Can a Special Smell Test Detect Early Alzheimer’s?

Tuesday, July 15, 2014 | 8:56 pm

New research suggests that a decreasing sense of smell might signal the early stages of Alzheimer’s disease.

Two different studies revealed that the decreased ability to identify odors was associated with the loss of brain cell function and progression to Alzheimer’s disease.

“We’re trying to be able to diagnose Alzheimer’s earlier and theoretically deliver drugs to people sooner,” said Matthew Growdon, lead author of one of the studies. “Think about cardiovascular disease as a paradigm; the idea is that we would find a way to control the risk factors.”

The first cranial nerve transmits information from smell receptors in the nose directly to the brain. If brain cells which receive information from the first cranial nerve are damaged by amyloid plaques seen in Alzheimer’s patients, then those people would lose their sense of smell. Brain regions that process odors are particularly vulnerable to Alzheimer’s early in the disease process.

Study participants who had elevated levels of amyloid in their brain had evidence of greater brain cell death and diminished ability to smell, Growdon said. The data took into account the participants’ age, gender, intelligence and brain scans.

Alzheimer’s is the most common form of dementia accounting for 60 percent to 80 percent of dementia cases, according to the Alzheimer’s Association.

The research is to be presented Sunday at the Alzheimer’s Association International Conference in Copenhagen, Denmark. Findings presented at medical meetings are considered preliminary until they are published in a peer-reviewed journal.

For Growdon’s study, the researchers had 215 people from the Boston area who were between the ages of 64 and 88 and were participating in a research project designed to see whether results of brain scans are related to memory changes that occur in healthy older adults.

Participants received brain scans, genetic testing, blood and spinal fluid tests, and PET scans to detect amyloid plaques in the temporal lobe, an area important for memory. They also took a smell identification test known as the University of Pennsylvania Smell Identification Test (UPSIT) and a comprehensive set of tests to measure thinking skills.

“This research shows that the UPSIT/odor identification testing could theoretically be an affordable and quick screening test that could be followed up by more expensive, involved and accurate tests such as PET scans or cerebral spinal fluid studies,” Growdon said.

The second study, led by Dr. Davangere Devanand, a professor of psychiatry and neurology at Columbia University Medical Center in New York City, found that among 757 participants, lower scores on the UPSIT smell test were associated with the transition to dementia and Alzheimer’s disease.

Authors of both studies cautioned that their results were simply a snapshot in time, and larger studies that follow people over a longer period of time would be necessary to confirm the findings. Furthermore, there are many causes for loss of smell such as seasonal allergies, upper respiratory tract infections or trauma that is not associated with Alzheimer’s.

While there is great potential for the test, the important thing to remember is if you are having memory problems, then go see your doctor.

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