Democratic presidential candidate Joe Biden, 77, has said that he was being “constantly tested” for cognitive abilities but his campaign declined to release the results, according to The Federalist.

Biden has faced questions about his cognitive capabilities throughout his campaign given the former vice president’s well-documented history of being confused, gaffes, and misstatements. 

“I’ve been tested and I’m constantly tested,” Biden said during a press conference Tuesday. “All I gotta do is watch me, and I can hardly wait to compare my cognitive capability to the cognitive capability of the man I’m running against.”

However, Biden’s statement raised eyebrows as he said he’s “constantly tested,” prompting President Donald Trump to challenge him to take a cognitive test on Friday.

“He cannot pass the test I ‘aced,’” the president tweeted. “He should give it a try!!!”

President Trump already took a cognitive test in 2018 in which he passed with a perfect score. The result was confirmed by retired Rear Adm. Ronny Jackson, who was White House physician during the Barack Obama and Donald Trump administrations. 

“The President didn’t have anything to hide,” Jackson told ‘The Kyle Olson Show’ on Friday, reported Breitbart News. “I knew he was cognitively intact.”

Jackson said he’s not diagnosing Biden and has not examined him but believed the former vice president has “got some cognitive issues.”

“But as a concerned American who also happens to be a physician, I’m just going to say it’s concerning to me that he sometimes is not able to complete a sentence, not really know where he’s at or what he’s doing, and we’ve seen that countless times now,” Jackson said. “It doesn’t take a neurosurgeon, it doesn’t take a psychiatrist to realize that Joe Biden does not possess the mental acuity right now to lead this country.” 

Jackson said the Biden campaign cannot afford to put him “on the stage side-by-side with President Trump” and it won’t let him take the test “because it’s not going to be good for him.”

Nearly 40% of likely voters, including 20% of Democrats and 30% of Independents likely to vote, believe the former vice president is suffering from dementia, according to a poll published Monday by Rasmussen.