The writer is the author of “Extra Time: Ten Lessons for an Ageing World”

Is the rash of US presidential candidates aged over 70 a sign of weakness or strength? We hear that Bernie Sanders isn’t too left; he’s too old. Michael Bloomberg was alive when Harry Truman was in the White House. Joe Biden is surely as worn out as his shoe leather.

In reality, all of these characters seem in remarkably good shape. Despite being the oldest president ever to be sworn in (he was 69), Donald Trump still acts like a kid.