A gene mutation whose discovery was announced Wednesday triples the risk for Alzheimer’s disease. It is a headline that might sound frightening but shouldn’t evoke fear.
The mutation in the gene called TREM2 is rare, occurring in about 1 in 150 people. By comparison one in five people carry a form of a different gene called APO-E that also triples the risk. One in 50 carries a form of APO-E that raises risk 13 times. APO-E’s relation to Alzheimer’s was discovered in 1993. So in terms of public health implications, TREM2 is a small player, and is one of an ever growing list of genes implicated in Alzheimer’s.
The leading contender as the main cause of Alzheimer’s is the accumulation of plaques of protein called amyloid-beta. It is likely that the inflammatory response is attempting to keep that buildup at bay. Last July, Stefansson’s team [one of the researcher's whose work was just published] discovered a different gene mutation, even more rare, that actually protects against Alzheimer’s. That, too, was important science because that gene is responsible for production of amyloid-beta. So it both supports the hypothesis about the cause and leads to ideas about how to make drugs to stop it.
If you know or have known someone with Alzheimer's, as I have, you'll appreciate the fact that we are dealing with not only a serious cause of death, but with a serious cause of distress among the survivors during that painful interval between the onset of the disease and death.