Dr. Charan Ranganath, a professor of psychology and neuroscience and director of the Dynamic Memory Lab at the University of California, Davis, writing in The New York Times:

Mr. Biden is the same age as Harrison Ford, Paul McCartney and Martin Scorsese. He’s also a bit younger than Jane Fonda (86) and a lot younger than Berkshire Hathaway CEO Warren Buffett (93). All these individuals are considered to be at the top of their professions, and yet I would not be surprised if they are more forgetful and absent-minded than when they were younger. In other words, an individual’s age does not say anything definitive about their cognitive status or where it will head in the near future.

I can’t speak to the cognitive status of any of the presidential candidates, but I can say that, rather than focusing on candidates’ ages per se, we should consider whether they have the capabilities to do the job.