From the article: "clerical errors, natural disasters, and pension fraud were better explanations for the proportion of centenarians “discovered” in these discrete regions of the world."

That was discovered in Japan around 2010.[1] The Tokyo municipality sent out people to visit everyone over 100 to find out what they were doing right. What they found was that about 80% of them were unaccounted for, but collecting benefits.[1][2]

[1] https://www.bbc.com/news/world-asia-pacific-11258071

[2] https://www.npr.org/2010/09/20/129992827/tracking-down-japan...