Joe Biden was 78 when he took the oath of office as the 46th president of the United States in January 2021. This earned him the spot as the oldest president in U.S. history. Taking office at a time when the COVID-19 pandemic was taking an especially deadly toll on America's elderly population, Biden acknowledged his age. As he told hosts on "The View" during his candidacy, “It’s a legitimate question to ask about my age. Hopefully, I can demonstrate not only with age has come wisdom and experience that can make things a lot better.”

Born February 6, 1911, the nation’s 40th president was 77 years and 349 days old at the completion of his second term in January 1989. While campaigning in 1980, Reagan tried to put to rest questions about his age by pledging that he would resign if the White House physician ever detected signs of mental deterioration.

Once in office, Reagan proved to be remarkably resilient, and survived an assassination attempt in 1981, as well as surgery in 1985 to remove a cancerous polyp in his large intestine. Reagan always seemed the picture of robust health, in part because he exercised regularly with weights and enjoyed horseback riding and performing manual labor at his ranch in California. Reagan was able to brush aside concerns about age with humor, once joking during a 1984 debate that “I am not going to exploit, for political purposes, my opponent’s youth and inexperience.”

Born June 14, 1946, Trump was 70 when he won an upset victory in the Electoral College over Hillary Clinton. By January 2021, the 45th President was 74 years and 200 days old. Trump reportedly avoided exercise other than golf because he considered it unhealthy. He said in a July 2020 interview that a test showed he could recall a sequence of five words on a test designed to spot cognitive decline.

Born Oct. 14, 1890, the 34th President was 70 years and 98 days old when he left the White House in January 1961. The World War II hero was a regular exerciser who only weighed seven pounds more than when he graduated from West Point, according to biographer Jean Edward Smith. Nevertheless, he nearly didn’t make it out of his first term.

In 1955, while on a vacation in Denver, Eisenhower awakened with chest pains. Initially, his doctor didn’t realize the seriousness of his condition, and hours passed before a cardiac specialist was summoned from a nearby military hospital to give him an electrocardiogram, which revealed that the then-64-year-old president had suffered a massive heart attack. Eisenhower had to spend six weeks recovering in the hospital, but despite his ill health, his popularity was so great that he easily won reelection the following fall.

Born March 15, 1767, the 7th president was 69 years and 354 days when he completed his second term in March 1837. Though “Old Hickory” had a reputation for being a rugged ex-soldier and outdoorsman, by the time he reached the White House, he already had spent years coping with a variety of ailments.

According to biographer H.W. Brands, samples of his hair reveal that he had lead poisoning from old bullet wounds. Jackson also struggled with chronic diarrhea from diseases he’d contracted while fighting the Indians in the 1810s. His habits of smoking and chewing tobacco didn’t help his health either, and according to biographer Sean Wilentz, Jackson became so sick at times during his two terms that it appeared he might not survive.

Jackson did make it to the end of his term but when returned to the Hermitage, his plantation in Tennessee, the white-haired ex-president was physically spent and suffered from blinding headaches, insomnia, severe pains in his side and a chronic cough.

Born April 23, 1791, the 15th president was 69 years and 315 days old when his single term in office ended in March 1861. Buchanan was 50 pounds overweight and his hair already had turned white by the time he took office in 1857, but his health deteriorated even more rapidly under the strain of the job, according to biographer Jean H. Baker.

Buchanan had trouble remembering orders he had given, and he became so physically and mentally drained that he was unable to get out of bed some days, and made his advisors come to his upstairs library at the White House to meet with him. He also suffered from hand tremors.

Given the health difficulties that he struggled with, it’s probably not surprising that he failed in his single term to heal the rift between the slave and free states that led to the Civil War.

Born May 8, 1884, the 33rd president was 68 years and 257 days old when he left office in January 1953. Truman, who ascended to the presidency when Franklin D. Roosevelt died in 1945, was a diligent exerciser, who even in his sixties walked 1.5 miles each day at the same vigorous 120 steps-per-minute pace that he’d used while marching in the U.S. Army.

“He was in good shape,” William Seale, a historian and journal editor with the White House Historical Association, told CNN in 2016. But the strain of leading the nation through the brutal Korean War, and Truman’s habit of working 18-hour days and ignoring illnesses, almost got to him. In the summer of 1952, he became so sick that he had to be hospitalized, and doctors discovered that he was suffering simultaneously from three different bacterial infections. As an article from the National Archives website notes, the seriousness of his illness was kept from the public.

Born June 12, 1924, the 41st president had reached 68 years and 222 days in age when he left office in January 1993. After a long career in government that included a stint as Central Intelligence Agency director and eight years as vice president, Bush had a lot of mileage on his tires the time he reached the Oval Office. But a lifetime of exercise had kept the former Yale University baseball star remarkably fit for a man in his sixties.

Bush was a regular runner who frequently invited reporters along on his runs, former White House correspondent Kevin Merida later recalled in a piece for sports website The Undefeated. Bush did have some stumbles that some interpreted as signs of being tired and out of touch, including a moment in which he checked his watch during a 1992 debate and then had difficulty answering an audience member’s question about how the recession had affected him.

Though he lost the election, historians have come to appreciate his achievements as president, including his handling of the end of the Cold War.

It’s a common belief that the stress of being president tends to accelerate a person’s aging. But a 2011 study by S. Jay Olshansky, a professor in the School of Public Health at the University of Illinois at Chicago, found that U.S. presidents—at least the ones who weren’t killed by assassins—actually have tended to live longer than other American males who were their contemporaries.