PHILADELPHIA, Jan. 14 (UPI) -- Researchers found a distinctive odor in urine may allow for earlier diagnosis of Alzheimer's disease based on experiments with mice, according to a new study.
While the disease is unique to humans, and experiments with mice require models of brain disease that mimic Alzheimer's be created by scientists, the mouse biomarker suggests a non-invasive test could be used to detect the same thing in people.
Alzheimer's disease is difficult to diagnose, and lacks a definitive test for living people, making the potential to confirm its effects -- rather than deduce a diagnosis based on cognitive tests -- could help doctors to treat it much earlier.
A smell test to diagnose Alzheimer's is not a completely new concept, though previous research suggested testing a patients' sense of smell using peanut butter, as the disease affects it.
"Now we have evidence that urinary odor signatures can be altered by changes in the brain characteristic of Alzheimer's disease," said Dr. Bruce Kimball, a chemical ecologist at the USDA National Wildlife Research Center, in a press release. "This finding may also have implications for other neurologic diseases."
For the study, published in Scientific Reports, researchers used three modified mouse models simulating Alzheimer's disease in humans, analyzing their behavior and chemical changes in their urine. Compared to control mice without the genetic changes, changes in odor were tied to differences in the concentration of compounds already present in urine.
The researchers said the differences in odor preceded buildup of plaques in the brains of altered mice similar to those found in humans with Alzheimer's. The changes in urine, they said, indicate a genetic cause -- like the disease -- rather than physical changes in the brain typical of the disease.
Future research in humans is needed to identify and understand changes caused by Alzheimer's, but researchers are hopeful.
"While this research is at the proof-of-concept stage, the identification of distinctive odor signatures may someday point the way to human biomarkers to identify Alzheimer's at early stages," said Dr. Daniel Wesson, a neuroscientist at the Case Western Reserve University School of Medicine.