Sniffing out Dementia

Cognitive decline was more likely in people who had changes to their sense of smell

(RxWiki News) Simple memories, like being able to identify a smell, can be affected in later stages of dementia. However, research suggests that changes in smell memory may show up early.

A recent study found that people who had trouble with knowing one smell from another were more likely to show cognitive decline three years later.

A simple smell test may be helpful in diagnosing dementia.

"Report any memory problems to your doctor."

The study, led by Hamid Sohrabi, PhD, of the School of Medical Sciences at Edith Cowan University in Australia sought to build on earlier research that showed a link between changes in memory for smell and dementia.

They performed a smell test, called Sniffin’ Sticks, on 308 people between the ages of 46 and 86 who had no signs of cognitive impairment.

Sniffin’ Sticks uses felt-tip pen like sticks containing odors of various intensities. The test measures a person’s ability to detect faint odors, identify smells, and discriminate between smells. Each of these items yields a score, and together they provide a measure of memory for smells.

The researchers followed up with the people three years later, and based on a standard cognitive test, they divided them into two categories: cognitively declined or not.

They found that loss of function in discrimination for odors predicted cognitive decline but not deficits on identification. Meaning, people who had trouble knowing that two smells were different from one another were more likely to have cognitive impairment three years later.

The study also found that people who were older at the beginning of the study were more likely to develop cognitive impairment, so they re-examined the scores taking age into account.

Lower scores on odor discrimination were still predictive of cognitive decline even when they accounted for age.

The authors concluded that odor tests are cheap and easy to administer and can be a useful tool in identifying early stages of cognitive decline and people at-risk for dementia.

Changes in smell may precede cognitive symptoms and could serve as a tool for diagnosis and risk assessment.

Sniffin’ Sticks and other similar tests are fairly low cost (around $300 US retail) and simple to perform.  However, more research is needed to understand the best way that doctors can implement this type of assessment along with other types of cognitive tests.

This study was published in May in Translational Psychiatry. The research was funded by grants from the Australian National Institute of and the McCusker's Alzheimer's Research Foundation.

Authors in this study report affiliations with Pfizer, Wyeth, Alzhyme, and other pharmaceutical and biotechnology companies.

Review Date: 
August 2, 2012