In recent years, most candidates have released their personal health information in statements from their doctors or through interviews. The practice grew out of retrospective analyses of the health of presidents that document how some presidents hid or lied about their health problems, often aided by their doctors. Occasionally, White House doctors have misdiagnosed a president’s heart and vascular problems.

Experts believe that President Warren Harding died of a heart attack that his doctor did not detect. Toward the end of President Franklin D. Roosevelt’s third term and until his death in his fourth term, his White House doctor withheld the fact that he had serious heart failure. President Dwight D. Eisenhower suffered a heart attack near the end of his first term. Examination of his older medical records has provided strong clues that he had a heart attack before he ran for president.

In 1999, former Senator Bill Bradley of New Jersey damaged his presidential campaign by not disclosing that he had a number of episodes of atrial fibrillation (a heart rhythm abnormality) before he experienced one while campaigning and had to rush to a hospital in the Bay Area with reporters trailing him.

Among the current candidates , Joseph R. Biden Jr. underwent emergency surgery in 1988 for a near-fatal ruptured berry aneurysm of an artery in his brain. He also underwent surgery to remove a second berry aneurysm. New cerebral aneurysms can develop years later in a tiny percentage of individuals who have survived one. In 2008, Mr. Biden’s doctor said that he had recovered fully, and that he did not need further tests to detect a new berry aneurysm because he had done well for 20 years.

Modern medicine has enabled many individuals with heart disease and other chronic ailments to successfully run for office and fulfill their duties. Nevertheless, Mr. Sanders’s stent episode is likely to renew a measure of voter interest in the health of its 2020 presidential candidates. Two other leading Democratic hopefuls are in their 70s and President Trump is 73. All of them, as well as Mr. Sanders, may well be medically fit to serve, but Americans have never faced the prospects or consequences of so many top candidates who were past the official retirement age.