As Trump turns 80, what's it really like to work as an octogenarian?

While being older often means being more experienced at one's job, some think it can be a liability if serious age-related illnesses - like cognitive decline and general loss of stamina - get in the way.

The issue of ageing is what eventually led Biden to drop his re-election bid in the presidential race against Trump in 2024. After a dismal debate performance, prominent Democrats raised worries about Biden's cognitive abilities and called on him to leave the race.

Some lawmakers and members of the public have also raised concerns about Trump's health as he turns 80.

At a congressional hearing this month, Democrat Ted Lieu showed a series of videos which appeared to show the commander-in-chief dozing off in meetings, saying it showed "something very wrong".

Secretary of State Marco Rubio called the line of questioning "absurd" and said he had never seen Trump fall asleep in public. "On the contrary, the guy doesn't sleep, which is a big problem."

Trump's physician has said the bruising regularly seen on the president's hands is down to "minor soft tissue ‌irritation related ⁠to frequent handshaking in the setting of aspirin use for cardiovascular prevention".

After a medical exam two weeks ago at the Walter Reed National Military Medical Center, Trump's doctor said the president was in "excellent health".

Capt Sean Barbabella went on to say that the president's "demanding daily schedule, including multiple high-level meetings, public engagements and regular physical activity continues to support his overall well-being".

But rest can be critical for an older person working in a stressful environment.

The effect of life stressors - such as sleepless nights - can actually be detected in cellular activity, Lithgow said.

"It's actually real biological stress, and it accelerates ageing," he said. "Chronic stressors daily can have a really ravaging effect on people."

Lithgow said sleep was one of the most important factors, as it turns on molecular processes that initiate repairing and recovery in the body.

Cohen said one of her secrets to longevity is sleeping more than eight hours a night, as well as being an avid reader and conversationalist. Her family has always worked past retirement age, including her grandmother, who died while in her 80s in a hallway of the building she owned on her way to fix the plumbing in a tenant's apartment.

"I always knew I would work forever," she said, adding that her work has allowed her to be generous with her family and travel when she wants.

Cohen's career in law - including the new firm she founded with her daughter at age 88 - has given her a sense of purpose, which Lithgow said can often be a benefit for people working in their later years.

That purpose is what drove Rose to keep practising medicine for so long. What he loved most about his job was seeing patients, some of whom started coming to him when they were teenagers and stayed well into their adult years.

"They were still coming to see me 50 years later, which shows you what a bad job I did," he joked.

Rose said the thought never occurred to him to retire earlier because he liked what he was doing, and because he felt like his patients and society were relying on him as a physician.

"I guess I felt that no one could do without me," he said.

Besides a sense of purpose, Lithgow said other factors that can help guard against ageing are good diet, exercise and rest.

But the strongest protectors against accelerated ageing, he said, are a person's income and availability of resources, including health care. Genetics, meanwhile, don't play too much of a role.

"If you start with an ability to access the best possible healthcare, then you're already having an advantage over the vast majority of people," Lithgow said.

Rose remains in good health at the age of 95, though he does not know what sets him apart from many of his peers who never made it to that age, let alone practising medicine.

"I really haven't the faintest idea as to what I've done," he said. "I don't smoke. I have a schnapps every now and then."

Rose said his patients for the most part did not know how old he was, or they did not seem to care. But some were shocked to find out about the 95-year-old doctor.

"The reason is I haven't aged," he said. "I don't look any different."