from the NYT:

…even with the hindsight of Mr. Reagan’s [Alzheimer’s] diagnosis, his four main White House doctors say they never detected any evidence that his forgetfulness was more than just that. His mental competence in office, they said in a series of recent interviews, was never in doubt. Indeed, they pointed out, tests of his mental status did not begin to show evidence of the disease until the summer of 1993, more than four years after he left the White House.

“There was never anything that would raise a question about his ability to function as President,” said Dr. Lawrence C. Mohr, one of Mr. Reagan’s physicians in his second term. “Ronald Reagan’s cognitive function, belief structure, judgment, ability to choose between options, behavior and ability to communicate were totally and completely intact.”

[…]

He “never forgot appointments, misplaced or lost things, where he put his glasses, never forgot to put his hearing aids in, never forgot to put his contact lenses in, and these are things he did for himself,” Dr. Mohr said. “I saw him saddle and bridle horses at the ranch and later put things back exactly where they belonged.” And Mr. Reagan, the doctors stressed, was punctual, never depressed and had no difficulty with language or understanding what was going on around him.

From Snopes:

Although no cognitive tests were administered to Reagan during his time in office (his doctors saw no need for them), he did begin receiving annual mental and psychological assessments in 1990, after undergoing surgery to remove a blood clot in his brain. The four-hour battery of tests, which would have detected signs of dementia, found nothing amiss for the first three years they were administered. “All parameters for his age absolutely were within the normal range,” one of Reagan’s doctors said. It was Reagan himself who announced the diagnosis of Alzheimer’s in 1994.

There were certainly no indications of dementia (age, perhaps, but not dementia) when the 81-year-old former president delivered a 35-minute speech at the 1992 Republican National Convention, a performance Washington Post reporter Bob Woodward described as “flawless.”


It must also be said that given that the average life expectancy of a patient diagnosed with Alzheimer’s Disease is eight to 10 years, Reagan, who died in 2004 (10 years after his diagnosis), would have been extraordinarily long-lived for an Alzheimer’s patient if he was already suffering from the disease, as some claim, in 1984.