Blue zones are regions in the world where people are claimed to live, or to have recently lived, longer than average. The notion is not based on scientific evidence but demographic anecdotes.
Five blue zones suggested are: Okinawa Prefecture, Japan; Nuoro Province, Sardinia, Italy; the Nicoya Peninsula, Costa Rica; Icaria, Greece; and Loma Linda, California, United States.
History
The concept of blue zones resulted from demographic work done by Gianni Pes and Michel Poulain, published in 2004. They identified Sardinia's Nuoro Province as the region with the highest concentration of male centenarians, referring to the area as the "blue zone".
Building on this demographic work, Dan Buettner proposed four additional locations: Okinawa, Nicoya, Icaria, and Loma Linda.
Zones
The areas having been identified as blue zones: Nuoro Province, Sardinia, Italy Okinawa Prefecture, Japan (currently disputed) Nicoya Peninsula, Costa Rica Icaria, Greece Loma Linda, California, United States
Scientific reception
A study of claimed longevity in Okinawa was unable to verify whether or not residents were as old as they claimed because many records did not survive World War II. When analyzed in the 21st century, life expectancy in Okinawa was deemed to no longer be exceptional when compared to the rest of Japan, as "male longevity is now ranked 26th among the 47 prefectures of Japan."
Harriet Hall, writing for Science-Based Medicine, stated that there are no controlled studies of elderly people in the blue zones, and the blue zone diets are based on speculation, not solid science.