What science tells us about Biden, Trump and evaluating an aging brain

The 2024 presidential election has turned into a crash course in gerontology.

On Election Day, former president Donald Trump will be 78 years old, and President Biden will be a couple weeks shy of 82. Never have two people of such advanced age been the nominees of the major political parties, nor has there been a campaign so rife with suspicions and allegations that candidates are showing signs of age-related cognitive decline.

The situation has worried the electorate. In a Marquette Law School poll conducted in March, 77 percent of registered voters said they consider Biden “too old to be president,” while 52 percent said that of Trump. And in a Pew Research survey in April, 62 percent said Biden did not have the “mental fitness needed to do the job,” while 48 percent reached that conclusion about Trump.

But this public discussion of the aging brain ― a scientific topic if ever there was one ― has been conducted largely without reference to any scientific facts.

Research on aging, cognition and dementia has become more robust in a time when about 56 million Americans are over age 65, according to the 2020 Census. But medical and scientific experts warn that media reports and punditry about the candidates’ mental fitness have been marred by misinformation about the aging process.

The experts interviewed for this story were reluctant to speculate on the record about the cognitive health of Biden and Trump, noting that a robust assessment requires an in-depth examination potentially lasting days. They were more eager to speak about the aging process generally and what science can reveal about the aging brain - what’s normal, what’s pathological and how to discern the difference.

They also rejected any suggestion that there should be an upper age limit for the presidency.


Aging is not an unmitigated process of cognitive decline and deterioration, they pointed out. Judgment and emotional stability can improve with age - and may be more essential to effective leadership than, say, the ability to remember names or deliver a speech without a flub.

“The really important thing to keep in mind is that the older brain’s a wiser brain,” said Earl Miller, a professor of neuroscience at MIT. “Knowledge and experience count for a lot, and that can more than make up for slight losses of memory as a result of aging.”

Gaffes, fumbles and ‘word salad’

The president is the head of state, the commander in chief, the sole person with the power to order a nuclear strike. It is a demanding job that requires multiple skills, both in public and behind the scenes, and it requires stamina and clear communication. No job in America is so closely scrutinized.

Inevitably, verbal stumbles or any other whiff of mental decline are magnified by an often unmerciful news media.

When President Ronald Reagan ran for reelection in 1984 at the age of 73, his poor performance in a debate against Democratic challenger Walter Mondale, including halting speech in an obvious struggle to find the right words, incited allegations that he was showing signs of dementia.

Reagan rebounded in the next debate with a killer joke: “I am not going to exploit, for political purposes, my opponent’s youth and inexperience.” That brought down the house, and Reagan went on to win in a landslide.

In November 1994, nearly six years after leaving office, Reagan revealed in a letter to the American people that he had been diagnosed with Alzheimer’s disease. That incited a new round of speculation that Reagan had been cognitively impaired while still in the White House, but his defenders have argued the contrary.

In this election cycle, verbal fumbles have been a recurring storyline, with Biden and Trump often mangling names, places, dates and historical events, or routinely uttering “word salad,” challenging the listener to decipher what they are trying to say.

Biden, who has a lifelong stutter, has struggled with articulation at times, and Trump has mocked him for it. Many left-leaning pundits have pointed to Trump’s rambling, disorderly speeches as cognitive warning signs.

The most highly publicized stumbles by the candidates involve mixing up proper nouns. Biden said “Mitterrand” when he meant “Macron,” and Trump said “Haley” when he meant “Pelosi,” for example. Many older people struggle with proper nouns, in part because names are arbitrary labels.

Medical experts say these are just the workings of a normally aging brain, what are sometimes called “senior moments,” and not (absent further clinical investigation) signs of dementia or predictive of cognitive decline.

“They’re articulation problems, mainly, and this just happens as you get older,” said Charan Ranganath, a professor of psychology and neuroscience at the University of California at Davis.

Moreover, trouble retrieving words does not signal a deeper problem with memory.

“In my clinical work, you could see people who seemed young, vital, totally with it who had memory problems that wouldn’t allow them to function,” Ranganath said. “And I’ve seen people who are old, frail, they talk slowly, they move slowly and their memory is fine, and they’re perfectly capable of living on their own and working on their own.”

