For a decade, with support from the National Geographic Society, I’ve been organizing a study of the places where people live longest. The project grew out of studies by my partners, Dr. Gianni Pes of the University of Sassari in Italy and Dr. Michel Poulain, a Belgian demographer. In 2000, they identified a region of Sardinia’s Nuoro province as the place with the highest concentration of male centenarians in the world. As they zeroed in on a cluster of villages high in Nuoro’s mountains, they drew a boundary in blue ink on a map and began referring to the area inside as the “blue zone.” Starting in 2002, we identified three other populations around the world where people live measurably longer lives than everyone else. The world’s longest-lived women are found on the island of Okinawa. On Costa Rica’s Nicoya Peninsula, we discovered a population of 100,000 mestizos with a lower-than-normal rate of middle-age mortality. And in Loma Linda, Calif., we identified a population of Seventh-day Adventists in which most of the adherents’ life expectancy exceeded the American average by about a decade. …

Ikaria, an island of 99 square miles and home to almost 10,000 Greek nationals, lies about 30 miles off the western coast of Turkey. Its jagged ridge of scrub-covered mountains rises steeply out of the Aegean Sea. Before the Christian era, the island was home to thick oak forests and productive vineyards. Its reputation as a health destination dates back 25 centuries, when Greeks traveled to the island to soak in the hot springs near Therma. In the 17th century, Joseph Georgirenes, the bishop of Ikaria, described its residents as proud people who slept on the ground. “The most commendable thing on this island,” he wrote, “is their air and water, both so healthful that people are very long-lived, it being an ordinary thing to see persons in it of 100 years of age.”

Seeking to learn more about the island’s reputation for long-lived residents, I called on Dr. Ilias Leriadis, one of Ikaria’s few physicians, in 2009. On an outdoor patio at his weekend house, he set a table with Kalamata olives, hummus, heavy Ikarian bread and wine. “People stay up late here,” Leriadis said. “We wake up late and always take naps. I don’t even open my office until 11 a.m. because no one comes before then.” He took a sip of his wine. “Have you noticed that no one wears a watch here? No clock is working correctly. When you invite someone to lunch, they might come at 10 a.m. or 6 p.m. We simply don’t care about the clock here.”