But the research does suggest that alterations in speech one day might be used to predict development of Alzheimer’s and other neurological conditions years before symptoms are clinically perceptible.

Detection of dementia at the earliest stages has become a high priority. Many experts now believe that yet-to-be-developed treatments are likely to be effective at preventing or slowing progression of dementia only if it is found before it significantly damages the brain.

The “highly innovative” methods used by the researchers may eventually help “to further clarify the extent to which spoken-word changes are associated with normal aging or predictive of subsequent progression to the clinical stages of Alzheimer’s disease,” said Dr. Eric Reiman, the director of the Banner Alzheimer’s Institute in Phoenix, who was not involved in the new study.

Visar Berisha and Julie Liss, professors of speech and hearing science at the university, compared transcripts of all 46 news conferences that Mr. Reagan held to the 101 sessions President George H. W. Bush held in his term.

The researchers assessed changes in the presidents’ speech patterns with a new algorithm based on a technique used by others to analyze changes in writing by novelists.