A simple, low-cost odour identification test may prove useful in predicting mental decline as well as help in detecting Alzheimer's disease during its early stages, reveals a study.
The Smell Identification Test (SIT) developed by the University of Pennsylvania in the US, may offer a practical, low-cost alternative to other tests, the researchers said.
A low SIT score indicated decreased ability to correctly identify odours and also predicted mental impairment.
"Our study adds to the growing body of evidence demonstrating the potential value of odour identification testing in the detection of early stage Alzheimer's disease," said D.P. Devanand, Professor at Columbia University Medical Center (CUMC) in New York, US.
The findings showed that the participants who scored less than 35 in SIT were likely to have more than three times memory decline than those with higher scores.
Further, participants whose brain scans showed a thinning in entorhinal cortical -- the brain area that plays a role in memory and the first brain region affected by Alzheimer's -- were more likely to develop Alzheimer's.
"The study 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 CUMC.
"Odour identification testing, which is much less expensive and easier to administer than PET imaging or lumbar puncture, may prove to be a useful tool in helping physicians counsel patients who are concerned about their risk of memory loss," added William Kreisl, Assistant Professor at CUMC.
For the study, the team administered 397 older adults with an average age of 80 years to SIT, without dementia.
Four years later, 50 participants (12.6 per cent) had developed dementia, and nearly 20 per cent had signs of cognitive decline.
In another experiment the researchers evaluated the usefulness of SIT and other tests that measure the amount of amyloid in the brain in higher amounts in predicting memory decline in 84 older adults with a median age of 71 years.
At follow-up, 67 per cent of the participants had signs of memory decline.
The study was presented at the Alzheimer's Association's International Conference in Toronto, Canada, recently.