It is known that Alzheimer’s disease originates in the part of the brain that senses smell, before spreading to other areas. The “olfactory vector hypothesis” suggests that there may be an environmental agent that could enter the brain through the nose.
It is known that changes in smell may pre-date cognitive decline. So, the theory is: Could changes in smell be used to predict Alzheimer’s disease?
Researchers at the University of Florida designed a test based on the fact that the left side of the brain processes what we smell from the left nostril and the right side processes smells from the right nostril. The experiment involved elderly people and peanut butter. People in the control (non-Alzheimer’s group) were able to smell the peanut butter from 7 inches away through either nostril. Patients with Alzheimer’s could smell the peanut butter on the right side from 7 inches but could only detect in from 2 inches away on the left side. This was only seen in Alzheimer’s disease but NOT in other causes of dementia.