Alzheimer's & Mental Health News for Senior Citizens

Alzheimer's & Mental Health News

Failing smell test signals cognitive impairment, Alzheimer’s for elderly

One of several studies linking poor sense of smell with dementia

Nov. 16, 2015 - The latest study to link a poor sense of smell with Alzheimer’s disease included a group of elderly patients with an average age of 79.5 years. Those who did the worst on the smell test were more likely to have amnestic mild cognitive impairment - predominantly memory loss - and a progression to Alzheimer disease.

Previous research has suggested associations of loss of a sense of smell with cognitive decline, mild cognitive impairment (MCI) or Alzheimer disease (AD) dementia.

Rosebud O. Roberts, M.B., Ch.B., of the Mayo Clinic, Rochester, Minn., and coauthors sought to replicate previous findings in a larger study, according to an article published online by JAMA Neurology.


Participants’ sense of smell was assessed through a test with six food-related and six nonfood-related smells (banana, chocolate, cinnamon, gasoline, lemon, onion, paint thinner, pineapple, rose, soap, smoke and turpentine).

The study in Minnesota included 1,430 cognitively normal individuals, with an average age of 79.5 years, who were nearly evenly divided between men (49.4 percent) and women.

Over an average of 3.5 years of follow-up, the authors identified 250 incident (new) cases of MCI among the 1,430 participants.

The authors report an association between a decreasing ability to identify smells, as measured by a decrease in the number of correct answers in the smell test score, and an increased risk of amnestic MCI (aMCI).

There appeared to be no association between a decreased sense of smell score and nonamnestic MCI (naMCI), which can affect other thinking skills.

The authors also reported 64 dementia cases among 221 individuals with prevalent MCI. A decrease in the frequency of any or AD dementia was associated with increasing scores on the smell test. The worst smell test score categories were associated with progression from aMCI to AD dementia.

Potential explanations for the current findings involve neurodegenerative changes in the olfactory bulb and brain regions that involve smell.

 “Clinical implications of our findings are that odor identification tests may have use for early detection of persons at risk of cognitive outcomes,” the authors conclude.

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