Some critics have questioned Hillary Clinton's fitness to be president of the U.S. because she came down with pneumonia. You gotta be kidding! If a common illness like pneumonia made a person unfit to be president, then many American leaders would have never taken office.

U.S. presidents have always had health problems, starting with George Washington himself, who apparently suffered from tuberculosis, malaria, smallpox, dysentery and pneumonia. (Handout/National Portrait Gallery/Reuters) The record starts with George Washington himself. He apparently suffered from tuberculosis, malaria, smallpox, dysentery and pneumonia.

Abraham Lincoln had malaria twice and smallpox. More controversially, there is evidence he also had syphilis. For a long time biographers disputed this. But current medical analysis accepts that he probably did, indeed, suffer from the disease.

Later presidents throughout the centuries plagued by ongoing serious health issues learned how to hide them and, for the most part, got away with it.

Abraham Lincoln shortly after he was elected in 1860, left, and in 1865, just before his assassination. Lincoln had malaria twice and smallpox, and there is evidence he also had syphilis. (Wikipedia Commons) Contemporary bioethicists and medical historians cite some of the deceptions that presidents used to hide their health problems. In 1893, for instance, amid a financial panic, President Grover Cleveland discovered he had a cancerous lesion on his palate. As Americans waited desperately for him to restore economic stability, Cleveland boarded his yacht and had the tumour clandestinely removed as he sailed to his summer home. The crew of the Oneida was sworn to secrecy.

"It would have been catastrophic for him to announce he had cancer," says Dr. Robert Lahita, a researcher and professor of medicine at Rutgers University in New Jersey. "If anything had gone wrong on that boat … it would have been the end of the U.S. as we know it."

The list of presidents who manipulated their health records goes on and on.

Woodrow Wilson suffered a stroke in 1919 that left him incapacitated. His own correspondence showed that he had suffered smaller strokes over the previous two decades but that his wife Edith and his doctor allegedly orchestrated a coverup.

John F. Kennedy declared himself to be "the healthiest candidate for president in the country." Except, of course, for what he kept secret: that he likely had Addison's disease, an autoimmune disorder. He also had osteoporosis and was hospitalized for intestinal and back problems.

All that mystery came to an end in 1967, with the 25th Amendment to the U.S. Constitution to ensure that presidential illnesses were disclosed.

That posed a particularly challenging set of problems for elderly presidents like Ronald Reagan, who was 70 when first elected in 1981. It made him the oldest person ever to serve as president. He was known as the Great Communicator and used his sense humour to cover up both uncomfortable political issues and his growing health problems, particularly his loss of memory.

Former U.S. president Ronald Reagan is shown in his official presidential portrait in 1981, left, and eight years later in his office in October 1989, about nine months after he left the White House. Reagan was one of the longest-living U.S presidents, dying at the age of 93 in 2004. ( The White House / Bob Galbraith, Associated Press) One of his pearls: "I have left orders to be awakened at any time in case of national emergency, even if I am in a cabinet meeting."

Reagan was tough. He not only survived an assassination attempt that missed his heart by an inch. He also had a bout of colon cancer. And he kept up a regime of rigorous exercise to stave off the fragilities of old age. One of them: a loss of hearing apparently caused by gunfire noise while he was filming all those Western movies in Hollywood.

Still, in his seventies he had begun to forget the names of his cabinet secretaries and other close aides.

But he delayed reporting the onset of Alzheimer's for five years after he left office. In a letter to the American people issued in 1994, he admitted that he had been told that he would be afflicted with Alzheimer's disease.

U.S. President Barack Obama, with former presidents Bill Clinton and George W. Bush, seen here in Washington, D.C., on January 16, 2010. (Mark Wilson/Getty Images) "I now begin the journey that will lead me into the sunset of my life," he wrote. That sunset would last another 10 years.

Reagan's successors have all been much younger. The oldest, George H.W. Bush, the father of President George W. Bush, was only in his sixties during his presidency. The younger Bush, Bill Clinton and Barack Obama were mere youngsters by comparison.

Now, though, it seems, we're back to the old days with both candidates being as old as Ronald Reagan. Neither appears to have the sense of humorous self-deprecation that carried the old trouper through it all.