Smell test may help identify people at Alzheimer's risk

New York: Researchers at Massachusetts General Hospital (MGH) in the US have developed a method to identify those at risk for Alzheimer's disease on the basis of their ability to recognise and recall odours.

The non-invasive protocol testing the ability to recognise, remember and distinguish between odours was able to identify older individuals who -- according to genetic, imaging and more detailed memory tests -- were at increased risk of Alzheimer's disease, the study said.

"There is increasing evidence that the neurodegeneration behind Alzheimer's disease starts at least 10 years before the onset of memory symptoms," said principal investigator Mark Albers of the MGH Department of Neurology. 

"The development of a digitally-enabled, affordable, accessible and non-invasive means to identify healthy individuals who are at risk is a critical step to developing therapies that slow down or halt Alzheimer's disease progression," Albers noted.

It is well known that brain circuits that process olfactory information can be affected by Alzheimer's disease, and several studies have documented a diminished ability to identify odours in affected individuals. 

The study recruited 183 participants, most of whom were enrolled in ongoing studies at the MGH-based Massachusetts Alzheimer's Disease Research Center. 

At the time of the olfactory testing, 70 were cognitively normal, 74 tested normal on cognitive tests but were personally concerned about their cognitive abilities, 29 had mild cognitive impairment and 10 had been diagnosed with possible or probable Alzheimer's disease. 

Results of the test significantly differentiated among the four groups of participants, and those results correlated with the thinning of two brain regions -- the hippocampus and the entorhinal cortex -- previously associated with Alzheimer's risk. 

The researchers also found that participants' ability to remember a previously presented aroma also showed significant differences between the two cognitively normal groups and participants with Alzheimer's disease, whose results were no better than chance.

Poor performers in the memory test were more likely to have the variant of the APOE gene associated with increased Alzheimer's risk, said the study published online in the journal Annals of Neurology.