Hillary Clinton suffered a medical episode Sunday that her doctor now says was pneumonia while attending a ceremony in New York marking the Sept. 11, 2001, terrorist attacks. It was sufficiently serious that aides and secret-service agents had to hold her upright, save her from falling and bodily lift her into an armoured van while attempting to keep her out of view.

While Ms. Clinton, the Democratic nominee for president, later tried to brush off her near-collapse as nothing more than feeling a little “overheated,” it raised new, serious concerns about her fitness – at the age of 68 – to serve a four-year presidential term.

Long-dogged by doubts about her health, Ms. Clinton shifts between insisting she is fit, vigorous and fully capable of coping with the stresses of being commander-in-chief and citing brain injury as an excuse for failing to remember crucial briefings about handling classified e-mails.

Ms. Clinton has cancelled a trip to California planned for Monday and Tuesday, her campaign said late Sunday.

Ms. Clinton was attending a solemn 15th-anniversary event at Ground Zero marking the attacks that destroyed New York’s twin towers when she was abruptly taken ill about 9:30 a.m. “During the ceremony, she felt overheated so departed to go to her daughter’s apartment, and is feeling much better,” her campaign said in a statement issued two hours later.

Late Sunday afternoon, the campaign announced that Ms. Clinton had been diagnosed on Friday with pneumonia. It provided no explanation for delaying that announcement. “On Friday, during follow-up evaluation of her prolonged cough, she was diagnosed with pneumonia,” her physician Lisa Bardack said. “She was put on antibiotics, and advised to rest and modify her schedule.”

Video of the incident suggested a far more serious event. Ms. Clinton, held up by aides and leaning for support against a concrete pylon, suddenly lurched forward, stumbled and was prevented from falling only because a burly security man caught her arm. Then she was half-carried, half-lifted into a black van, apparently losing one shoe as it was dragged along the sidewalk. The official pool of reporters designated by the campaign to travel with Ms. Clinton was left behind.

Ms. Clinton made a brief appearance later on Sunday. “I’m feeling great,” she said, on the sidewalk outside daughter Chelsea’s apartment. “It’s a beautiful day in New York.”

Donald Trump, the Republican presidential nominee, has taunted Ms. Clinton repeatedly, suggesting she lacks the strength to be president and is hiding significant illness from American voters. “I think that both candidates, Crooked Hillary and myself, should release detailed medical records. I have no problem in doing so!” he tweeted in a typical goading message earlier in the campaign.

Dr. Bardack, chair of internal medicine at Mount Kisco Medical Group, has said Ms. Clinton “is in excellent physical condition and fit to serve as President of the United States.”

Surrogates for Mr. Trump have been even more direct in accusing Ms. Clinton of suffering from serious neurological problems.

There are “reports or observations of Hillary Clinton’s behaviour or mannerisms … as well as her dysphasia,” Katrina Pierson said last month, referring to a brain disorder caused by trauma that damages the ability to speak or comprehend speech. “She’s fallen, she has had a concussion, there are really interesting things out there,” Ms. Pierson said, referring to apparently fraudulent medical reports circulating in cyberspace and attributed to Ms. Clinton’s physician.

Dr. Bardack came to Ms. Clinton’s defence. “These documents are false, were not written by me and are not based on any medical facts,” she said after the Trump campaign floated the dysphasia report.

Still, Ms. Clinton did suffer a serious concussion in December, 2012, when she was secretary of state. She fainted and fell at home, striking her head on a table. While officials minimized the seriousness of the injury at the time, Ms. Clinton, when she returned to work, was limited to two days a week. Two years later, her husband, former president Bill Clinton, revealed the concussion was so serious it “required six months of very serious work to get over.”

And as recently as this summer, Ms. Clinton blamed the concussion – while being questioned by the Federal Bureau of Investigation into her mishandling of classified e-mails on a private server in the basement of her Chappaqua, N.Y., residence – as the reason she couldn’t recall the details of some briefings about the issue.

Dogged by a persistent whispering campaign about brain damage and her stamina in general, Ms. Clinton occasionally seeks to make light of the attacks.

“The National Enquirer said I would be dead in six months. So with every breath I take, I feel like I have a new lease on life,” she told comedian Jimmy Kimmel. She blamed the Trump campaign for the scurrilous attack. “It’s part of the wacky strategy – just say all these crazy things and maybe you can get some people to believe you.”

She also said she had no reason to doubt Mr. Trump’s health. “I mean, as far as I can tell, he’s as healthy as a horse,” she said.

Recent presidents have been generally far fitter than the average American and a generation younger than either Ms. Clinton or Mr. Trump.

Bill Clinton was 46 when he became the second-youngest president ever elected. George W. Bush was 54 but so fit that his daily mountain biking jaunts left some of his Secret Service detail panting. Barack Obama was inaugurated at 47. Although he has given up basketball for golf, he still spends a gruelling 90 minutes daily in the gym.

Average age for a president on taking office is just under 55 years. Ronald Reagan, who became president days before his 70th birthday, was the oldest person ever elected president and the oldest still serving the Oval Office when his second term ended eight years later. But his detractors have suggested that the Alzheimer’s disease that would eventually kill him, had started to affect his cognitive functions while he was still in the Oval Office.

Mr. Trump, 70, if elected, would eclipse Mr. Reagan as the oldest-ever-elected president.

Ms. Clinton would be 69 on inauguration day, only a few months younger than Mr. Reagan.

So far, neither health nor age has played a major role in the campaign, largely because the Republican front-runner and both Democratic candidates in the primaries were three of the oldest people ever to seek the presidency. (Vermont Senator Bernie Sanders is 75.)

But at least some medical experts think age matters – a lot.

“We should probably assume that a significant proportion of political leaders over the age of 65 have impairment of executive function,” Mark Fisher, a professor of neurology and political science at the University of California, wrote in a published paper last year.

“These are the complex cognitive processes that guide ‘normal decision-making.’ The onset of these changes can be sudden, as in a stroke, or slower, as a result of microbleeds or routine, age-related changes to brain structure.”

WASHINGTON — The Globe and Mail
Published Sunday, Sep. 11, 2016 11:34AM EDT
Last updated Monday, Sep. 12, 2016 7:03AM EDT