Genetic Testing: APOE won't tell you if you will get Alzheimer's Disease
As a psychologist, you learn not to tell people at a dinner party what you do for a living unless you want to jokingly/not jokingly be asked if you are trying to psychoanalyze everyone. Most of the time it is easier to say you specialize in dementia research or care, and I don't mind hearing the stories people tell me. However, a few years ago, the conversation took an unexpected turn while talking to a salesperson. The young woman, likely in her 30s or 40s, had gotten commercially available genetic testing, which came back saying she had the APOE4 double allele, and thus was going to get Alzheimer's disease. She became tearful telling me, took the news from the commercial company as absolute fact, and asked what she should do to prepare.
Now, she wasn't my patient - in fact, I was her client! - but I reassured her that genetic testing was not the entire picture, and I did not believe it was accurate that she had the almost certain fate of having Alzheimer's disease one day. I told her to talk to her doctor if she was worried. I don't know what happened from there on her end. I will tell you I was surprised and angry that a company was just casually telling folks about genetic risk for serious diseases that may or may not even be accurate.
Genetic testing for Alzheimer's for someone who is normal in cognitive function is not a good predictor that you will or will not one day get the disease. Your risk may go up, but that doesn't mean you are going to get it. People tend to think it tells them more definitively about their risk than it does. The same goes for having a family member with dementia. Just because your mother had dementia, it does not mean you will have it. Your risk goes up, but your overall chances remain quite low. I find people more often think their risk is higher.
This recently published article by JAMA Network (that includes Mayo Clinic staff), does a nice job of presenting these facts in a clear way.
Be sure to scroll down to look at the tables that give risk levels.
Bottom line: Your risk does go up if you have the APOE4 allele, but in no way predicts that you will or will not go on to have Alzheimer's disease.
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