The smell of Alzheimer’s

Credit: Nick Youngson

Diagnosis is one of the trickiest steps in disease management for many diseases, ranging from some types of cancer to rare diseases or neurodegenerative disorders, like Alzheimer’s for instance. Even though we have been hearing long about the disease, to date the only reliable diagnosis comes from a postmortem brain analysis and the finding of amyloid plaques in it. One of the biggest challenges of Alzheimer’s research is to come up with a reliable screening/diagnostic method that would help treat the early symptoms and aim to stop the progression of the disease.
Recently a Canadian team of researchers has reported 1 that smell problems could be an early diagnostic sign of the disease. The concept, however, is not new: a relationship between memory loss and smell problems has been known for long. This is not such a surprising link since the olfactory bulb (behind the sense of smell) and the entorhinal cortex (identification of doors) are among the brain regions that are earlier affected by the disease.

Just a simple gesture could help Alzheimer’s diagnosis

To prove their point, the researchers recruited around 300 patients with familial risk of Alzheimer’s and tested their odour discerning ability by means of sniff tests. Of those 300, 100 agreed to get their spinal fluid regularly tested for Alzheimer’s proteins.

When looking the results from the smell tests and the findings on spinal fluid, the researchers found a correlation between the smell identifying issues and the amount of Alzheimer’s related proteins in the spinal fluid.

However, it is important to note that correlation is not causation. That means, that even when a positive relationship between the 2 factors could be found, there is no clear explanation or mechanism known for it and therefore the extent of the diagnostic potential of smell tests relative.

It is definitely too soon to start thinking about a single smell test for Alzheimer’s diagnosis, but it is a finding that brings hope to the completion of a diagnostic battery test for Alzheimer’s.

References

  1. Marie-Elyse Lafaille-Magnan et al (2017) Odor identification as a biomarker of preclinical AD in older adults at risk Neurology doi: 10. 1212/ WNL. 0000000000004159

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