As with genetic tests for Huntington's, Alzheimer's has no cure. How knowing you're at the door of a horrible death is of benefit, I could not say.
But what if you're decades away from it, and what if it might be possible to take some action to prevent it?
That's what David Bunce (right), an Australian currently working at Brunel University in England, claims in a paper at PLoS One describing what he calls a 30-second screening test for the disease that can be conducted on people in their 40s. (Picture from the Australian National University.)
A test of reaction times, he wrote, can identify people who might have rice-sized lesions in that portion of the brain devoted to memory. An inconsistent result is the danger signal, he wrote. Consistently fast or slow times indicate lesions are unlikely to be there.
The efficacy of the test was demonstrated by brain scans of 428 participants, all between 44 and 48, 15% of whom had the lesions.
In his paper Bunce suggested the test can help doctors prescribe lifestyle changes or drugs that might delay the onset of symptoms until you have time to die from something else.
Before going on, let's be clear. As I wrote last month, many medical studies are wrong, especially in small studies, in hot areas of research, where the researcher's career is wedded to the idea of being right. All true in this case. (Also note, those are indicators something may be wrong, not proof they are wrong.)
But here's the real kicker. Will those "changes" in diet and lifestyle Bunce holds out hope for help?
Another paper delivered this week, in Neurology, indicates cholesterol levels in middle age are actually a poor predictor of risk.
The result contradicts a large study last year indicated a link between high levels of cholesterol in mid-life and later onset of Alzheimer's. Doctors have been looking at cholesterol as a predictor for dementia because the amyloid plaques, indicating the disease is coming on, are composed of similar stuff.
This idea, that heart health and later brain health may be linked, has been controversial since it was first proposed. But it remains comforting, the idea that controlling a single number will keep you alive.
Maybe too simple, it turns out.
Michelle Mielke of Johns Hopkins looked at a 32-year study of Swedish women, almost 10% of whom eventually suffered dementia, and found no link between cholesterol levels in middle age and dementia in old age.
There was, however, a risk associated with rapid decreases in cholesterol levels entering old age, when they were not the result of using statin drugs, Mielke's paper said. The risk of later Alzheimer's was up 17.5% for this group.
So, do you want to take the Bunce test? Especially if we are not certain what you should do about it?