Segment 1: A new book on aging proposes a third stage in life. First comes childhood, then adulthood and finally, elderhood, which begins roughly in your 70s and can last for decades. It comes with a unique set of challenges, joys and needs, and our cultural reluctance to acknowledge that comes at a cost. Louise Aronson , geriatrician and professor of medicine, University of California San Francisco; author, Elderhood: Redefining Aging, Transforming Medicine, Reimagining Life Segment 2: How 816