The ?? ?? ??revelation of Hillary Clinton's pneumonia diagnosis over the weekend, coupled with the images of her stumbling while leaving a Sept. 11 memorial event, has fueled critics who have long called on the Democratic nominee for president to release her health records.

Clinton's diagnosis has brightened the spotlight on presidential candidates' medical records, one with a short history of transparency and a long history of controversy.

Historical precedence

Historically speaking, there's been little consistency regarding the release of a presidential candidate's health records. In fact, there's no requirement to release those records. It's done voluntarily by campaigns to prove to voters the health and vitality of the men and women who seek to serve. The public demand follows decades of deception as candidates routinely hid their true conditions (more on that in a bit).

But in the long history of the race for the White House, going back nearly 230 years, it's only since the 1980s that health records have become an issue with candidates, as the New York Timesnoted in a recent piece about both Trump and Clinton's reluctance on the issue.

Republican candidates including Bob Dole, both George H.W. and George W. Bush, and Mitt Romney have been fairly transparent with health records and treatment, most notably Sen. John McCain, who answered questions about his health in 2008 by dropping around 1,100 pages of information.

For Democrats, Al Gore and John Kerry were open about their own health records, though both Bill Clinton and Barack Obama were more reluctant.

The diseased, depressed and drunk

While there's an understandable skepticism around the allegations of Clinton's health given the source (predominantly vocal online members of the alt-right), many of those making accusations against Clinton cite previous examples of candidates concealing ailments.

Woodrow Wilson had suffered multiple strokes by the time he first ran for president in 1912 and the danger of future ailments caught up with him in October 1919 in the form of a massive stroke that left him debilitated. The country, though, never knew; his wife Edith called the shots while Wilson, who would never fully recover, was incapacitated.

Franklin Roosevelt, who had battled polio before being elected in 1932, was elected to his unprecedented fourth term in 1944 despite extremely poor health that left his inner circle doubtful he would live out the term.

And perhaps most famously, John F. Kennedy hid the numerous ailments he suffered from when he ran for president in 1960, which included gastrointestinal issues, severe back problems, and Addison's disease, all of which required a battery of drugs and steroids.

The question of health in a campaign has also extended beyond the presidential candidate. In 1972, George McGovern's campaign suffered a blow when his running mate, Thomas Eagleton, was booted from the campaign after it was discovered he had undergone electroshock therapy to help deal with depression in the 1960s.

A fuller context

Yet, these examples are the most extreme and, in a fuller, historical context, it's difficult to find a president that didn'thave some kind of ailment or issue either before or after he reached office.

Franklin Pierce, Ulysses S. Grant, and, more recently, George W. Bush all had issues with alcohol. Both Pierce and Calvin Coolidge were said to have suffered from PTSD-like symptoms after the untimely deaths of children. And a 2006 study in the Journal of Medicine and Philosophy showed that 18 of the 37 presidents, from Washington through Nixon, "met criteria suggesting psychiatric disorder."

There remains a stigma connected to a candidate's health if they're running for the highest office in the land despite the fact that medical advancements have made both diagnosing and treating medical issues far easier.

It's also worth noting that these issues that affected past presidents are far more serious than a treatable illness like pneumonia. There's also no evidence of anything more serious plaguing Clinton.

Trump's health

As far as this race goes, it's not as if Clinton's opponent has been necessarily forthcoming about his own health. Donald Trump is purportedly in "perfect" health (despite a penchant for fried fast food) but questions around Trump's peculiar doctor have resulted in ongoing skepticism.

On Monday, Trump said he'd release "very, very specific numbers" from a recent physical but will do so on the Dr. Oz show rather than release records straight to the public.

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As for Clinton, she promised on Monday to release additional information about her health and family history in the wake of the pneumonia diagnosis.

Last summer, as she kicked off her campaign, Clinton released a letter from her doctor outlining her health in light of a series of incidents, including her 2012 concussion that resulted from a fainting spell caused by dehydration related to a stomach virus.

Leave it to Ben Carson to be hilariously blunt about the whole thing. In August, Carson, in calling on both candidates to be transparent about their health, referred to both as "elderly" (Clinton is 68, Trump is 70).

"My diagnosis would be that anybody who is elderly should expose their records, and we the people should know what they are, because it's a very stressful job. It's not an eight-hour a day job, it's 24/7, and we need to make sure that that is taken care of," he said.

It's worth noting, then, that on Jan. 20, 2017, Inauguration Day, Clinton will be 68 years and 86 days old, the second oldest president at inauguration (behind Reagan) while Donald Trump will be 70 years and 220 days old, which would be the oldest president ever upon entering office.