Most people associate the early stages of dementia with symptoms such as getting confused or struggling to recall details, but now scientists have revealed something that could be far more telling.
The new study has shown that struggling to distinguish between the smell of bubblegum and petrol could be an early sign of the disease, years before it starts to affect your everyday life.
Researchers have long speculated that changes in your ability to smell correctly could be tied to the onset of Alzheimer’s disease, as much as twenty years before any red flags would be raised in your day-to-day behaviour.
Marie-Elyse Lafaille-Magnan, first author on the study, said: “For more than 30 years, scientists have been exploring the connection between memory loss and the difficulty that patients may have in identifying different odours.”
Despite knowing this, they didn’t have any way to tell this early on and weren’t entirely sure why this happened.
Now the team at McGill University, Canada, have suggested that one of the first changes when dementia begins may be damage to the olfactory neurons, which distinguish between different aromas.
In order to test their theory, they asked 300 people at high risk (because their parents have the progressive neurological condition) to take scratch-sniff tests to identify strong scents such as petrol, bubblegum and lemon.
And a third of these participants also agreed to have regular lumbar punctures to test the quantities of various AD-related proteins present in the cerebrospinal fluids - a biomarker of the disease.
The researchers found that those with the most difficulty in identifying odours were those in whom other indicators of Alzheimer’s were most present.
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.
“This makes sense because it’s known that the olfactory bulb, involved with the sense of smell and the entorhinal cortex, involved with memory and naming of odours, are among the first brain structures first to be affected by the disease.”
According to the Alzheimer’s Society there are around 800,000 people in the UK with dementia. One in three people over 65 will develop dementia, and two-thirds of people with dementia are women.