Biden's aides said his debate performance was poor because he struggles to function after 4 p.m.: report

• Biden's aides defended his debate performance, citing his limited optimal hours, Axios said.
• Biden performs best between 10 a.m. and 4 p.m., aides told the publication.
• Some blamed his poor performance on over-preparation by aides, according to the Washington Post.

Joe Biden's aides have defended his poor debate performance, saying he struggles to function outside a six-hour window during the day, according to Axios.

The publication, citing people close to the president, said Biden works best between 10 a.m. and 4 p.m.

According to the anonymous aides, who spoke to Axios, Biden is more likely to make verbal mistakes and become tired outside this time period or while traveling abroad.

Business Insider could not independently verify the comments.

Biden's aides have also come under fire. According to the Washington Post, some in Biden's inner circle blamed his poor performance on over-preparation.

Others said that too many aides were involved in his weeklong preparations at Camp David, according to the report.

Biden and Trump went head-to-head in their first debate of the year on Thursday at 9 p.m. ET in Atlanta.

Commentators and politicians deemed the debate disastrous for Biden and questioned whether he was too old for another term as president.

During parts of the debate, Biden, 81, made confusing statements and appeared to forget what he was saying mid-sentence. For example, when asked about the national debt, Biden stumbled and said, "We finally beat Medicare."

"I spent half my career being criticized for being the youngest person in politics. I was the second youngest person ever elected in the United States Senate — and now I'm the oldest," Biden said when asked to address concerns about his age during the debate.

His aides' comments seem to contradict Biden's own argument that age shouldn't be a factor in the presidential race.

"My fellow Americans, the issue facing our nation isn't how old we are: It's about how old our ideas are," he said during the State of the Union address in March.

"You can't lead with ancient ideas that only take us back," he added.

He made a similar point during an interview with MSNBC host Stephanie Ruhle in May.

"I have acquired a hell of a lot of wisdom and know more than the vast majority of people," he said. "And I'm more experienced than anybody that's ever run for the office. And I think I've proven myself to be honorable as well as also effective."

Biden admitted he performed poorly, but downplayed its importance.

"I don't walk as easy as I used to, I don't speak as smoothly as I used to, I don't debate as well as I used to," he said to the crowd in Raleigh, NC.

"I know how to tell the truth. I know right from wrong. And I know how to do this job, I know how to get things done," he added.

Representatives for the Biden campaign did not immediately respond to a request for comment.