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Reviewed by Arefa Cassoobhoy, MD, MPH
Feb. 25, 2016 -- If a test could tell whether you'll get Alzheimer's disease someday, would you want to know? And if so, what would you do with that knowledge?
These questions are becoming more and more important as researchers close in on tools to predict your risk of Alzheimer's disease decades before symptoms start to appear.
"Primary care physicians, in the disease's early stages, [eventually] could be able to say, 'It looks like there's a problem here' through a blood test, a saliva test, or by looking at the retina," says Dean Hartley, PhD, director of science initiatives for the Alzheimer's Association. "But there's no medical test now. It's all in the research stage."
For now, only genetic tests are available to the general public. They can spot genes linked to a higher risk of Alzheimer's, such as the ApoE4 gene. But genetic tests aren't conclusive. Not everyone whose test result says they have ApoE4 will get Alzheimer's, and many people who don't have that gene will get the disease.
And if you have the gene, there isn't much you can do yet, aside from making lifestyle changes that may be preventive. "You can get the ApoE4 test at your doctor's office, but I and many of my colleagues rarely offer it, because we don't have any treatments to offer if we determine that patients are at higher risk," says Alzheimer's researcher Liana Apostolova, MD, a professor at the Indiana University School of Medicine.
Also, knowing your risk could come with a price. Seven years ago, Jamie Tyrone learned unexpectedly that she had two copies of the ApoE4 gene.
"I went into a deep, dark hole," says Tyrone, 55, a former nurse who lives in San Diego. "This information was very anxiety-provoking, to the point that I was diagnosed with PTSD [post-traumatic stress disorder]. Knowing has done me harm."
Tyrone says Alzheimer's was not on her radar when she was tested for a variety of genetic disorders as part of a research study. Being unprepared for the news, she says, made her anxiety worse.
Eventually she learned to cope. She started to take better care of herself, exercising and improving her diet, meditating and doing brain-twisting puzzles purported to strengthen memory and focus. And she became involved with research into the disease. She founded B.A.B.E.S., Beating Alzheimer's By Embracing Science, a non-profit that supports research into the disease and encourages people to get involved.
Tyrone wants others to learn from her experience.
"I'm choosing to heal by talking about it," she says. "I don't want people to go through what I went through."
New Ways to Detect Alzheimer's Disease
The biggest advance toward the early prediction of Alzheimer's, Hartley says, is using PET scans to show the buildup of beta amyloid plaques in the brain. The plaques are a risk factor for the disease, and in the past they could be seen only during an autopsy.
"This is an opportunity to see into the live brain," Hartley says.
"PET imaging with amyloid will be the first way of approaching prediction," Apostolova says. MRI will also be useful, she says, as will PET imaging for tau proteins, another sign of disease.
But, she continues, amyloid PET scans are expensive, not readily available, and they expose patients to radiation.
"What if there's another way to get at the answer of who's at risk?" she asks.
Research Apostolova led while at UCLA resulted in a simple blood test that picks up biomarkers -- or proteins in the blood -- linked to Alzheimer's. Along with other tests, it one day may help predict the disease. She published her early findings in January in the journal Neurology.
Researchers are studying several other new tests:
- A saliva test that identifies biomarkers linked to Alzheimer's disease.
- A combination of cognitive tests, MRI scans, and analysis of proteins found in cerebrospinal fluid -- fluid in the brain and spinal cord that can predict mild cognitive impairment, or thinking problems, 5 years before symptoms become apparent.
- Measurements of the protein neurogranin, a potential Alzheimer's biomarker found in fluid in the brain and spinal cord.
- Tests that uncover the deterioration of your sense of smell may indicate Alzheimer's.
- Eye exams that can measure beta amyloid buildup.
All of these tests remain experimental, and their effectiveness remains to be seen.
"Saliva tests, blood tests, and things like that are not ready for prime time," Hartley says.
Knowing Your Risk
If you do learn your risk of Alzheimer's -- through a genetic test or, eventually, through one of these still-experimental tests -- what can you do with that knowledge? And how would it affect you? After all, with no viable treatments available to slow, stop, or prevent the disease -- only drugs that may improve symptoms in some people for a short time -- there's little doctors can offer you.
"Some people would want to know so they can plan things out, such as long-term care insurance and end-of-life decisions, while others would not want to know," says David Salmon, PhD, of the Shiley-Marcos Alzheimer's Disease Research Center at the University of California, San Diego. "It's a personal decision. It's hard to say what the best advice would be."
Salmon's research suggests that knowing you're at risk can have bad consequences. You're more likely to rate your memory worse and do worse on a memory test than someone with the same risk who is unaware.
"We don't think it's depression, but we didn't measure anxiety and stress, so we don't know if the disclosure increased anxiety and that it's the anxiety that causes you to have memory problems," Salmon says.
But other research suggests that knowing your genetic risk does not up your chances of depression, anxiety, or distress. Jason Karlawish, MD, an Alzheimer's expert and medical ethicist at the University of Pennsylvania, has studied middle-age adults with a family history of Alzheimer's.
If people get their mood and well-being assessed before they get tested, "they have minimal problems with mood and well-being after learning the results," Karlawish says. "We don't have data from persons who are older and plausibly closer in age of onset to AD."
Karlawish is involved in a study of an experimental Alzheimer's drug known as solanezumab. The drug, made by Eli Lilly, targets amyloid plaques and may delay the onset of cognitive decline. It is now being tested on people who don't have Alzheimer's symptoms but whose PET scans have shown the presence of such plaques, a potential early warning sign of the disease.
It's among several meds that may prevent or slow Alzheimer's from getting worse that are being studied in people long before they show symptoms.
Karlawish's previous research suggests that that knowledge may motivate people to change their lifestyles. That's what Tyrone eventually began to do. She has improved her diet and her exercise habits, she's at work on a book about her experiences, and she's become involved in Alzheimer's research, such as studies into new medication. That's something she highly recommends -- as does Karlawish -- for people who know they're at risk.
"Yes, it's partially selfish, because you're getting something as well as giving something," she says. "You're at the forefront of cutting-edge research."
But if you don't yet know? "I would ask them, why do you really want to know this information? And can you make changes without knowing that information?" Tyrone asks. "It may be anxiety provoking. Is it really healthy to know this information or is not healthy? What are you going to do with it?"
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