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Environmental toxins and Alzheimer's Disease
It is always good to see a wider net being cast in the attempt to understand the causes of Alzheimer's disease. This is the most recent example:
Increasing age is the most important known risk factor for Alzheimer’s disease, but many other risk factors — including environmental exposures — are poorly understood. Previous studies of Swedish twins by USC’s Margaret Gatz suggested that half of individual differences in Alzheimer’s disease risk may be environmental.
The two classes of Alzheimer’s disease genes are considered in the exposome model. One class called familial Alzheimer’s genes are dominant, meaning someone who inherits those genes will ultimately develop Alzheimer’s. The other class include gene variants like apolipoprotein E4 (APOE4), where risk increases along with more copies of the genes. Among carriers of APOE4, a few people reach age 100 and older without ever developing the disease — demonstrating environmental risk is contributing to that variability.
Cited in their article is a study that showed the onset of dementia was a decade earlier for carriers of a dominant Alzheimer’s gene living in cities and who came from lower socioeconomic backgrounds or less education.
“Environmental factors, including exposure to air pollution and low socioeconomic status, shifted the onset curve by ten years,” explained Finch. “It’s in the research literature but until now, no one has paid sufficient attention to it.”
One of the best examples of this is that families in Colombia develop Alzheimer's disease about a decade earlier than family members with the exact same presenilin-1 gene mutation in Japan. The families in Colombia are exposed to some of the highest levels of mercury contamination (due to mining operations) in the world while families in Japan often have a high antioxidant diet which includes green tea and rice bran oil. The gene determines that someone will get Alzheimer's disease but other factors determine the age of onset.
Just want to mention that Dr. Bredesen, in The End of Alzheimer's, identifies several toxins including mercury in his book as causes for dementia for some people. He also suggests lab tests and treatment protocols depending on each person's unique situation. He states that individuals with this type of dementia may be the hardest to turn around. Have you read the book?
I think looking at environmental toxins is important not just for dementia, but health in general. You have to wonder about so many neurological, autoimmune and cancers and how toxins may contribute...and why does it happen to some people and not others.