Smell, eye tests may detect Alzheimer's early

While scientists are closer to developing a blood test to predict the onset of Alzheimer's disease, Indian-origin professor Davangere Devanand and other researchers have found our eyes and sense of smell could well hold the key to detecting the disorder early in a cheaper and easier way.

A decreased ability to identify odour might indicate the development of cognitive impairment and Alzheimer's disease, while examinations of the eye could indicate the build-up of beta-amyloid, a protein associated with Alzheimer's in the brain, the findings of four research trials showed.

"In the face of the growing worldwide Alzheimer's disease epidemic, there is a pressing need for simple, less invasive diagnostic tests that will identify the risk of Alzheimer's much earlier in the disease process," said Heather Snyder, director of medical and scientific operations, Alzheimer's Association.

Early detection is essential for early intervention and prevention, when new treatments become available, Snyder noted.

Clinically, at this time it is only possible to detect Alzheimer's late in its development, when significant brain damage has already occurred.

Beta-amyloid protein is the primary material found in the sticky brain "plaques" characteristic of Alzheimer's disease.

In a study led by Devanand, professor of psychiatry at Columbia University Medical Centre in the US, researchers investigated a multi-ethnic sample of 1,037 non-demented elderly people in New York City and found that in 757 subjects who were followed, lower odour identification scores on a smell identification test were significantly associated with the transition to dementia and Alzheimer's disease.

"Odour identification deficits were associated with the transition to dementia and Alzheimer's disease, and with cognitive decline in cognitively intact participants, in our community sample," Devanand noted.

In a separate study researchers found that amyloid levels detected in the retina were significantly correlated with brain amyloid levels as shown by PET (Positron emission tomography) imaging.

The results of the studies were reported Sunday at the Alzheimer's Association International Conference in Copenhagen, Denmark.