A new research has suggests that loss of a sense of smell may be an early indication of Alzheimer's disease.
Scientists found that changes linked to the most common form of dementia begin in mice in an area of the brain responsible for recognising smells.
The physical symptoms coincided with impaired olfactory, or smell, function. Affected animals had to sniff odours for longer to remember them than healthy mice. They also had problems differentiating between smells.
According to researchers, noticing similar changes in humans may help in the early detection of Alzheimer's, before the disease has done lasting damage to the brain.
Reduced smelling ability in the genetically engineered mice was linked to the appearance of amyloid plaques - sticky lumps of protein in the brain that are believed to play a key role in Alzheimer's.
"What was striking in our study was that performance of the mouse in the olfactory behaviour test was sensitive to even the smallest amount of amyloid presence in the brain as early as three months of age (equivalent to a young adult)," Daniel Wesson, one of the scientists from the New York University School of Medicine, said.
"This is a revealing finding because unlike a brain scan, a laboratory-designed olfactory test may be an inexpensive alternative to early diagnosis of Alzheimer's," he added.
Professor Ralph Nixon, director of the Centre of Excellence on Brain Ageing at the New York University Langone Medical Centre, said: "These novel results provide a two-fold benefit, not only in confirming that olfactory problems may serve as an early indicator of Alzheimer's, but that further validation in humans could facilitate testing of new therapies for the disease."
The findings were published in the Journal of Neuroscience.