For people in their mid-70s such as myself, the 2020 presidential campaign is an oddly personal experience. Among the front-runners for the Democratic and Republican nominations are two men our age (Joe Biden, 76, and Bernie Sanders, 77) and another just a few years behind us: Donald Trump, 72, the oldest man ever elected president. If Trump had lost in 2016, Hillary Clinton, at 69, would have been the second-oldest person ever elected.

Is this okay? Can politicians our age be effective presidents? It’s a question that can provoke strong, often pained reactions from my contemporaries. Any one person’s answer reflects their sense of what it takes to be president and what it means to be in your 70s. In my own case — healthy, active, marbles still present but unmistakably 76 — this does not seem like a good stage of life to take on such a huge challenge. I have less energy and less stamina than I did 25 years ago. I find concentration more difficult and naps more necessary. Learning a new subject is much harder than it used to be.

For my generation, the archetypal presidential geezer was Ronald Reagan, the only man (until Trump) ever to celebrate his 71st birthday in the White House. But Reagan was a spry 69 when he won the job. If Biden or Sanders triumphs in 2020, we enter an unprecedented age of — well, of old age in power. If reelected in 2024, Biden would start his second term at 82, Sanders at 83. If Trump won again, he’d still be president at 78 — 15 years older than Franklin D. Roosevelt was when he died in office in 1945.

Several dozen contemporaries with whom I’ve discussed this article, and half a dozen gerontologists, agree that 50 is a better age than 76 to undertake perhaps the hardest job on Earth. The experts on aging (none as old as I) were generally more sympathetic to the idea that someone in their late 70s might be an effective president, but no one I’ve talked to thinks this is an ideal age for the role. The specialists know the numerous studies that show, unmistakably, that on nearly every scale of intellectual capacity, people over 70 have less to offer than younger generations. The one exception is the ability to learn and recall vocabulary.

Studies of old people conclude that between 16 percent and 23 percent of Americans over 65 experience some form of cognitive impairment. Researchers from the Georgia Institute of Technology found that these subjects performed worse than others on tasks involving working memory — the ability to remember information while manipulating it, as when calculating the tip on a restaurant bill — and that they’re more impaired when those tasks become more complex. Older adults also have difficulties with tasks that require dividing or switching attention, like cooking while chatting on the phone. On tests of reasoning, memory and cognitive speed, the average scores for adults in their early 70s were near the 20th percentile of the population, whereas the average performance for adults in their early 20s was near the 75th percentile. A Mayo Clinic study of 161 cognitively normal adults between 62 and 100 years of age showed that declines in learning ability closely track the passage of time. “Research has shown that concept formation, abstraction, and mental flexibility decline with age, especially after age 70, as older adults tend to think more concretely than younger adults,” according to researchers at the University of Alabama at Birmingham, who surveyed several studies. I would hope that impaired executive functioning is not the sort of torture Americans want their president to suffer.

People in my generation have entered the time of dying. Life expectancy for men in the United States is less than 79 years. According to the actuarial tables used by life insurance companies, those of us lucky enough to remain standing at 75 still have, on average, about a decade to go, but of course averages don’t apply to any individual. I recently checked on my college class from 1964. We were 1,000 men at the time, and we’re about 785 today — more than 20 percent of my classmates are already dead. Per the insurers’ tables, a President-elect Biden in 2020 would have a 26 percent chance of dying within the next five years; Sanders in 2020 would face a 29 percent chance of dying within five years; for Trump, it would be about a 20 percent chance of death before 2025.

Sen. Bernie Sanders (I-Vt.), 77, speaks during a rally in Fairfield, Iowa, on April 6. He and Joe Biden are among the early front-runners in the Democratic presidential primary race. (Scott Olson/Getty Images) Former vice president Joe Biden, 76, attends a union conference in Washington on April 5. Like Sanders, if he was elected in 2020, he would be in his 80s by the end of his first term. (Tasos Katopodis/Getty Images) President Trump, now 72, is the oldest man ever to be elected U.S. president. (Bill OLeary/The Washington Post)

TOP LEFT: Sen. Bernie Sanders (I-Vt.), 77, speaks during a rally in Fairfield, Iowa, on April 6. He and Joe Biden are among the early front-runners in the Democratic presidential primary race. (Scott Olson/Getty Images) TOP RIGHT: Former vice president Joe Biden, 76, attends a union conference in Washington on April 5. Like Sanders, if he was elected in 2020, he would be in his 80s by the end of his first term. (Tasos Katopodis/Getty Images) ABOVE: President Trump, now 72, is the oldest man ever to be elected U.S. president. (Bill OLeary/The Washington Post)

