Trump has refused to release any medical records heading into next month's election, even though he would be, were he to win, the oldest president to take the oath of office. On Sunday, at a campaign event in Pennsylvania, he denied being close to 80 years old or having any cognitive issues.

"I'm not 80, and I'm not that close to 80," said Trump, who is 20 months away from turning 80. "I've done cognitive tests. I've done them twice, and I aced both of them, and the doctor in one case said, I've never seen anybody ace them.'"

Dyer and other psychiatrists, though, said that test, often used as an initial screening tool which Trump took nearly seven years ago, is not helpful in assessing his current condition.

"That assessment is given to potential nursing home patients to decide which wing to assign them to, not to someone you want to hire, let alone be president," said Andrew Smolar, a Pennsylvania psychiatrist who has had numerous patients of Trump's age and apparent condition.