A new report about highly accurate prediction of Alzheimer's based on a spinal tap test gives us all cause to ponder: If foreknowledge about vulnerability to Alzheimer's is on a need-to-know basis, who needs to know?
This advance about testing for failing memory also invites us to remember something, namely, what screening tests are for.
In the several editions of the epidemiology text I have coauthored, we define medical screening tests and delineate the criteria on which they are based. We may reasonably spare ourselves the details here, but the gist is this: you only go looking for trouble you can do something about. You screen when finding a disease or risk factor early allows you reliably to change outcomes for the better.
What we know of the new Alzheimer's test thus far is that it seems to be highly accurate in people whose memories have already begun to fail. Whether or not it performs as well before symptoms of dementia develop and advance remains to be seen. While my hope is that an advance in diagnostic testing for Alzheimer's may portend advances in treatment, I see little intrinsic value in being able to attach a specific label to inexorably failing memory with greater confidence. Thus far, the new test does not usher in any advance in treatment, and offers nothing related to prevention.
But we don't need a new test, and we certainly shouldn't wait for memory impairment to defend ourselves against Alzheimer's. While the disease, which tends to run in families, clearly has genetic underpinnings, it is overwhelmingly a condition of vascular decline. Keep your blood vessels healthy -- by eating well, being active and not smoking -- and you very decisively reduce your risk of dementia, along with that of heart disease and stroke.
Any advance in our understanding of Alzheimer's is welcome news. But before rushing out for any new test about what failing memory might mean, we should avoid failing to remember what such testing is for. Until the knowledge from testing provides the power to change outcomes, there is, in my estimation, no particular need to know.
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