In 1999, a Belgian demographer, Michel Poulain, heard about an Italian island where people lived to be 100 and older while remaining mentally and physically active. Intrigued, Poulain visited Sardinia, where he validated people’s ages according to their birth records. Using a blue pen as he crossed the island, he marked on a map the spots where he found the oldest villagers. “From that time, it is called the blue zone,” he explained to me over the phone in June. In subsequent articles , books ,