First lady Jill Biden has dismissed speculation about president Joe Biden’s mental health as “ridiculous”.

In an interview with CBS Morning, the first lady opened up about polls questioning her husband’s mental fitness as well as adjusting to life in the White House.

Portions of the interview by CBS’ Rita Braver were released on Thursday.

In the interview, Ms Braver referred to recent polls that concluded Mr Biden was not mentally fit to be president.

A survey conducted by Politico-Morning Consult last month revealed that 48 per cent of those surveyed believed the president was not “mentally fit”, while 49 per cent said he was.

“Quite a few Americans have some questions about the president’s current mental fitness,” said Ms Braver in the interview.

At 79, Mr Biden is the oldest president in US history. He has also been subject to social media memes and criticism from political opponents who have consistently suggested that he is mentally unfit to hold office.

“I think that’s ridiculous,” responded Ms Biden, 70, while shaking her head.

Ms Biden also spoke about adjusting to life in the White House as first lady, even though she worked closely there for eight years when Mr Biden was vice president. Ms Biden worked with former first lady Michelle Obama and with military families at the time.

“It’s a little harder than I imagined,” she said, adding that she was taken by surprise by the continuous nature of work in the White House.

“It’s not like a job that you do, it’s a lifestyle that you live. It’s not something you leave at 5:00 or at 3:00. And it’s 24 hours a day,” she further said.

Ms Biden married the president in 1977 when Mr Biden was already a US senator from Delaware.

She has also campaigned for him and with him in successive Senate election bids as well as three bids for presidency.

Ms Biden, who is a professor at North Virginia Community College, has long advocated for free tuition and responded to concerns over the dropping of a proposal for free community college from a major social welfare bill.

However, she said she understood why her husband cut the proposal that he has been trying to get Congress to pass.

“No, I understand compromise,” she said.

In October, Mr Biden said during a CNN Townhall that free community college would not be a part of the final draft of the Build Back Better bill that includes sweeping economic and social welfare expenditures.

Mr Biden, who has long been an advocate of the proposal to expand educational opportunity to all Americans said that the fight was not over.

“I promise you — I guarantee you — we’re going to get free community college in the next several years and across the board,” he said.

In the interview with CBS, Ms Biden echoed her husband and said, “I knew this was not the right moment for it.”

“But that doesn’t mean it might not get passed somewhere down the future,” she added.