A simple sniff test may be an effective supplementary tool for diagnosing mild cognitive impairment (MCI), a pre-dementia condition which often progresses to Alzheimer’s dementia within a few years, according to a new study by researchers at University of Pennsylvania’s Perelman School of Medicine.
The findings add to the growing body of evidence that our sense of smell declines sharply in the beginning stages of Alzheimer’s disease.
“There’s the exciting possibility here that a decline in the sense of smell can be used to identify people at risk years before they develop dementia,” said principal investigator David R. Roalf, Ph.D., an assistant professor in the department of Psychiatry at Penn.
For the study, the researchers used a simple, commercially available test known as the Sniffin’ Sticks Odor Identification Test, in which people must try to identify 16 different odors. They administered the sniff test and a standard cognitive test (the Montreal Cognitive Assessment) to 728 elderly people.
The participants had already been evaluated by doctors at Penn with an array of neurological methods and had been placed in one of three categories: “healthy older adult,” “mild cognitive impairment,” or “Alzheimer’s dementia.”
Roalf and his team used the results from the cognitive test alone, or combined with the sniff test, to see how well they identified subjects in each category.
The found that the sniff test was highly effective in making accurate diagnoses when combined with the cognitive test.
For example, the cognitive test alone correctly classified only 75 percent of people with MCI, but that figure rose to 87 percent when the sniff test results were added. Combining the two tests also enabled more accurate identification of healthy older adults and those with Alzheimer’s dementia. The sniff-cognitive test combo even boosted accuracy in assigning people to milder or more advanced categories of MCI.
“These results suggest that a simple odor identification test can be a useful supplementary tool for clinically categorizing MCI and Alzheimer’s, and even for identifying people who are at the highest risk of worsening,” Roalf said.
Prompted by previous research that has connected a weakening sense of smell to Alzheimer’s, doctors in a few larger dementia clinics already have begun to use smell tests in their assessments of elderly patients. Part of the reason the practice has not yet become common is that the tests that seem most useful take too long to administer. Roalf and colleagues are now trying to develop a briefer test that is just as accurate as the longer ones.
“We’re hoping to shorten the Sniffin’ Sticks test, which normally takes five to eight minutes, down to three minutes or so, and validate that shorter test’s usefulness in diagnosing MCI and dementia — we think that will encourage more neurology clinics to do this type of screening,” Roalf said.
The research team also plans to investigate whether protein markers of Alzheimer’s, which are present in the olfactory region of the brain before dementia occurs, can be detected in nasal fluid to provide an even earlier warning of the disease process.
Their findings are published in the Journal of Alzheimer’s Disease.