Your Ability To Smell 5 Scents Could Reveal Your Dementia Risk As You Age

Though some early signs of dementia, like memory loss and finding it hard to concentrate, are relatively well-known, some symptoms are less commonly understood. 

I didn’t know, for instance, that struggles when taking the stairs can suggest very early dementia development. So, too, can difficulty driving, frailty, and developing issues with grocery shopping or brushing your teeth.

We also know that conditions like Alzheimer’s disease might affect your sense of tasteand smell years before diagnosis. 

And according to a 2017 paper, your ability to smell five strong scents could be a good guide for checking dementia risk.

Why might dementia affect our ability to smell? 

We still don’t know exactly what the link may be, but researchers have found some possible clues.

The part of the brain responsible for smell is called the olfactory bulb. This lies near where researchers have seen protein buildup in conditions like Parkinson’s disease and Lewy body dementia.

Our olfactory system is closely connected to our limbic system and temporal lobes – regions vital for memory, emotion, and thinking.

Jayant Pinto, professor of surgery at the University of Chicago, who was involved in a study about smell and dementia, previously said: “A rapid decline in the sense of smell is a really good indicator of what’s going to end up structurally occurring in specific regions of the brain.

“We were able to show that the volume and shape of grey matter in olfactory and memory-associated areas of the brains of people with rapid decline in their sense of smell were smaller compared to people who had less severe olfactory decline.”

Which smells might reveal dementia risk? 

In the 2017 study, researchers asked 2,906 men and women, aged between 57 and 85, to complete home interviews and smell tests. None of them had been diagnosed with dementia at the start of the research.

Participants were given a “validated five-item test” which involved smelling samples of strong odours and then selecting where they thought they came from on multiple choice list. 

These smells were: 

Peppermint was the easiest to spot, while leather was the trickiest to identify. 

Almost all participants could identify at least four out of the five smells – 7% only recognised two or three, while just over 2% could only work out one; and 1% didn’t correctly identify any of the aromas.

Five years after the initial test, researchers checked back in on the participants to see who had developed dementia and who hadn’t. 

After adjusting for variables like age and education levels, they learned that people who couldn’t identify at least four of the five smells in the first assessment were about twice as likely to go on to develop dementia than those who could. 

And the worse they scored on the exam, the higher the odds of going on to develop dementia seemed to be. 

Smell loss might be an early sign, not a risk factor 

An editorial about the above study said that while “olfactory dysfunction may precede dementia, by no means could it be considered a factor that causes or increases the likelihood of dementia”. 

After all, it’s not a part of our “exposome” or an illness or social structure. Therefore, the article argued, “the only plausible way to associate it with dementia is to define it as an early sign of the disease, present before other cognitive impairments appear”.

Other research has shown that people who were unable to differentiate between the smell of bubblegum and petrol tended to show early biological signs of Alzheimer’s, like higher levels of dementia-related proteins in their cerebrospinal fluids.

That study’s first author, Dr Marie-Elyse Lafaille-Magnan, said: “This is the first time that anyone has been able to show clearly that the loss of the ability to identify smells is correlated with biological markers indicating the advance of the disease.”