"Passing the smell test" may not just be a casual idiom anymore. New research suggests that the decreased ability to identify certain odors may signal early-stage Alzheimer's disease and future cognitive decline.
The test - dubbed the University of Pennsylvania Smell Identification Test - was the focus of two studies presented at the Alzheimer's Association International Conference in Toronto. Both studies were funded by the National Institute on Aging.
In addition to an MRI scan measuring the thickness of the brain region where Alzheimer's typically first strikes, the so-called entorhinal cortex, one of the studies used the smell test on 397 adults in Manhattan, who were 80 years old, on average, and didn't have dementia. Fifty of these people (12.6 percent) had dementia four years after undergoing the initial smell test, while nearly 20 percent showed signs of cognitive decline.
Low smell test scores, or the decreased ability to identify odors correctly, correlated with dementia and Alzheimer's disease and appeared to predict cognitive decline.
"Our research showed that odor identification impairment, and to a lesser degree, entorhinal cortical thickness, were predictors of the transition to dementia," study author Seonjoo Lee, assistant professor of clinical biostatistics (in psychiatry) at Columbia University Medical Center, said in a statement. "These findings support odor identification as an early predictor, and suggest that impairment in odor identification may precede thinning in the entorhinal cortex in the early clinical stage of Alzheimer's disease."
"Our study adds to the growing body of evidence demonstrating the potential value of odor identification testing in the detection of early-stage Alzheimer's disease," senior author of both studies D.P. Devanand, professor of psychiatry at Columbia University Medical Center, said in the same statement.
At present, Alzheimer's disease can only be clinically identified in its later stages, after the brain is severely damaged. Approximately 5.4 million Americans have Alzheimer's, according to the Alzheimer's Association.