Two-thirds of American voters are worried about Hillary Clinton's health and agree with Donald Trump's suggestions that she has a lack of 'stamina,' a new poll suggests.

An Associated Press-GfK poll found that voters, especially men, have more confidence in Trump's health than Clinton's.

The result comes despite the Clinton campaign's attempts to calm the public fears that increased after she was diagnosed with pneumonia and had a public collapse on Sept. 11.

She has released about the same amount of medical information as Trump, and independent doctors who have looked at the available data say both candidates seem fine.

Two thirds of voters are worried about Hillary Clinton's health and agree with Donald Trump's statements that she has a lack of 'stamina', a new poll suggests. She is pictured during Monday night's presidential debate

Clinton went 95 minutes without coughing on Monday night but it resurfaced in a brief conversation on Tuesday morning on her campaign plane

But Wednesday's survey shows evidence of the political points Trump scored after her much-publicized pneumonia, which caused her to drop out of the campaign for several days after her collapse at a 9/11 memorial service in New York.

The AP-GfK poll found 51 per cent of voters were very or extremely confident that the 70-year-old Trump is healthy enough to be president.

But only 36 per cent had the same confidence in the health of Hillary, who turns 69 a few days before the November 8 election.

Nearly half of women, but only four in 10 men, thought her health was getting too much attention, according to the poll, which was taken before the presidential candidates' debate on Monday.

Concerns about her health increased when she was spotted collapsing into a van after her Secret Service detail rushed her away from the September 11 memorial service. Her doctor later said she had pneumonia

Trump (pictured, at a rally in Melbourne, Florida, yesterday) is 18 months older than Clinton but voters have more confidence in his health

'Everybody gets sick,' said Sherri Smart, 56, of New York.

She said she had not decided who to vote for but wished the candidates would discuss issues instead of sniping about who's most vigorous.

'What's important is, what are you going to do for me?' said Ms Smart.

The former Secretary of State told the debate at Hofstra University there were no doubts about her stamina and she pointed out she had visited 112 countries during her time in office and once testified for 11 hours before a congressional committee.

But Trump said: 'She doesn't have the look. She doesn't have the stamina, I said she doesn't have the stamina, and I don't believe she does have the stamina.'

Hillary Clinton has at times looked unwell during the campaign although she seems to have recovered well from her bout of pneumonia

According to the poll men were more likely to question Clinton's physical fitness for the job, with 45 per cent saying they were only slightly or not at all confident compared to 34 per cent of women.

More Democrats were confident of Trump's health than Republicans were of Clinton's.

'Stamina is a code word for maybe not physically up to the job,' said New York University bioethicist Arthur Caplan, who has called for an independent panel to certify the health of presidential candidates.

'There's something of a bias about men versus women that subtly Trump has played to, that men are more fit, tough enough to do the job,' said Mr Caplan.

Health is a legitimate issue as the nation is poised to elect one of its oldest presidents.

Both are 'baby boomers', born in the years just after the Second World War, but although Trump is 18 months older there have been more doubts about Clinton's health.

In 1960 a tanned and healthy-looking John F. Kennedy was considered to have won the TV debate against Richard Nixon, who was perceived as looking unwell.

Kennedy won the election, although only after his death at the hand of an assassin's bullet was it revealed that he suffered from Addison’s disease or autoimmune polyendocrine syndrome type 2, an illness which can result in such as fatigue, dizziness, muscle weakness, weight loss, nausea, sweating, and changes in mood and personality.

Clinton took a firm grip of the rail as she climbed the steps to her campaign's Boeing 737 at White Plains Airport, near her Chappaqua, NY, home

Donald Trump and Hillary Clinton spar during the presidential debate at Hofstra University

Clinton had kept her pneumonia diagnosis secret until a public stumble on September 11 forced her to reveal the truth, suggesting her campaign staff feared the impact it might have on voters.

Neither candidate has released their full medical records, preferring summaries from their personal physicians which left no way of knowing if anything important had been left out.

But the AP-GfK poll found nearly four in 10 voters do not consider such a release important, and another 20 per cent said it was only moderately important.

Trump's gastroenterologist released a four-paragraph letter in December saying the GOP nominee would be 'the healthiest individual ever elected'.

Earlier this month Trump told The Dr Oz Show he felt great, and also released details about his cholesterol levels and cancer screenings.

Trump takes a cholesterol-lowering statin medication and a baby aspirin, has some mild plaque in his arteries and is overweight, according to the data, but was declared generally in good health.

Last summer Clinton released a two-page letter detailing her family history, prior exams including lab test results, and some prior ailments that have healed — including a 2012 concussion and blood clot she suffered after becoming dehydrated from a stomach virus and fainting.

Republican presidential nominee Donald Trump answers a question during the presidential debate at Hofstra University in Hempstead, New York

This month a second letter outlined the mild pneumonia and revealed some updated check-up results.

So we know she takes a blood thinner as a precaution given a history of blood clots, as well as a thyroid medication and allergy relievers but also was declared generally in good health.

Some doctors say just watching how the candidates handle a physically demanding campaign trail and the cognitive finesse needed to debate can give voters a good idea of health.

But while the public may not pay attention to cholesterol tests and EKGs, it was hard to miss that image of Clinton stumbling.