What makes a SuperAger?

The title says what makes a superager. But the article does not say why someone has one of the two things that makes them a superager.

>“What we realized is there are two mechanisms that lead someone to become a SuperAger,” Weintraub said. “One is resistance: they don’t make the plaques and tangles. Two is resilience: they make them, but they don’t do anything to their brains.”