. 95% of MCI participants performed the test at home; the others elected in-person visits.
Test Results Differed by Cognitive Status
127 CN people, 34 with SCC, and 19 with MCI were recruited from 21 U.S. states and Puerto Rico. Across participants of all ages, scores on all three parts of the ABHT correlated with cognitive status. Among those ≥55 years old, every ABHT score was significantly lower in the MCI group than the CN group.
Performance was similar by 71 observed versus 56 unobserved CN participants and by 86 English-speaking versus 41 Spanish-speaking CN participants. Scores on all three parts of the ABHT declined as a function of age, showing they are sensitive to the normal effect of aging on olfaction. As expected, seven anosmic patients performed at chance level.
A Boon to Research
"Our results suggest that olfactory testing could be used in clinical research settings in different languages and among older adults to predict neurodegenerative disease and development of clinical symptoms," Dr. Mark Albers says.
He and his colleagues are exploring whether the ABHT could accelerate screening in asymptomatic or newly symptomatic individuals who would benefit from more definitive subsequent tests, such as blood-based, image-based, or cerebrospinal fluid–based diagnostics. Besides continued research in Alzheimer's disease, they plan to test patients who have Lewy body disease or head trauma, which are known to be capable of causing olfactory impairments.
Dr. Mark Albers and another author, Sean Reineke, are co-founders of Aromha, Inc. and own shares in the company.
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