March 27, 2025
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The ability to discriminate between odors declines with age, a new study finds. Smell tests may be a tool to flag Alzheimer's and other forms of dementia early, when interventions are most beneficial, researchers say.
A smell test developed by researchers could provide an early indication of dementia.
"Early detection of cognitive impairment could help us identify people who are at risk of Alzheimer's disease and intervene years before memory symptoms begin," Dr. Mark Albers, of the Department of Neurology at Massachusetts General Hospital in Boston, said in a news release.
Prior research has established a link between the sense of smell and the speed of brain loss and cognitive decline. But there are a lack of cost-effective, non-invasive olfactory tests that might help identify cognitive decline in early stages — when interventions are most effective. The study published Monday in Scientific Reports tested a new series of non-invasive smell tests that could be done at home, giving people an early indication of cognitive decline.
Nearly 7 million people in the United States have Alzheimer's, and that number is projected to reach nearly 13 million by 2050 if no effective intervention or cure is found, according to the Alzheimer's Association.
For the study, people sniffed labels fixed to cards to check their abilities to identify different odors, distinguish between new odors and those previously smelled, and recognize pairs of smells that were the same or different. The tests were run on 180 people who spoke English or Spanish. The group included people who had normal cognitive function, who self-reported cognitive issues and who had mild cognitive impairment.
The study found that odor identification, memory and discrimination declined with age. The 19 people with mild cognitive impairment scored lower on the tests than the group with normal cognitive function. Whether people spoke English or Spanish had no effect on the results.
"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," Albers said.
Further studies are needed to see if the smell test used in this study can detect cognitive decline over time, according to the researchers.
