In an era of instant communication, the American public expects to know the facts about the health of its presidents. So it's no secret that Barack Obama has the heart rate of an athlete but struggles with vices such as cigarettes and pie, which contribute to his high cholesterol.

But such transparency was far from typical until recent decades. Previous commanders-in-chief hid their illnesses, afflictions and even their surgeries from the public.

"I think we forget that it's only in the last 50 years that people have come to accept illness as something we could discuss openly," said Dr. Jacob Appel, a bioethicist and medical historian who practices psychiatry at Mount Sinai Medical Center in New York City.

"It wasn't part of the public discourse," Appel said. "I'd prefer to live in a world where people can embrace that our [public figures] can be ill, and still be great leaders. Now that this information is open, I think it can be for the greater good."

Perhaps the most notable examples of secrecy occurred during the administrations of Grover Cleveland, Woodrow Wilson and Franklin D. Roosevelt, said Dr. Robert Lahita, chairman of the department of medicine at Newark Beth Israel Medical Center in New Jersey, and an avid researcher of presidential ailments.

Secret surgeries & strokes

For instance, Lahita said, amid the 1893 financial panic, Cleveland discovered a lesion on the left side of his palate that was said to be cancerous . As Americans waited for him to create economic stability, the president had the tumor clandestinely removed while sailing on the yacht Oneida to his summer home. The crew was sworn to secrecy.

"It would have been catastrophic for him to announce he had cancer," Lahita said. "The economy teetered on the brink of collapse. Now, if anything had gone wrong on that boat ... it would have been the end of the United States as we know it."

During the Wilson administration in 1918, the president suffered a stroke while on a speaking tour of the Western states that rendered the left side of his body immobile. His first lady, the secretary of state, his personal physician and private secretary all kept his condition secret.

"It is now accepted that the first lady, in actuality his second wife, really acted as president for most of Wilson's term," Lahita said.

And then there was Franklin Roosevelt.

FDR's polio which required the use of a wheelchair, crutches and leg braces was largely kept from the public. According to the University of Arizona, Roosevelt won the cooperation of news reporters to minimize the extent of his condition, and was generally photographed only above the waist.

Nor were Americans told he was diagnosed with the deadly skin cancer melanoma during his second term. The malignancy, which started with a brown lesion over Roosevelt's left eyebrow, eventually killed him after spreading to his abdomen and brain, Lahita said.

It was, however, widely known that FDR had serious heart problems at the end of his life. FDR's official cause of death was a massive stroke, which he suffered in April 1945.

Mental illness and the rise of transparency

Mental illness has affected about half of all U.S. presidents, Lahita said. Abraham Lincoln suffered from severe depression , John Adams suffered from bipolar disorder and James Madison was stricken with a high fever during for three weeks that left him "deranged," Lahita said.

"At that time, presidents could disappear for six months at a time," which helped Madison hide his condition, Lahita said. "He probably had cerebral malaria, which can be fatal."

Beyond that, a host of possible conditions some figured out by modern health experts centuries after the presidents died afflicted many commanders-in-chief. George Washington is thought to have had Klinefelter syndrome, in which males carry an extra X chromosome and can be infertile, Lahita said. Washington had no children with his wife, Martha, but adopted her two kids from her first marriage.

Chester Arthur probably had chronic kidney disease , and John F. Kennedy likely had Addison's disease, an adrenal gland disorder that could have contributed to his jaundiced skin and bouts of weakness, Lahita said.

"Kennedy was really the last one to sequester his illness," Lahita said. It's possible JFK might not have won his election if the information had been out, but because the public knew little about Addison's disease, it's also possible JFK's condition would have had no effect.

The information tide turned in 1967, when the 25th constitutional amendment was passed to ensure presidential illnesses would be disclosed, and to delegate duties to the vice president in cases of disability.

Appel contended that political figures, in revealing their conditions, come out looking stronger.

"In judging our political leaders, we should view them as lenses to what these people have overcome," said Appel, who has advocated for DNA testing of long-gone presidents' possessions to reveal health conditions and possible descendants.

"I think it's a great example when presidents can serve as role models," he said. "Much of what the public learns [now] about the president is for political reasons, but that doesn't mean it can't have ancillary benefits for all of us."

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