This is a sensitive topic. We live in an age of isms, and ageism (discriminating against people because of how many birthdays they’ve celebrated) is forbidden by statutes like the Age Discrimination in Employment Act, and by political correctness. But the unwillingness to discuss this decline bothers some people in the field of gerontology. “If talking about someone’s age is taboo and we are immediately accused of ageism, then that shuts down the discourse,” argues Jennifer Sasser, 52, a gerontologist at Oregon State University. A 70-year-old candidate “will have 20 more years of lived experience than a 50-year-old, and that translates not only into potential expertise but also a richer mind,” Sasser says. But “you can’t stay at the height of your capacity forever. That’s not the trajectory. We do become less energetic. Our bodies and minds do change.”

Sasser’s co-author of the widely used text “Aging: Concepts and Controversies,” Harry R. Moody, 74 — a gerontologist who was once director of academic affairs at AARP, the lobby for older Americans — also laments the silence about how age can affect politics and politicians. “You find lots of discussions about gender, ethnicity, class, race, trying to explain what’s going on with white nationalism, et cetera,” he says. “But you never find any discussion of age. This is peculiar.”

One reason is the wide range of capabilities of old people. Some 80-year-olds seem and act younger than some 60-year-olds. “Age per se should not disqualify a candidate,” says Denise C. Park, 67, a psychologist who founded the Center for Vital Longevity at the University of Texas at Dallas. “Older brains are packed with knowledge and experiences that may constitute ‘wisdom’ and would help a president perform well in office,” she said, but she added that age obviously brings certain costs, “specifically in their capacity for quick processing of new information, remembering details, and the ability to process and use new information.”

Park endorsed the idea that older candidates should volunteer for a neurological assessment, which can reveal precursors to degenerative disorders such as Alzheimer’s, and disclose the results. “All brains show some degradation over time, but the fact that older people have degraded brains does not necessarily mean [they have] less useful mental skills,” she observed. “The additional knowledge and experience that comes with age may compensate for this.”

Two of my contemporaries rejected my view that we are too old to be effective in the White House. One was Bill Bradley, 75, an NBA Hall of Famer and former U.S. senator from New Jersey who ran for president in 2000, when he was 56. “You could do it at 76, absolutely. Depends on health, physical conditioning, how active your mind has been, your own self-awareness,” says Bradley, now an active investment banker in New York. “You’d bring a lot of wisdom. It’s a little like being a basketball player . . . Over time, you learn how to play smart, so you don’t have to make as much effort in your 10th year as you did in your first to get the same result.” (It’s worth noting that in Bradley’s 10th year in the NBA, he was 33.)

A second dissent came from Harold Varmus, 79, who has one of the most remarkable résumés of my generation. Varmus won the Nobel Prize for physiology at age 49, then over a 22-year period ran three famous scientific institutions: the National Institutes of Health, Memorial Sloan Kettering Cancer Center in New York and the National Cancer Institute. Varmus told me he wasn’t sure that “anyone is competent to be president of the United States,” but yes, he thought he could do it. “I’m still pretty good at learning new stuff,” he said, and I believed him. He said his judgment, writing ability, perspective and demeanor had all improved in his late 70s.

Yet Varmus highlights the exact problem: Any given human could function at a high level well into his or her dotage. But these are outliers. The overwhelming majority decline. This happens to different people at different ages, but scientists have established that decline accelerates with advancing age: In a study at the University of Virginia, adults between the ages of 61 and 96 showed a decrease in cognitive speed twice as great as adults under age 60, and a drop-off in memory four times as great. Memory loss causes “slowed processing speed, reduced ability to ignore irrelevant information, and decreased use of strategies to improve learning and memory,” according to the University of Alabama’s meta-study.

Mary Roman, a prominent cardiologist at Weill Cornell medical school, recalled President George W. Bush’s early years in office, which he assumed when he was 54. At first, Bush compared the presidency to a CEO’s role, and he tried to make it a “nine to five enterprise.” But the 9/11 attacks, the rise of the Internet and the 24-hour news cycle changed the job. “The president had to be working, responding, all the time,” she says. “Look at the photographs of Bush and Obama, and how the presidency changed them.” Roman is 67, and she “couldn’t imagine taking on a 24/7 job” at her age.

Someone in his or her mid-70s undoubtedly could perform the job of president, but how effectively? The example of our 72-year-old incumbent raises questions about the meaning of “perform.” Is there any reason to think that picking someone with at least a 20 percent chance of dying in office is a good idea? Don’t we have a great many younger candidates who are more likely to survive and thrive in this most arduous of jobs?