Olfactory testing uses extended to Alzheimer’s disease

By Eleanor McDermid, Senior medwireNews Reporter

A simple olfactory test may help to identify people at increased risk of developing Alzheimer’s disease (AD) dementia, suggest findings from a population-based study.

Olfactory dysfunction, already considered a strong risk indicator for Parkinson’s disease, significantly predicted both amnestic mild cognitive impairment (MCI) and further progression to AD dementia among 1430 cognitively normal people aged an average of 79.5 years.

Rosebud Roberts (Mayo Clinic, Rochester, Minnesota, USA) and study co-authors suggest that “odor identification tests may have use for early detection of persons at risk of cognitive outcomes.”

“The B-SIT [Brief Smell Identification Test] is easily administered in the outpatient setting, does not require administration or interpretation by trained personnel, has normative data, is relatively inexpensive, and is noninvasive”, they write in JAMA Neurology.

The test could therefore be an easy way to identify people who may benefit from early intervention to prevent or slow further cognitive decline, they add.

A total of 162 participants of the Mayo Clinic Study of Aging developed amnestic MCI during an average 3.5 years of follow-up, and the risk of this occurring rose in line with poorer baseline olfactory function on the B-SIT, with risk increases of 1.95- and 2.18-fold for participants in the second-bottom and bottom quartiles, respectively, compared with those in the top quartile.

Olfactory function did not predict the risk of non-amnestic MCI; however, only 50 participants were diagnosed with this.

Of the 221 participants with MCI at baseline, 64 progressed to dementia during follow-up. Again, this was strongly aligned with baseline olfactory performance, with participants in the second-bottom and bottom quartiles having respective 3.63- and 5.20-fold increased risks of progression relative to those in the top quartile.

“The strong association for transition from [amnestic] MCI to AD dementia is consistent with an underlying AD pathophysiology”, say the researchers.

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