In this era full of baby boomers caring for frail parents, we’ve seen plenty of documentaries, plays and memoirs about dementia, infirmity, loss. But in the HBO documentary “If You’re Not in the Obit, Eat Breakfast,” Carl Reiner and friends take up another side of the phenomenon of longer life spans: the many people in their later years who are still sharp and vigorous and engaged. The film, which has its premiere on Monday night, doesn’t pussyfoot around when setting its bar; no “life after 65” theme here. Mr. Reiner is interested in people 90 and above. What are their secrets for staying so energetic for so long? What are the frustrations of living in a society that tends to marginalize this age bracket? Mr. Reiner, who acts as host in the film, with Danny Gold directing, is himself Exhibit A for his study: He recently turned 95. In this breezy, anecdotal film, he chats with others in their 90s and beyond, many of them friends from show business, like Mel Brooks (90), Dick Van Dyke (91) and Betty White (95).

Read more at mobile.nytimes.com