As Hillary Clinton's competency is questioned in many quarters following her stumble in New York...
A letter from Hillary Clinton's physician released in July might have described the Democratic nominee as in "excellent health" and "fit to serve" but that hasn't stopped unsubstantiated internet theories surrounding her wellbeing (or supposed lack thereof) following a blood clot in 2012 from gathering momentum and her Republican opponent Donald Trump using these doubts as a stick to beat her with on the campaign trail.
Just last month in Ohio, Trump declared Clinton – two years his junior – to be lacking "the mental and physical stamina to take on Isis and all of the many adversaries we face."
A coughing fit in Cleveland and a diagnosis of pneumonia after "overheating" at a 9/11 memorial in New York have only added fuel to the fire.
While Trump was relatively restrained on Fox News today, hoping she gets well and back on the trail, by announcing he would release the results of his own physical later this week, he was once again attempting to contrast his own apparent virility and haleness against Clinton.
It's an important question for American voters, who would clearly rather have someone in full health in the White House for at least the first four-year term.
Not that that ideal situation has always played out. Indeed, the very first US President was plagued with ailments and some of the most iconic commanders-in-chief have had their own grave issues of their own to conquer.
And then there have been those who sadly passed away in office, not due to a bullet, but natural causes.
Here are just seven examples from across the 238-year history of the United States of America of the varying degrees health has impacted the POTUS...
The inaugural president of the United States is had more to battle in life than just the British.
As author Peter Henriques put it, "Washington died exceedingly hard" two years after he left office.
His cause of death at the age of 67 was a throat infection called epiglottitis but that was just one of the maladies that marked his time on Earth.
As a teen, he suffered from diphtheria. He also had tuberculosis at a time when a doctor's prescription for it would often consist of "breathing in fresh air". Small pox followed before he was in his twenties.
As a soldier, dysentery and malaria cropped up. Then later in life, you can add "quinsy" (old school tonsillitis), pneumonia and, to top it all off, he had a carbuncle on his face that was thought by some to be cancerous. It's remarkable he lasted as long as he did.
The ninth US President didn't fare so well, becoming the first POTUS to pass away on the job.
At 68 years of age, he was the oldest president to take office until Ronald Reagan over two centuries later.
His malnourished appearance and strict diet predominantly consisting of dairy products was attributed to stomach ulcers.
Harrison's ultimate undoing came as a result of a two-hour inaugural speech delivered outdoors in harsh March conditions.
Having caught a cold, he was seriously ill with right lower lobe pneumonia and "congestion of the liver" by late March. He died on April 4th, a mere month into his presidency and the shortest tenure on record.
Less than a decade after Harrison's sudden passing, another incumbent president left this mortal coil.
The Virginian lasted little more than a year in office before he died aged 65, most likely from cholera (though there has been plenty of speculation around that).
He told a medical attendant the day before he died:
"I should not be surprised if this were to terminate in my death. I did not expect to encounter what has beset me since my elevation to the Presidency. God knows I have endeavoured to fulfill what I conceived to be an honest duty. But I have been mistaken. My motives have been misconstrued, and my feelings most grossly outraged."
Widely regarded to be the greatest US president of all time, Abraham Lincoln, of course, lost his life through assassination, but when he was alive, he wasn't particularly well.
There is a theory that Lincoln suffered from a genetic disorder known as Marfan syndrome. His ancestors have also wondered whether his famously clumsy gait could have come from the incurable hereditary disease ataxia.
Not only did Lincoln not let his health get in the way of his mission to abolish slavery, his imposing 6'4" stature - which gave him the upperhand over many of his political opponents - could actually have been caused by Marfan syndrome.
While not quite hitting Washington's levels of ill-health, Lincoln also had smallpox to deal with, having come down with it shortly after delivering the Gettysburg Address.
The man who was at America's helm during the Second World War was also hiding the fact he had to rely heavily on a wheelchair when he entered the White House and went on to win a record three further elections despite tht fact.
In fact, the Democrat's political dominance led directly to today's two-term limit being put in place.
Roosevelt was hit with polio when he was holidaying with his family on Campobello Island in 1921, and left paralysed from the waist down, aged just 39.
He eventually succeeded in teaching himself to walk short distances again whilst wearing iron braces on his hips and legs, and managed to conceal the extent of his disability, despite the fact his illness had been well-known.
Despite winning a fourth term in 1944, Roosevelt's health was rapidly declining by that point. He eventually suffered a cerebral hemorrhage and died on April 12th, 1945.
Considering his campaign was run, and perhaps won, on his apparent youthful energy when compared to his 1960 presidential opponent Richard Nixon, it would have surprised many to learn that John F Kennedy was in very poor health before his assassination at the age of 46.
As far back as 1960, Lyndon B Johnson's aides had told the press that JFK had Addison's disease and that it was life-threatening.
Despite the Democratic camp denying the allegations, the subsequent release of his medical records shows that their accusations were correct.
Kennedy did indeed suffer from this adrenal gland condition, which causes a deficiency of the hormones needed to regulate blood sugar, sodium, potassium and the stress response.
Kennedy had been a sickly child and spent periods of his school and college years in hospital for infections and intestinal ailments.
Alongside Addison's disease, he suffered from ulcers, colitis and degenerative back trouble.
It meant that during major events such as the Bay of Pigs and the Cuban missile crisis, JFK was on a startling cocktail of medications, including steroids, anti-spasmodics, antibiotics, antihistamines and painkillers.
He was also on an anti-psychotic for two days on at least one occasion and had the notorious German physician Max Jacobson, known as "Dr Feelgood", among his medical staff.
At 69, the Gipper became the oldest incoming US president to date in 1981.
Due to concerns regarding his age during his first campaign for office, Reagan had vowed to resign if he became medically unfit.
He survived a shooting in the first month of his presidency and went on to be a political powerhouse for the rest of the decade, but there was always a question mark over his constitution,
It has been speculated he suffered hearing loss as a result of the incident, eventually leading to the use of hearing aids.
More seriously, in 1985, he transferred his power to Vice President Bush for less than eight hours when he underwent surgery for colon cancer.
He then underwent transurethral prostate surgery in 1987.
Soviet foreign minister Andrei Gromyko would later comment:
"The Cold War began to end when two elderly gentlemen discovered that they shared a common difficulty with their bladders."
While the fact Reagan was suffering from Alzheimer's disease was not made public until 1994, there has been much speculation over whether he had it while in office.
Certainly there had been many instances where Reagan had seemed forgetful. A study published in the Journal of Alzheimer's Disease also showed he used significantly fewer unique in the latter years of his presidency.