What the smell test entails
In the study, a “nationally representative sample” of 2,906 men and women aged between 57 and 85 underwent home interviews and completed a simple smell test.
For the “validated five-item test,” they had to identify five odours, one at a time, by sniffing a device similar to a felt-tip pen.
Each time, they were given four choices, from which they had to pick out the correct one.
The five different odours were: peppermint, fish, orange, rose, and leather, with peppermint being the easiest, and leather the hardest, to identify.
After analysing the results, the team found that the participants who had not been able to identify at least four out of the five odours at baseline (the starting point of the comparison) were more than twice as likely to be among those who had developed dementia during the five-year follow-up.
They also found that the lower the number of odours correctly detected at baseline, the higher the chances of dementia being diagnosed during the follow-up period.
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No definitive conclusion
In a linked editorial, Dr. Stephen Thielke – from the Psychiatry and Behavioral Sciences Faculty at the University of Washington in Seattle – notes that this does not mean that “smell testing would be a useful tool for predicting the onset of dementia”.
Prof. Pinto accepted this limitation, noting: “Our test simply marks someone for closer attention.”
What underpins the link?
The reason poor sense of smell is linked to higher rates of death, Parkinson’s disease, and Alzheimer’s disease is unclear, but one possibility is that loss of smell might be an early indication that the condition is present, says Harvard Health.
“Or, perhaps other conditions that affect smell increase the risk of these diseases,” notes the health body.
It adds: “It could also be due to medications taken to treat symptoms of these conditions.”
Source: Daily Express
