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New Smell Test for Alzheimer's Detection

Posted on Nov. 29, 2016, 6 a.m. in Alzheimer's Disease Diagnostics

New screening for Alzheimer's Disease tests patients' ability to distinguish odors

In a non-evasive procedure developed by a research team from Massachusetts General Hospital, patients were tested to recognize and then remember different odors. The ability for patients to recall the odors later on determined if they were at a higher risk of getting Alzheimer's disease. The intriguing results were published in the Annals of Neurology. There is evidence that the cause of this disease can start as early as 10 years before the onset of Alzheimer's symptoms. The new procedure for testing healthy people is a big step for future medication or therapies that could slow or stop the cognitive impairment that Alzheimer's unleashes.

Battery of Four Odor Tests Form Basis of New Screening


The MGH team designed a test program of four requirements to measure people's olfactory (sense of smell):

  • In the first test called OPID (Odor Percept Identification), participants went through odor tests including the odors pineapple, smoke, lemon, soap, grape, leather, strawberry, menthol, lilac, and clove. They had to experience each one for 2 seconds and then had to match the odor with the one of the 10 listed above.
  • The second test called OAS (Odor Awareness Scale), involved completing a questionnaire which assessed if the odors triggered any memories.
  • The third test (OPID-20) included more odor testing including garlic, baby powder, cherry, banana, fruit punch, grass, orange, chocolate, peach, and dirt. The participants were asked if any of the odors matched any from the first test, and to give the best word describing each odor.
  • In the final test called OD (Odor Discrimination), participants are tested with two odors and then asked if they are the same or different. This process is repeated 12 times with various paired scents.

In total the study recruited 183 participants of which:

  • 70 were already cognitively healthy
  • 74 were cognitively normal in the tests
  • 29 already had mild cognitive impairment
  • 10 were diagnosed with probable Alzheimer's

Results of the third test (OPID-20) showed those participants who had cognitive impairment or probable Alzheimer's also had difficulty remembering the odors from the first test. This correlates with studies showing that people with an Alzheimer's risk had thinning of the brain, in particular, the hippocampus and entorhinal cortex. These people were also more likely to have the APOE gene which is associated with Alzheimer's disease. Annual tests were conducted with all participants with the poor performers in brain scans showing a thinning of the entorhinal cortex.

New Hope for Preventing Alzheimer's Disease


It is already established that the brain's ability to process information is affected by Alzheimer's. Many studies have been documented that conclude a decline in the sense of odor identification in patients with Alzheimer's disease. However, these studies do not take into account the olfactory (sense of smell) among healthy people. The new screening test developed by the MGH team changes everything.

The researchers are continuing to recruit participants for further studies in order to validate the original results. Preventing the onset or progression of Alzheimer's is the goal of this research area as well as developing new therapeutic methods for tackling dementia. If this new screening test for Alzheimer's holds up, it could be the best method for identifying individuals for a host of new therapies that could prevent the debilitating symptoms of this terrible disease.

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Episodic memory of odors stratifies Alzheimer biomarkers in normal elderly, Mark Albers et al., Annals of Neurology, doi: 10.1002/ana.24792, published 1 October 2016

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