Shadowing Trump's attacks on mental fitness

Shadowing Trump's attacks on mental fitness -- his own father's
dementia
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While much remains unknown about Alzheimer's, experts say there is an
increased risk of inheriting a gene associated with the disease from a
parent.
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Trump's father's condition also drove a wedge into his family, which
fell into years of lawsuits that alleged in part that Donald Trump
sought to take advantage of his father's dementia to wrest control of
the family estate -- litigation that introduced reams of medical
records detailing Fred Trump Sr.'s condition.
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The former senior executive at the Trump Organization recalled Trump
bringing his father to a party in the mid-1990s when it was clear the
elder Trump was suffering from dementia. He said Donald Trump had an
abiding fear of germs and diseases.
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Trump's father died at 93 years old in June 1999, eight years after
the first formal diagnosis of dementia.

https://www.washingtonpost.com/politics/2024/03/20/donald-trump-dementia-father-fred-alzheimers-biden/

Most likely, Fred was failing a number of years before 1985.  IIRC,
Alzheimer can drag on for some twenty years, for some.