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Decline in Sense of Smell is Early Warning Sign for Dementia Risk

Updated on November 16, 2016
janderson99 profile image

Dr. John uses skills in Biochemistry, Physiology (PhD) to review topics on mental health, depression, sleep, stress, setting positive goals

A decline in the sense of smell has been linked with the onset Alzheimer's Disease and dementia.

People with the worst symptoms of these diseases, often show severe loss of olfactory functions.

Various researchers have also found evidence that the loss of smell may be associated with the progression of patients with mild cognitive impairment to dementia.

Though more definitive studies are needed to confirm these findings, they suggest that simple tests for loss of smell could be an effective tool for wide scale screening of people for risks of developing dementia and Alzheimer's disease.

This article reviews current research and outlines how such simple tests could be conducted.

Major changes in the brain associated with Alzheimer's disease have been linked with a decline in the sense of smell.
Major changes in the brain associated with Alzheimer's disease have been linked with a decline in the sense of smell. | Source
A decline in olfactory function may be an early warning sign of the onset of Alzheimer's disease
A decline in olfactory function may be an early warning sign of the onset of Alzheimer's disease | Source

Link between Decline in Sense of Smell and Dementia / Alzheimer's Disease

A major review of this topic concluded that although there was some evidence for a correlation between decreases in the sense of smell and the onset of and Alzheimer's Disease there was a lack of definitive research. The wide variability in the type of olfactory identification test prevented proper analysis.

In one small study, 57 outpatients with late onset mild to moderate Alzheimer's Disease and 24 elderly controls were assessed for cognitive function and olfactory function.

The study found that:

► The group with had lower olfactory scores than the control group.

► The Alzheimer's Disease patients with the worst loss smell function showed more pronounced loss of cognition and higher levels of symptomatic illness.

► There was evidence of an association between the loss of olfactory function and the severity of Alzheimer's Disease functions.

Another study suggested that people aged from 41-85 years old who had lost their sense of smell had about a 50 percent risk of developing Alzheimer's disease later in life. However several other studies were inconclusive.

These studies suggested that the decline in the sense of smell may be an early warning sign of the onset of dementia and Alzheimer's disease or increase risk of future development of dementia.

Development of a Simple Test for the Impairment of the Sense of Smell

One simple test for loss of smell has been developed that used peanut butter and a metric ruler.

The steps required are:

► About one tablespoon of peanut butter was placed in a tiny jar with a lid.

► The patient was asked to close his or her mouth and eyes and to block one nostril.

► The person doing the test then opened the peanut butter jar near the person's open nostril.

► The patient was asked to breath normally.

► The jar was them moved further away along the ruler one centimeter at a time.

► The patient was asked to say when they could no longer smell the peanut butter when breathing normally.

► The test was repeated for the other nostril, with the first nostril closed.

When the tested were repeated for groups of subjects with and without Alzheimer's disease a startling pattern appeared.

Patients in the early stages of the onset of Alzheimer's disease showed major differences in detecting odors with their left and right nostril.

The left nostril showed impaired sense of smell. In terms of the ruler measurements, patients could not smell the peanut butter 10cm closer to the nostril than with the right nostril.

This difference was not shown for the group of subjects with no signs of Alzheimer's disease.

Also about half of the group of patients with showed mild mild cognitive impairment showed loss of smell in the left nostril.

Mild cognitive impairment is regarded as an early warning sign of the risks of developing Alzheimer's disease.

Definitive follow up studies are needed to confirm that the loss of smell in the left nostril may be an early warning sign of the risks of dementia and Alzheimer's disease. the advantage of this test are obvious - it is simple and easy to do with minimal costs and training involved.

© 2013 Dr. John Anderson


Submit a Comment
  • tillsontitan profile image

    Mary Craig 

    5 years ago from New York

    ANYTHING we can do to spot and maybe stop the onset of dementia is always worth investigating. This was very interesting and hopefully research will continue.

    Voted up, useful, and interesting.

  • tobusiness profile image

    Jo Alexis-Hagues 

    5 years ago from Lincolnshire, U.K

    janderson99, forgive my loss of concentration, I think it's time for me to take that test...:) however, I'll just put it down to lack of sleep for now. Once again, great job.

  • tobusiness profile image

    Jo Alexis-Hagues 

    5 years ago from Lincolnshire, U.K

    Lost of the sense of smell is one of the earliest known impairments caused by Alzheimer's. You've done an excellent job in bringing awareness to this important early symptom of this devastating disease.

    Research found that the sense of smell can be restored by removing a plaque-forming protein (amyloid beta) in a mouse model of the disease, the study also confirms that it is this protein which causes the loss. The interesting thing about the new findings is that we now know how and where in the brain the early changes occurs, this have great implication for slowing down the disease and dare we time a possible cure. Voting up all the way and sharing.

  • mperrottet profile image

    Margaret Perrottet 

    5 years ago from San Antonio, FL

    Very interesting article. This research shows lots of promise for early detection of a horribly debilitating disease. Perhaps if detected early medication can slow down the progression of the disease. Voted up, interesting and useful.

  • ChitrangadaSharan profile image

    Chitrangada Sharan 

    5 years ago from New Delhi, India

    This is very important and informative hub regarding warning signs of Dementia. I was just wondering, whether early detection can also help in curing this disease!

    Very useful and well researched! Thanks for sharing!


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