In a study from the University of Chicago, scientists found that older people who could not identify at least four out of five common odors were more than twice as likely as those with a normal sense of smell to develop dementia within five years.
Although 78% of those tested were normal – correctly identifying at least four out of five scents – about 14% could name just three out of five, 5% could identify only two scents, 2% could name just one, and one percent of the study subjects were not able to identify a single smell.
In the study, the team examined nearly 3,000 adults aged 57 to 85.
Five years after the initial test, almost all of the study subjects who were unable to name a single scent had been diagnosed with dementia.
Nearly 80 percent of those who provided only one or two correct answers also had dementia, with a dose-dependent relationship between the degree of smell loss and the incidence of dementia.
These results show that the sense of smell is closely connected with brain function and health.
The researchers think smell ability specifically, but also sensory function more broadly may be an important early sign, marking people at greater risk for dementia.
They suggest loss of the sense of smell is a strong signal that something has gone wrong and significant damage has been done.
This simple smell test could provide a quick and inexpensive way to identify those who are already at high risk.
A previous study found olfactory dysfunction was associated with an increased risk of death within five years.
In that study, loss of the sense of smell was a better predictor of death than a diagnosis of heart failure, cancer, or lung disease.
The team says olfactory deficits are often an early sign of Parkinson’s or Alzheimer’s disease. They get worse with disease progression.
Losing the ability to smell can have a substantial impact on lifestyle and well-being.
People who can’t smell face everyday problems such as knowing whether food is spoiled, detecting smoke during a fire, or assessing the need for a shower after a workout.
Being unable to smell is closely associated with depression as people don’t get as much pleasure in life.
If you care about dementia, please read studies about how the Mediterranean diet could protect your brain health, and Vitamin B supplements could help reduce dementia risk.
For more information about brain health, please see recent studies about Vitamin D deficiency linked to higher dementia risk, and these antioxidants could help reduce dementia risk.
The study was conducted by Jayant M. Pinto et al and published in the Journal of the American Geriatrics Society.
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