Thu 16 Aug, 2012 11:33 am
Grappling With The Uncertainty Of Alzheimer's Testing
by Michelle Andrews - NPR
August 16, 2012
When does it make sense to test a person for the risk of an incurable illness?
Counselors have long cautioned about the downsides of genetic testing for Alzheimer's disease.
For one thing, the current genetic tests for late-onset Alzheimer's — the type that develops after age 60 and is responsible for more than 90 percent of cases — only indicate a probability of getting the disease. It's not definitive. And consumers' ability to buy life insurance or long-term care coverage could be jeopardized by the results.
But there's another reason some doctors and counselors have discouraged testing: Concern that if people learned that they were at higher risk for developing a serious, incurable neurological disease, it might prove profoundly distressing.
Those worries have proved unfounded so far. An ongoing series of studies has found that people manage just fine when told their results, thank you very much, even if the results indicate that their risk of developing Alzheimer's is higher than average.
Many factors likely influence the development of Alzheimer's disease, including genes, lifestyle and the environment. To date, one gene in particular has been identified as providing a strong indication of risk for the disease: the apolipoprotein E (APOE) gene on the 19th chromosome. There are three versions of the gene—dubbed E2, E3 or E4-and everyone inherits one version, or allele, from each parent. People with one or two E4 alleles have an up to 15 times greater risk of developing late-onset Alzheimer's disease.
The studies, called Risk Evaluation and Education for Alzheimer's Disease (REVEAL), got started in 2000 to test how asymptomatic people reacted to learning their genetic risk, based on the APOE gene. The first study examined 162 adult children of people with Alzheimer's. Subsequent studies tested other variables, adding more African-Americans to the subject pool, for example, or disclosing the results by phone instead of in person.
At the time of the original study, "there was a resounding consensus that no way should you be sharing APOE information with people," says Dr. Robert Green, a lecturer in genetics at Brigham and Women's Hospital in Boston and co-author of papers about the work.
But the study, which followed people for a year after they learned their results, found that people who knew their APOE genetic status were no more anxious or depressed about their chances of developing Alzheimer's than those who didn't. This was true even for subjects who had the E4 genetic variant that conferred the highest risk.
Despite limitations of the test, people in the study said there were many reasons they wanted to be tested, including arranging their personal affairs, making decisions about long-term care insurance and preparing their family for the possibility that they might become sick.
Interest in this type of testing is only going to continue to grow, says Green. "Whether we recommend tests or not, the world is changing and people are starting to want to know about their own DNA," he says.
Aside from insurance issues, a diagnosis of Alzheimer's can limit your ability to legally drive. Doctors in California, and possibly other states are required to report the diagnosis to the state.
Go deal with that bureaucracy if you want an interesting day.
I've known I was at risk since age 30 or perhaps before - with all those grand aunts when I was a kid - even though at the time I didn't know the word Alzheimer's. That was forty years ago.
(Er, sorry, I understand laboratory testing; no ill will meant to the scientists working this out)
If and only if I still lived in west Los Angeles, I'd go present myself at whatever the department is at UCLA Med that used to be called NPI, for neuropsychiatric institute. Or, I think I would.
I figure there are new names for different departments. From my readings. there are some alzheimer's smarties there, working on all this. For them I'd volunteer.
They already have my dna on file, how worked out and notated I don't know, but I was part of a dna study re genetics of retinitis pigmentosa by an expert at the Jules Stein Eye Institute, then down the hall from NPI. I know I was an outlier on that, and gather they take mine as a birth defect.
I meant to say I was a patient sample by a guy participating in a dna study re RP. I don't remember when that was, guessing early nineties.
My wife and I were discussing this disease a few days ago, because she's watching a Korean tv show with a young women diagnosed with it. My wife was telling me that early cases of the disease kills the patient earlier than if contracted later in life.
There's a famous family with it in a latin american country - I'm forgetting, hah - maybe or maybe not Colombia. Folks in that family get it early and bad.
Contracted earlier in life?
I don't think of it as contracted, as in by some vector. I think of it as genetic, with perhaps some triggers or enhancers in the run of life.
My mother's family was thick with the symptoms. Scary thick.
My father's, I don't know much about. My father had huge problems and died hard but I don't think I can put that to alz. His mother died of diabetes and heart related stuff. His father was in a nursing home (found by a friend who is a genealogy fan), but at something like 86 - to which I say what does that mean.
So, at this point, I'm rooting for my father's genes.
I think he means early-onset. The progression is supposedly much faster when diagnosable symptoms strike prior to age 60.
I think he means early onset too.
I take the word contracted
as meaning a virus or bacterium or ricketsia or priam (sp?) or that a mosquito or rats carrying vectors gave you something - sort of like the Tarantula in a Bond movie coming into your room.
I don't know if that is the common use of the word - it's my take, that you somehow met a virus in a hallway.
I probably should have used another word, but I meant "to catch or develop a disease." Early onset is a good word in this case.
Aside from insurance issues...
That would be enough to prevent me from being tested. I just read that the CDC is recommending anyone between the ages of 47 and 67
be tested for HCV. Um.... no.
catch and develop have different meanings, CI. Catch a cold means you were exposed to a virus and the virus got a foothold and your nose started running. Develop could mean that something you were genetically in line for became activated. You didn't catch it, it was there already.
Even if the person is predisposed to alzheimers, it's my understanding some may or may not come down with the disease. From that respect, I think "catch" is a reasonable word.
Think what you like, of course.
(Meantime, thank you for the Cheetah Photo, T.)