Can a smell test predict Alzheimer’s? According to research conducted at Columbia University Medical Center (CUMC), New York State Psychiatric Institute, and NewYork-Presbyterian, it just might. When aging people take an odour identification test, their inability to detect odours may correlate to a cognitive decline and early-stage Alzheimer’s disease.
The two studies that point to this idea were presented at the Alzheimer’s Association’s International Conference in Toronto, Canada. These studies show that the University of Pennsylvania Smell Identification Test, also known as UPSIT, may work as a practical and affordable alternative to other Alzheimer’s early-detection tests.
In one of the studies, UPSIT was administered to 397 older adults who had an average age of 80 years. The 397 people were from a multiethnic population in northern Manhattan, and none of them had dementia at the time of the experiment. Each participant was given an MRI scan and the thickness of the entorhinal cortex was measured. This is the area of the brain that is first affected when a person gets Alzheimer’s disease.
The researchers checked in with the participants four years later, at which time 50 participants had developed dementia. This made up 12.6 per cent of the participants. Almost 20 per cent of the participants showed signs of cognitive decline.
The study found that low UPSIT scores, an indication of a decreased ability to identify odours correctly, had a significant association with dementia and Alzheimer’s disease. Entorhinal cortical thickness, however, was not associated with dementia or Alzheimer’s disease. Cognitive decline was also predicted by low UPSIT scores, but not entorhinal cortical thickness. Entorhinal cortical thickness was, however, significantly associated with UPSIT score of participants who transitioned to dementia.
The study ultimately showed that impairment in odour identification, and to a lesser degree, entorhinal cortical thickness, can help predict the transition to dementia. The findings suggest that perhaps odour identification impairment precedes thinning of the entorhinal cortex in those who are in the early clinical stage of Alzheimer’s.
In the second study, researchers at Columbia University Medical Center (CUMC) assessed how useful UPSIT and tests that measure the level of amyloid in the brain are in predicting memory decline. The reason a test for amyloid was used is because large amounts of this protein can form plaques in the brains of people with Alzheimer’s disease. The participants in this study were 84 older adults with a median age of 71 years. The researchers administered UPSIT to the participants, and also either preformed beta amyloid PET scanning or analysed the cerebrospinal fluid. It was found that 58 of these participants had mild cognitive impairment. The researchers then kept track of these participants for at least six months.
Upon following up with the participants, the researchers found that 67 per cent of the participants had signs of a declining memory. Testing positive for amyloid through either of the two methods predicted cognitive decline. UPSIT scores did not, but participants who had a score of less than 35 were over three times as likely to have declines in memory as those who have higher UPSIT scores. The research ultimately suggests that both UPSIT scores and amyloid states could predict a decline in memory, but further research is needed.
The current methods for finding Alzheimer’s are only able to clinically detect the disease in its later stages of development, at which point significant brain damage has already occurred. If the UPSIT test or analysis of amyloid plaques could be used to predict Alzheimer’s, this would be a huge breakthrough in Alzheimer’s detection.