Smell test may detect early Alzheimer's: study

A smell test that ascertains how well people can identify odours may help predict cognitive decline and detect early-stage Alzheimer's disease, new research suggests.
Two new studies suggest that the University of Pennsylvania Smell Identification Test (UPSIT) may offer a practical, low-cost alternative to other tests.
In one study, researchers administered UPSIT to 397 older adults (average age of 80 years) without dementia from a multi-ethnic population in northern Manhattan.
Each of the participants also had a Magnetic resonance imaging (MRI) scan to measure the thickness of the entorhinal cortex - the first area of the brain to be affected by Alzheimer's disease.

Four years later, 50 participants (12.6 per cent) had developed dementia and nearly 20 per cent had signs of cognitive decline.
The researchers found that low UPSIT scores, but not entorhinal cortical thickness, were significantly associated with dementia and Alzheimer's disease. Low UPSIT scores indicate decreased ability to correctly identify odours.

Low UPSIT scores, but not entorhinal cortical thickness, also predicted cognitive decline, although entorhinal cortical thickness was significantly associated with UPSIT scores in those who transitioned to dementia.
"Our research showed that odour identification impairment and, to a lesser degree, entorhinal cortical thickness were predictors of the transition to dementia," said Seonjoo Lee, assistant professor at Columbia University Medical Center (CUMC).

"These findings support odour identification as an early predictor and suggest that impairment in odour identification may precede thinning in the entorhinal cortex in the early clinical stage of Alzheimer's disease," said Lee.
In another study, researchers evaluated the usefulness of UPSIT and tests that measure the amount of amyloid in the brain (in higher amounts, the protein forms plaques in the brains of those with Alzheimer's disease) in predicting memory decline.
The researchers administered UPSIT and performed either beta amyloid PET scanning or analysis of cerebrospinal fluid in 84 older adults (median age of 71 years).
Of these, 58 participants had mild cognitive impairment. The researchers followed the participants for at least six months.

At follow-up, 67 per cent of the participants had signs of memory decline. Testing positive for amyloid with either method, but not UPSIT score, predicted cognitive decline.
However, participants with a score of less than 35 were more than three times as likely to have memory decline as those with higher UPSIT scores.
"Our research suggests that both UPSIT score and amyloid status predict memory decline," said William Kreisl, a neurologist at NewYork-Presbyterian Hospital.