Sense of Smell Also May Be a Way to Screen
A mature man’s eyes looking up. Getty Images
COPENHAGEN—Efforts to detect Alzheimer’s disease earlier and more cheaply are focusing on signs of the ailment in the eye and sense of smell.
Scientists have found that certain biological changes in the retina and lens of the eye, and in the sense of smell, may help predict whether people with no or minor memory issues may go on to develop the progressive brain disease, according to findings presented here Sunday at the Alzheimer’s Association International Conference.
Alzheimer’s disease is diagnosed primarily by clinical examination using memory tests and questions about how a patient is functioning. But researchers are attempting to devise tools, particularly using biological markers, to improve the detection of early stages of the disease, said David Knopman, a neurologist at Mayo Clinic and a member of the Alzheimer’s Association Medical and Scientific Advisory Council.
The disease’s pathology in the brain typically begins decades before the appearance of memory symptoms.
Looking for changes in the eye or smell represent “simpler, less invasive” methods that are more feasible for use in doctor’s offices and other clinical settings, Dr. Knopman said.
Since there aren’t yet any treatments that stop the progression of Alzheimer’s—and some people may not want to know they face a devastating disease without a cure—earlier detection primarily could be helpful for research purposes in identifying people who are good candidates to participate in prevention trials and to monitor brain changes that occur as the disease progresses.
Many experimental disease-modifying treatments are under development. Once such a treatment is available, the hope is to identify people at greater risk of Alzheimer’s and give them the treatment before they exhibit memory symptoms.
Currently, brain imaging can be used to detect one major pathology associated with the disease—clumped deposits of the protein amyloid—but it is expensive and used primarily for research, not in doctors’ offices.
Efforts to develop blood-based tests for Alzheimer’s generate much excitement among the public but none are ready for prime time yet, experts say.
But amyloid plaques found in the brain also are known to be deposited in the eye. Two company-funded studies found that those deposits can be detected through noninvasive eye-imaging technology and are highly correlated with the amyloid results from brain imaging.
Cognoptix Inc., a closely held biotech company in Acton, Mass., focuses on amyloid detection in the lens of the eye. CSIRO Australia, the country’s national science agency, and its Sacramento, Calif.-based partner, NeuroVision Imaging LLC, have been studying the retina, in the back of the eyes.
The retina is like a “piece of brain outside the brain,” said Shaun Frost, a researcher at CSIRO Australia.
The first 40 patients in a 200-participant study showed that retina changes correlated strongly with amyloid plaque development in the brain. The full study will be completed this year, according to Dr. Frost.
It remains to be seen whether eye imaging will prove better than memory tests at detecting Alzheimer’s. There has been limited research to track whether early signals in the eye actually predict development of the disease.
Smell is another area of interest because the odor center of the brain appears particularly vulnerable to Alzheimer’s pathology and the ability to identify different smells becomes impaired relatively early in the disease process.
A study of some 1,000 individuals without Alzheimer’s diagnoses who were examined from 2004 to 2006, using a simple scratch-and-sniff smell test known as the UPSIT, showed that lower scores on the test were associated with a greater risk of developing Alzheimer’s—even if the individual was cognitively normal at the beginning of the study, said Davangere Devanand, a Columbia University psychology and psychiatry professor.
Researchers cautioned that more work is needed and that a number of other factors can influence smell, including smoking and ailments such as Parkinson’s and schizophrenia.
Write to Shirley Wang at firstname.lastname@example.org
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