President Trump insisted on taking a cognitive assessment exam as part of his annual physical last week, and scored a 30/30 on the test, confirming his doctor's belief that he does not show any signs of mental deterioration.

"I had no concerns about the president's cognitive ability," Dr. Ronny Jackson, Trump's in-house doctor who oversaw his physical exam at Walter Reed Medical Center in Bethesda, Md., last week, told reporters on Tuesday.

Jackson said Trump nevertheless requested that he undergo a neurological exam, presumably to combat heightened speculation among his critics about his fitness for office and overall mental health. He said it's the first time any president took this kind of test, as far as he knows.

"He mentally is very sharp, very tact," Jackson told reporters, noting that Trump scored 30 out of of 30 on the Montreal Cognitive Assessment, a test that can help detect mild cognitive impairment or Alzheimer's disease.

[What is the MoCA, the cognitive exam Trump took?]

"The cognitive test, it's well-respected. It's a test that's used throughout the United States," he said. "The fact that the president got 30/30 on that exam, there's no indication whatsoever that he has any cognitive issues."

In a book released earlier this month, several unnamed White House aides said Trump has been known to constantly repeat himself and forget the names of key people in his circle and the West Wing. The passages led critics of the president to suggest he may be unfit for office.

MSNBC's Joe Scarborough, for instance, claimed on air that Trump may be suffering from "dementia." Others suggested he may not have the stamina to spend three more years in office.

But Jackson disputed that narrative on Tuesday, suggesting the president has "incredible genes" and is extremely healthy despite having no regular exercise regime or diet.

"All clinical data indicates that [Trump] is currently very healthy, and that he will remain so for the duration of his presidency," he said.