Responding to queries on the subject, spokesman Hogan Gidley said simply: "No."
"He's sharp as a tack," Gidley told reporters on board Air Force One.
Trump, 71, will be examined at the Walter Reed military hospital in a Washington suburb Friday and the results are set to be made public.
During the 2016 presidential campaign, Trump published a letter by his long term doctor Harold Bornstein that stated he was in "excellent physical health."
Angered by the publication of a bombshell book that raised doubts over his mental faculties, Trump took to Twitter this weekend to describe himself as "a very stable genius" and "like, really smart.