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Tuesday, February 25, 2020

Can a Sniff Test Rule out Alzheimer’s?

Researchers have discovered that a simple sniff test, when combined with brief cognitive exams, can help predict a low likelihood of developing Alzheimer’s.

Scientists have known for years that the olfactory bulb, responsible for transmitting smell information from the nose to the brain, is one of the first areas of the brain to be affected by Alzheimer’s disease. That’s why people with early-stage Alzheimer’s often lose the ability to distinguish odors before memory symptoms get noticed.

A new study from Columbia University Irving Medical Center has found that performing well on a sniff test can help predict which patients with mild cognitive impairment will develop Alzheimer’s. While clinicians currently use cognitive exams to screen for dementia, patients with mild cognitive impairment often follow up with difficult and costly diagnostic procedures. However, combining a simple cognitive screening with the odor test was highly predictive of which individuals developed Alzheimer’s later on.

"No one has looked previously at whether performing well on both the odor identification test and global cognitive performance tests is better at predicting a low risk of cognitive decline or development of Alzheimer's disease," says D. P. Devanand, MBBS, MD, lead author of the paper, professor of psychiatry at Columbia University Vagelos College of Physicians and Surgeons, and research psychiatrist at the New York State Psychiatric Institute. "If we could accurately identify individuals who are unlikely to experience cognitive decline and Alzheimer's disease, we would reduce the need for unnecessary diagnostic investigation with PET imaging and lumbar puncture, which can be cumbersome and expensive, and improve selection of patients for clinical trials, including possibly prevention trials."

Study Framework

Participants in the study had mild cognitive impairment without dementia. The 749 older adults finished a brief cognitive screening test and a smell identification test of 40 items. Follow-up occurred over a four-year period when they were monitored for a diagnosis of Alzheimer’s or other dementias. During that time, 109 individuals were diagnosed with a dementia, mostly Alzheimer’s.

Take the Smell Test at Home

You can take the complete 40-item Smell Identification Test at home for under $30. Sensonics International offers the test with a scoring key and “norms from nearly 4,000 men and women spanning the entire age range” to provide a comparison basis.

The company notes the test can be self-administered in only 10-15 minutes. The kit itself is made up of four booklets, each with 10 micro-encapsulated (scratch and sniff) odors. This is the authentic test developed at the University of Pennsylvania with funding from the National Institutes of Health. The minimum quantity to order is seven, but at a cost of $26.95 you could share with friends and family. Each kit is guaranteed accurate within six months of manufacturing.

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An overwhelming 96.5% of the participants who performed well on both tests failed to develop dementia during the follow-up period. The findings indicate that older adults into their mid-80s who are unimpaired on the two brief tests are very unlikely to develop dementia.

Currently, Alzheimer’s can only be detected in its later stages of development, when significant damage has already occurred. PET scans to detect beta amyloid plaque buildup in the brain are expensive. Beta amyloid can also be detected in cerebrospinal fluid via a lumbar puncture.

“Using other biomarkers of Alzheimer’s disease to detect the disease at an earlier stage—which have the potential to be lower-cost and non-invasive—could lead to dramatic improvements in early detection and management of the disease,” says Heather Snyder, Ph.D., director of medical and scientific operations at the Alzheimer’s Association.

Smell Test

Researchers have administered smell tests with as little as five odors. In that test of nearly 3,000 adults, participants had to identify the odors of peppermint (easiest), fish, orange, rose and leather (hardest). Five years later, the results found that older adults with “olfactory dysfunction” (those unable to correctly identify at least 4 out of 5 odors at baseline) had double the chance of developing dementia within the five years following the test.

“We think a decline in the ability to smell, specifically, but also sensory function more broadly, may be an important early sign, marking people at greater risk for dementia,” says senior author Jayant M. Pinto, professor of surgery at the University of Chicago. “These results show that the sense of smell is closely connected with brain function and health.”

Predicting memory loss is still an obscure science. The smell test can help predict an individual’s risk of cognitive decline, but unlike other methods, it can’t say whether that loss is from Alzheimer’s or another neurodegenerative disease. Family history and genetic factors may weigh in on the need for further evaluations. Even something like smoking can alter test results.

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