How Your Sense of Smell Could Help Detect Dementia

While deteriorating eyesight is a common side effect of ageing, a new study suggests that an impaired sense of smell could be an early warning sign of dementia, as well as heart and neurodegenerative diseases.

Co-authored by Prof Honglei Chen, the study explored the link between quality of sense of smell and the onset of diseases like Parkinson's. It also looked at more wide-ranging links, including how sense of smell is related to the immune system and the development of psychiatric disorders.

“My suspicion is [the] process of smell in older adults probably has much broader potential health implications than what we already know about,” explains Chen.

Poor sense of smell linked to 46% increase in risk of death

The findings were published in the Annals of Internal Medicine and analysed Brief Smell Identification Test (BSIT) results from more than 2200 participants aged between 71 and 82. The same tests were carried out again 13 years later, with the team grouping participants into “good”, “moderate” or “poor” categories depending on their sense of smell.

After factoring in variables like age, sex, smoking and overall health, the team found that participants with a "poor" sense of smell were 46% more likely to die within 10 years than their "good" counterparts. Specifically, they found that inferior sense of smell was linked to deaths caused by Parkinson’s disease and dementia, though there was no link found for deaths caused by respiratory diseases or cancer.

"Poor olfaction among older adults with excellent to good health may be an early warning sign for insidious adverse health conditions that eventually lead to death,” reads the study.

Impaired olfaction could emerge as early warning sign

The study received widespread acclaim from industry experts, with Professor Jayant Pinto of the University of Chicago saying priainsg Chen and his team for breaking new ground.

“While we still need to understand what exactly a poor sense of smell is signalling in terms of specific mechanisms that lead to increased risk of death, it seems clear that impaired olfaction is an early warning sign of both diseases such as Alzheimer’s and Parkinson’s, as well as heart disease,” he says.

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