Ronald Reagan's son thinks his father's Alzheimer's disease began while he was president, he writes in a new memoir. In "My Father at 100," which is being released Tuesday, Ron Reagan says he saw evidence that his father was losing his mental edge in his first term, Politico reports.

"Today, we are aware that the physiological and neurological changes associated with Alzheimer's can be in evidence years, even decades, before identifiable symptoms arise," the younger Reagan wrote. "The question ... of whether my father suffered from the beginning stages of Alzheimer's while in office more or less answers itself."

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