Gum or petrol? Sense of smell linked to dementia

PEOPLE who struggle to distinguish between the smell of bubblegum and petrol could be at risk of developing dementia, a study suggests.

Scientists believe that changes in smell could be one of the first signs that a person is suffering from early stages of Alzheimer’s disease (AD). It is thought that the first damage to the brain from dementia occurs up to 20 years before any symptoms appear, but currently there is no way to tell if is happening.

But scientists at Mcgill University, Canada, believe that one of the first changes may be damage to the olfactory neurons, which distinguish between different aromas.

They tested their theory on 300 people who were at high risk of developing Alzheimer’s disease because they had a parent who had suffered from the condition. They were asked to take multiple choice scratch-and-sniff tests to identify strong scents, such as bubblegum, petrol and lemon.

One hundred also volunteered to have regular lumbar punctures to measure the quantities of various Adrelated proteins present in the cerebrospinal fluid. The researchers found that those with the most difficulty in identifying odours were those in whom other, purely biological indicators of Alzheimer’s disease, were most evident.

“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,” says Marie-elyse Lafaille-magnan, a doctoral student at Mcgill and the lead author of the study.

“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.

“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.”

Around 800,000 people in Britain are suffer from dementia in Britain, and most have Alzheimer’s disease.

The research was published in the journal Neurology.