Smell Test Detects Early Alzheimer’s

A sniff test that ascertains how well people can identify odors may prove useful in predicting early-stage Alzheimer’s disease, research shows.

Alzheimer’s disease is incurable and scientists are searching for a way to identify it earlier in hopes of developing effective treatments.  Current tests are only capable of clinically detecting Alzheimer’s disease in the later stages of its development, when significant brain damage has already occurred.

Two new studies suggest that the results of a standardized smell identification test may offer a practical, low-cost alternative to other tests.

In one study, researchers administered the University of Pennsylvania Smell Identification Test (UPSIT) to 397 older adults (average age of 80 years) without dementia. Each were also given an 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 percent) had developed dementia, and nearly 20 percent had signs of cognitive decline.

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 odors.) Low testing scores, but not cortical thickness, also predicted cognitive decline, although both measures were associated with those who developed dementia.

In another study, the researchers administered the odor test along with 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 percent of the participants had signs of memory decline. Testing positive for amyloid with either method, but not UPSIT score, predicted cognitive decline. However, those who did worse on the smell test were more than three times as likely to have memory decline as those with higher scores.

The studies, conducted by researchers from Columbia University, New York State Psychiatric Institute, and NewYork-Presbyterian, were presented at the Alzheimer’s Association’s International Conference in Toronto.