User blog comment:Xilinoc/Ch. 850 - Oda's Still Got It/@comment-24442815-20161222224928/@comment-5398287-20161222230624

I'd imagine disease and debilitating bodily conditions contribute to a lower lifespan. Even people in the real world have different lifespans just based on their ethnicity, location, and gender. Kureha's basically Queen Elizabeth II but more shapely.