Ronald Reagan's son: Alzheimer's seen during presidency

Former President Ronald Reagan is pictured waving to well-wishers on the south lawn of the White House on April 25, 1986.

WASHINGTON (Reuters) - Former President Ronald Reagan, who was diagnosed with Alzheimer's disease five years after leaving office, showed signs of the condition while still in the White House, his son says in a new memoir.

In the book, "My Father at 100, a Memoir," Ron Reagan writes he had an inkling of trouble three years into his father's first term.

Later, watching his father debate 1984 Democratic presidential nominee Walter Mondale, "I began to experience the nausea of a bad dream coming true," Ron Reagan wrote.

"Some voters were beginning to imagine grandpa -- who can never find his reading glasses -- in charge of a bristling nuclear arsenal, and it was making them nervous," said Ron Reagan, according to a published excerpt of his book.

"Worse, my father now seemed to be giving them legitimate reason for concern. My heart sank as he floundered his way through his responses, fumbling with his notes, uncharacteristically lost for words. He looked tired and bewildered."

Reagan was diagnosed in 1994 with Alzheimer's, an incurable, brain-wasting disease, and died 10 years later. Ron Reagan's book will be published on Tuesday, ahead of the 100th anniversary of his father's birth on February 6.

Ron Reagan, the youngest of the former president's four children, said he believed his father was probably not surprised to be diagnosed with the disease.

"As far back as August 1986 he had been alarmed to discover, while flying over the familiar canyons north of Los Angeles, that he could no longer summon their names," Ron Reagan said in the memoir.

The Ronald Reagan Presidential Foundation denied that Reagan showed signs of the illness while he was president.

"This subject has been well documented over the years by both President Reagan's personal physicians, physicians who treated him after the diagnosis, as well as those who worked closely with him daily," the foundation said in a statement.

"All are consistent in their view that signs of Alzheimer's did not appear until well after President Reagan left the White House," the statement said.

(Editing by Peter Cooney)