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DDT, other Environmental Toxins Linked to Late-Onset Alzheimer’s Disease
Scientists
suspect that, along with genetic factors, toxins and pollutants may increase
the risk of developing this debilitating disorder
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:
DDT (dichlorodiphenyltrichloroethane)
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.
Jason Richardson and his team at Rutgers University tested blood samples of
people with and without late-onset Alzheimer’s. They found that most
participants with the disease had levels of DDT and DDE (a metabolite of DDT)
four times greater than the control group. Researchers also observed that
participants with the most severe cases of Alzheimer’s had both a genetic
predisposition and high pesticide blood levels, indicating that DDT/DDE may
interact with genes to trigger the disease.
Richardson doesn’t have a definitive mechanism for how DDT exposure might lead
to Alzheimer’s, however. But he speculates that DDT/DDE somehow encourage
growth of the amyloid proteins that make up the plaques associated with the
disease. He emphasized that his study is preliminary and his results will have
to be replicated by future research on a larger scale.
In addition, some of the findings seem to contradict the study’s main
conclusion. “The people I find most interesting are the ones who have really
high levels of DDT and DDE, but don’t have Alzheimer’s,” Richardson says,
“Maybe we’re a little early on those guys and they’ll ultimately end up with
the disease. Or what would be more interesting is if their genetic makeup or
lifestyle protects them from the disease.”
To read
more: http://www.scientificamerican.com/article/studies-link-ddt-other-environmental-toxins-to-late-onset-alzheimers-disease/?WT.mc_id=SA_Facebook
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