Loss of smell sense may be 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 other healthy mice. They also had problems differentiating between smells.

Noticing similar changes in humans may help in the early detection of Alzheimer's, before the disease has done lasting damage to the brain, say the researchers.

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.

Daniel Wesson, one of the scientists from the New York University School of Medicine, said: "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).

"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."

The findings were reported in the Journal of Neuroscience.

The director of the Centre of Excellence on Brain Ageing at the New York University Langone Medical Centre, Prof Ralph Nixon, 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."

Around 700,000 people in the UK suffer from dementia, almost two thirds of whom have Alzheimer's.