Alzheimer’s disease is now the sixth leading cause of death in the U.S., but researchers still do not know what causes the degenerative neurological disorder. In recent years they have pinpointed several genes that seem largely responsible for those cases in which the disorder develops early on, prior to age 60. They have also identified about 20 genes that can increase or decrease risk for the more common late-onset variety that starts appearing in people older than 60.
But genetics simply cannot explain the whole picture for the over five million Americans with late-onset Alzheimer’s. Whereas genetics contribute some risk of developing this version of the disorder, no combination of genes inevitably leads to the disease.
Scientists are now urgently searching for the other missing pieces to explain what causes late-onset Alzheimer’s. Some researchers have shifted their attention from genes to the environment—especially to certain toxins. Their studies of pesticides, food additives, air pollution and other problematic compounds are opening a new front in the battle against this devastating malady. Here’s a roundup of some of the possibilities being studied:
Scientists have already found a strong potential link between pesticides and Parkinson’s disease. Now, a preliminary study released in January suggests that the pesticide DDT, which degrades so slowly that it continues to linger in the environment more than 40 years after the U.S. Environmental Protection Agency banned its use in the U.S., may also contribute to Alzheimer’s.
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