Experts note that, in contrast to children and young adults, there is tremendous variability in the mental and physical health of older people. There are 90-year-olds who are “superagers” and have the vitality and mental acuity of someone decades younger.

One way in which many older people have an edge on younger people is in emotional stability. As people age, they typically experience a decline in negative emotions, said Laura Carstensen, a professor of psychology and director of the Stanford Center on Longevity.

“Emotional regulation, emotional caring, appreciation, motivation to be social with others - all of those go up with age,” she said, adding her dismay at the tenor of the national discussion about aging political leaders. “The ageism that underlies these discussions is remarkable,” she said.


Trouble with distant diagnoses

Normal aging in the brain involves changes in the smallest components, as well as the broader systems. The machinery our cells use to convert glucose into energy and get rid of waste begins to break down. Cell debris builds up ― imagine a city during a garbage strike. As a result, neurons don’t function as they should. And a feature of aging called “stem cell exhaustion” results in the formation of fewer new neurons.

On average, the weight and volume of a human brain decrease by roughly 2 percent per decade due to a wide range of factors, including loss of cells as well as loss and shrinkage of connecting fibers called dendrites.

At the macro level, the gray matter that processes information and the white matter that helps different areas of the brain communicate with one another both decline in key areas called the hippocampus and frontal cortex. These declines weaken our working memory, attention and mental flexibility, leading to problems with word retrieval, among other things.

But these are gradual processes. Absent an injury or disease, cognition does not tend to decline precipitously, although the process does accelerate when people are close to death, said Allison Sekuler, a professor of psychology at the University of Toronto and at Baycrest Centre, a research and teaching hospital for older patients.

“If you map cognitive function and physical function onto chronological age, nothing lines up,” Sekuler said. “But if you plot it relative to time of death, then it lines up much better.”

What’s most important, Sekuler said, is looking at how a patient changes over time.

“Anyone who’s seeing changes in their emotion, in their speech, in their behavior, in their memory, in their sleep patterns, any of those things, if it’s concerning to you, definitely you should get it looked at,” Sekuler said, speaking of the population generally. “Whether it means that there’s cognitive decline, there’s so many other things that it could mean.”

Factors contributing to a memory or verbal slip could include depression, temporary dehydration or deficiency of the vitamin B12, she said.


“It’s very dangerous for us to be diagnosing people based on behavior, what we see in the media, what we see on the news,” she said.

A thorough neuropsychological evaluation is typically a holistic one, “which means it’s an inexact science,” said Ranganath, of UC Davis. It includes an interview and a set of memory tests. The patient might be asked to remember a list of words immediately after the examiner has said them, and then asked again 20 minutes later to recall as many as possible. A series of images, such as faces, can be used to test visual memory.

Memory deficits can be partial, he said: A person could have a deficit in visual memory, for example, but be fine with verbal memory. A doctor will find the results concerning only if the patient performs at an extremely low level, he said. Complicating the evaluation is the fact that cognitive functioning can vary over the course of a day, with many dementia patients becoming more agitated, anxious or confused in the late afternoon to evening.

A call for cognitive transparency

Voters may be tempted to make their own nonmedical assessments, since there is no requirement that candidates undergo a cognitive or psychological evaluation that can be shared with the general public.

The Biden administration in February released a six-page memorandum from his physician, Kevin C. O’Connor, summarizing a few medication-controlled physical ailments. The doctor concluded that Biden is a “healthy, active, robust 81-year-old male, who remains fit to successfully execute the duties of the Presidency,” the report said.

Biden did not, however, take a cognitive test. His doctor and a neurologist did not think Biden needed one, White House press secretary Karine Jean-Pierre told reporters. Just by doing his “very rigorous” job, she said, “he passes a cognitive test every day.”

Trump has claimed repeatedly that he has passed cognitive tests but has released minimal information about his health. In November, Trump released a three-paragraph note from his personal physician describing Trump’s health as excellent and saying “cognitive exams were exceptional,” but providing no details.

The medical journal the Lancet published an editorial in March saying the United States, if “truly invested in the health of its leaders, and not just grasping for fresh mud to sling,” should create a standardized system for sharing information about the health of presidents and candidates.

Biden and Trump, however, have been prominent public figures for decades and have both served as chief executive. Voters may feel they know them well enough to make a decision in November - and additional details about their health probably won’t sway supporters of either one.

Scott Clement contributed to this report.