AFTER JOE BIDEN was sworn in as the oldest president in American history in 2021, at age 78, questions swirled about whether there should be an upper age limit for the executive office. Now that we’re doing a different kind of math—Biden would be 86 at the end of a second term, and his presumptive rival, Donald Trump, would be 82—the question has become starker: Can someone in their 80s really have the mental dexterity and cognitive fortitude that the office requires?
Physiologically, we can’t stop our brains from changing. They start shrinking about 3 percent per decade after age 40, and that accelerates to about 5 percent per decade in our 80s. Our information-processing speed slows down, and it’s harder to quickly retrieve info or tune out background noise. Those functions likely get gummed up due to the hardening of blood vessels and the buildup of plaque in the brain.
Yet scientists are challenging
