Some doctors who treat Medicare patients have informally used what they call the “Peanut Butter Test” to gauge a person’s potential Alzheimer’s risk; those who can’t detect the strong aroma of Skippy or Jif are more likely to have early dementia.

Now, they have the backing of scientific research for their observations. Mayo Clinic researchers have determined a decreased sense of smell does indeed appear to be linked to the onset of Alzheimer's, according to an article published in JAMA Neurology.

Autopsy studies have linked a loss of ability to identify odors with the plaques and tangles in regions of the brain tied to memory loss and dementia, Medical News Today reports. 

Knowing this can help doctors identify patients at risk a speed drug treatments, which are most successful when used early on to delay the ravages of Alzheimer’s

Lead researcher Rosebud Roberts assessed the sense of smell of 1,430 cognitively normal individuals, with an average age of 79.5 years, between 2004 and 2010, then tracked them through 2014.

Patients in the study were asked to identify six food-related and six non-food-related smells (banana, chocolate, cinnamon, gasoline, lemon, onion, paint thinner, pineapple, rose, soap, smoke and turpentine).

By the end of the study, 250 of the patients were diagnosed with mild cognitive impairment, a precursor to Alzheimer’s. Roberts’ team found a clear association between a decreasing ability to identify smells and an increased risk for MCI.

"Clinical implications of our findings are that odor identification tests may have use for early detection of persons at risk of cognitive outcomes," the researchers concluded.