Scientists flag smell test for Alzheimer’s

by John Ross for The Australian:

Scientists have flagged a smell test for Alzheimer’s disease, raising hopes that the condition can be diagnosed long before it starts to affect behaviour.

A study by researchers from the US Department of Agriculture suggests a distinctive smell in urine, triggered by the disease, could be detected with a simple odour test.

Co-author Bruce Kimball said the work had sprung from research into body odour changes caused by external influences such as viruses and vaccines. “Now we have evidence that urinary odour signatures can be altered by changes in the brain (which are) characteristic of Alzheimer’s disease,” Dr Kimball said.

He said the finding could also have implications for other neurological diseases.

Alzheimer’s is the most common form of dementia, which has surged over the past decade to become the second biggest killer of Australia’s longer living populace. There is no definitive diagnostic test for the incurable condition.

The Philadelphia-based Monell Chemical Senses Centre, which was also involved in the new study, said the disease’s progression could not currently be reversed or even halted. “(But) an accurate diagnosis can give patients and families time to plan for the future and seek treatments for symptom relief,” it said.

The study, published overnight in the journal Scientific Reports, was conducted on mice specially engineered for Alzheimer’s research. The creatures, known as “APP mice”, contain human genes that play a role in plaque accumulations in the brain — a hallmark indicator of Alzheimer’s.

Behavioural and chemical analyses showed that three different strains of APP mice produced urinary odour “profiles” that could be distinguished from those of control mice. The differences stemmed from a shift in the relative concentrations of urinary compounds rather than newly introduced chemicals.

The team found that the different smell appeared before plaque built up in the rodent’s brains, suggesting it was related to an underlying gene rather than pathological changes in the brain.

Co-author Daniel Wesson, of Case Western Reserve University in Ohio, said the research was still at proof-of-concept stage. But it could point the way to human tests, he said.

Extensive research would be needed to ascertain that human tests were feasible, the team said.

Genetically modified mice have also been used to study “olfactory dysfunction” as an indicator of Alzheimer’s. Research suggests that loss of the sense of smell is a powerful sign of impending death.

The study also involved the New York University School of Medicine.

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