A new study revealed that the decline in a person's olfactory sense may be an indicator of mild cognitive impairment, Lewy body, vascular dementia or Alzheimer's disease.

Researchers from the Mayo Clinic examined 1,630 respondents who were enrolled in the Mayo Clinic Study of Aging in 2004 to 2010. The respondents, with an average age of 79 years old, were clinically evaluated for every 15 months until 2014.

The participants of the study were under three different conditions: normal cognition, mild cognitive impairment (amnestic or nonamnestic), and dementia. To assess their olfactory sense, the researchers administered the Brief Smell Identification Test (B-SIT) on these participants. The B-SIT included six food-related scents such as chocolate, banana, cinnamon, pineapple, lemon, and onion, as well as six nonfood-related scents such as gasoline, paint thinner, soap, turpentine and smoke.

In a study issued in the journal JAMA Neurology, researchers found that participants who had the worst smell test scores were 2.2 times more likely to begin having mild memory problems. If they were already classified with mild cognitive impairment, they were more likely to develop Alzheimer's disease.

After an average of 3.5 years of medical follow-up, 250 participants developed mild cognitive impairment, while 64 of 221 people with the most severe cognitive impairment ended up having dementia, the study said.

Researchers said that as the inability to identify scents increased, so did the likelihood of developing Alzheimer's and increased memory problems. However, the association does not prove a cause-and-effect relationship, they said.

Researchers also did not find any link between decreased olfactory function and the thinking problems related to mild cognitive impairment.

Rosebud Roberts, lead author of the study, said that their findings suggest that a smell test can help identify if people with normal cognition may someday acquire Alzheimer's and other neurodegenerative disorders.

"Physicians need to recognize that this may be a possible screening tool that can be used in the clinic," said Roberts.

James Hendrix of the Alzheimer's Association said that a smell test could be an early indicator for diseases that affect the brain, and that a follow-up will greatly determine what the disease is. However, Hendrix said that it is still too early to incorporate the smell test as a diagnostic tool.

"Our ability to sense smell doesn't just reside in our nose, there are receptors that are activated in our brains," he said. "We need to have a healthy brain to fully smell the world around us."

Photo: Martin Cathrae | Flickr

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