Lawrence Altman, "Parsing Ronald Reagan’s Words for Early Signs of Alzheimer’s", NYT 3/30/2015:
Even before Ronald Reagan became the oldest elected president, his mental state was a political issue. His adversaries often suggested his penchant for contradictory statements, forgetting names and seeming absent-mindedness could be linked to dementia.
In 1980, Mr. Reagan told me that he would resign the presidency if White House doctors found him mentally unfit. Years later, those doctors and key aides told me they had not detected any changes in his mental abilities while in office.
Now a clever new analysis has found that during his two terms in office, subtle changes in Mr. Reagan’s speaking patterns linked to the onset of dementia were apparent years before doctors diagnosed his Alzheimer’s disease in 1994.