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Worried You May Be Developing Alzheimer's? Check Your Eyes

People worried they might be developing Alzheimer’s may be able to ask their eye doctors to have a quick peek or take a simple smell test.
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People worried they might be developing early signs of Alzheimer’s may be able to ask their eye doctors to have a quick peek during a regular exam, experts reported Sunday. Or they may be able to take a simple smell test.

Four studies being presented at the Alzheimer’s Association International Conference in Copenhagen, Denmark, strengthen earlier evidence that the earliest signs of Alzheimer’s disease might show up in the eyes and nose.

That could mean earlier treatment, and could give people a chance to plan, said Maria Carrillo, vice president of medical and scientific relations at the Alzheimer’s Association.

“There are treatments for symptoms that work best early in the disease process. As time goes on less effective,” Carrillo told NBC News. “We want to get people on those treatments as soon as possible, while they are still useful.”

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There’s no cure for Alzheimer’s, the most common form of dementia, which affects more than 5 million Americans — and it’s projected to soar to 13 million over the next 35 years. A study published earlier this month suggested it’s a big killer, taking down more than 500,000 Americans every year.

Many people might not want to know they have an incurable disease that will take away their identity. But Carrillo said many will want to know. “There are family planning issues for the future, a lot of things to put in place,” she said.

Researchers are working on a blood test for Alzheimer’s, and there are clinical tests that help detect fairly advanced disease. Current biological markers for early disease, including levels of abnormal proteins in spinal fluid, MRI scans of the brain, and brain PET amyloid imaging, are not very accurate, are invasive and can be expensive.

“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 the Alzheimer’s Association’s Heather Snyder.

“We want to get people on those treatments as soon as possible, while they are still useful.”

Alzheimer’s is marked by the accumulation of beta-amyloid "plaques” in the brain. Early study has suggested these proteins also can build up in the eye, perhaps traveling along the optic nerve from the brain.

Shaun Frost of Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) and colleagues tested 40 volunteers using a proprietary supplement containing curcumin, which attaches to beta-amyloid and which is fluorescent, and a new imaging system from NeuroVision Imaging, LLC.

The test detected every one of the Alzheimer’s patients, and correctly ruled out 80 percent of those who did not have it, Frost’s team told the meeting.

“We envision this technology potentially as an initial screen that could complement what is currently used: brain PET imaging, MRI imaging, and clinical tests,” Frost said in a statement. “If further research shows that our initial findings are correct, it could potentially be delivered as part of an individual’s regular eye check-up.”

Dr. Keith Black of Cedars-Sinai Medical Center in Los Angeles, where the device was developed, said the proteins build up in the retina. “The retina, unlike other structures of the eye, is part of the central nervous system, sharing many characteristics of the brain,” Black said.

“By ‘staining’ the plaque with curcumin, a component of the common spice turmeric, we could detect it in the retina even before it began to accumulate in the brain. The device we developed enables us to look through the eye — just as an ophthalmologist looks through the eye to diagnose retinal disease — and see these changes.”

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In a second approach using the eyes, Paul Hartung, president and CEO of Cognoptix, Inc., and colleagues used a laser scanner to detect beta-amyloid in the lens of the eye.

They studied 20 people with probable Alzheimer’s disease and 20 age-matched healthy volunteers. A fluorescent ointment was put in their eyes a day before the exam so it could soak in and stain the deposits in the lens.

This test detected 85 percent of Alzheimer’s cases and ruled out 95 percent of healthy people, they told the meeting. “This system shows promise as a technique for early detection and monitoring of the disease,” Hartung said.

“We’re frustrated that many people in the U.S. who have dementia due to Alzheimer’s or other conditions don’t even have the condition recognized when alive,” said Dr. Pierre Tariot of the Banner Alzheimer’s Institute in Phoenix, who worked on the study.

"It could potentially be delivered as part of an individual’s regular eye check-up.”

Two other studies looked at a smell test for Alzheimer’s. Again, early research has suggested that the disease can affect the olfactory centers of the brain.

Dr. Davangere Devanand of Columbia University Medical Center in New York and colleagues tested 1,037 people in New York City, with an average age of 80. None had Alzheimer’s the first time they were seen in 2004-2006. They were seen again in 2006-2008 and 2008-2010.

They took a standard smell test. “It’s a standardized test which has 40 items, each of which is a scratch-and-sniff item. The person smells it and has to choose the correct choice from four choices,” Devanand told NBC News. “All are very familiar smells, such as gasoline, pizza, tea, apple.”

Over the study 109 people were diagnosed with dementia. “If you score poorly on the test, you are more likely to decline cognitively over time, but by itself it’s not diagnostic that you will definitely decline over time,” Devanand said. “A fair number of people who scored poorly over time did not decline cognitively over time.” But there was a clear trend. For each point lower that a person scored on the test, the risk of Alzheimer’s increased by about 10 percent.

“That is important enough for us to pay attention to,” Carrillo said.

Matthew Growdon and colleagues at Harvard Medical School and the Harvard School of Public Health may have an explanation of why the smell tests works. They tested 215 healthy looking people enrolled in the Harvard Aging Brain Study at the Massachusetts General Hospital.

They gave the same smell test to their volunteers and also measured the size of two brain structures – the entorhinal cortex and the hippocampus, which are important for memory. They also measured amyloid deposits in the brain and administered standard cognitive tests.

People who scored more poorly on the test had a smaller hippocampus and a thinner entorhinal cortex, they told the meeting. This suggests the brain shrinkage associated with Alzheimer’s may affect smell first. “Our research suggests that there may be a role for smell identification testing in clinically normal, older individuals who are at risk for Alzheimer’s disease,” said Growdon.