The early stages of Alzheimer’s disease could be detected by smell years before memory loss sets in, a study found.
The disease is the most common type of dementia, affecting almost 500,000 people in the UK and results in the gradually loss of mental ability linked with gradual death of brain cells.
The first sign is usually minor memory problems but because symptoms progress slowly, it can be difficult to recognise there is a problem.
But discovery the disease that will affect an estimated one in every six people over the age of 80 could help doctors try and mitigate the effect.
Now US scientists have found the disease leaves an odour biomarker in urine well before the significant development of Alzheimer-related brain pathology such as amyloid plaque deposits in the brain.
The breakthrough could provide early diagnosis of Alzheimer’s and other neurodegenerative disorders through a simple non-invasive urine test.
Dr Bruce Kimball, a chemical ecologist with the US Department of Agriculture’s National Wildlife Research Centre said: “Previous research had focused on body odour changes due to exogenous sources such as viruses or vaccines.
“Now we have evidence that urinary odour signatures can be altered by changes in the brain characteristic of Alzheimer’s disease.
“This finding may also have implications for other neurologic diseases.”
The breakthrough was made in mice studies and further extensive studies are needed to identify and characterise Alzheimer’s-related odour signatures in humans.
Assistant Professor Dr Daniel Wesson at the Case Western Reserve University School of Medicine said: “While this research is at the proof-of-concept stage, the identification of distinctive odour signatures may someday point the way to human biomarkers to identify Alzheimer’s at early stages.”
The study published in the journal Scientific Reports involved the study of three separate mouse models, known as APP mice, which mimic Alzheimer’s-related brain pathology.
The odour changes did not result from the appearance of new chemical compounds, but instead reflected a relative shift of the concentrations of existing urinary compounds.
The odour differences between APP and control mice were mostly independent of age and preceded detectable amounts of plaque build-up in the brains of the APP mice.
These findings suggested the characteristic odour signature is related to the presence of an underlying gene rather than to the actual development of pathological changes in the brain.
Additional studies showed that the distinctive odour profiles could be used to predicatively identify APP mice versus control mice.
by Tony Whitfield