Hillary Clinton's health has become a central issue in the US election, with her rival Donald Trump promising to reveal his own medical data this week in response to Mrs Clinton's travails over the weekend.
The revelation that Mrs Clinton is suffering from pneumonia, made after she was filmed stumbling at a 9/11 memorial ceremony, has raised questions about both the Democratic candidate’s medical condition and her campaign’s openness in discussing it.
Mr Trump, who wished Mrs Clinton well in his appearance on Fox News on Monday morning and pledged to reveal the details of a recent physical this week, could benefit from such a controversy as the US presidential campaign heats up.
But it is far from the first time that the health of a president or presidential candidate has turned into a central issue in the country's politics. Over the past century, many occupants of the White House have battled with health problems - and have often been less than frank about their ailments.
Woodrow Wilson: President, 1913-1921
In the midst of a campaign to promote the Treaty of Versailles across the US in 1919, Wilson suffered a severe stroke that left him incapacitated until the end of his presidency. Despite his bad health Wilson remained in office until the end of his term in 1921 - made possible by his second wife Edith, who acted as a mediator between the largely immobilised president and his cabinet.
Franklin D Roosevelt: President, 1933-1945
Roosevelt was diagnosed with polio in 1921 at the age of 39. Despite the disease leaving him unable to stand or walk without support, he went on to serve 12 consecutive years as US president. Throughout his time in office, Roosevelt avoided disclosing the full extent of his condition: Although he used a wheelchair in private, he avoided doing so in public.
Dwight Eisenhower: President, 1953-1961
Eisenhower lived through three major medical crises while in office. In September 1955 he suffered a heart attack that resulted in several weeks of hospitalisation. Less than a year later, he underwent urgent surgery to treat Crohn's disease, an inflammatory condition of the intestine, and in late 1957 he suffered a light stroke that left him temporarily unable to speak. But he recovered and his second term was comparably free of medical woes.
John F Kennedy: President, 1961-1963
Details of Kennedy's ill-health were largely unknown during his presidency, and have emerged only since his assassination in 1963. Questions have been raised about whether heavy medication might have had an impact on his political decisions. In 2002, historian Robert Dallek described a president constantly suffering from degenerative bone disease and heavily medicated to soothe severe back pains. According to Dallek, JFK was hospitalised nine times during his 2 ½-year presidency, a fact kept secret at the time.
Ronald Reagan: President, 1981-1989
Reagan, who at 69 was the oldest US president ever to assume office, underwent several surgeries that raised questions as to whether he was medically fit for office. In 1985 he transferred presidential authority to his vice-president, George HW Bush, for eight hours while he underwent a procedure to remove cancerous polyps from his colon.
George H W Bush: President, 1989-1993
In 1992, Mr Bush vomited and then fainted in front of television cameras at a banquet hosted by the prime minister of Japan, Kiichi Miyazawa. His spokesman later insisted Mr Bush was simply suffering from intestinal flu but was fine otherwise.
The Financial Times