[1] Examples of blue zones include Okinawa Prefecture, Japan; Nuoro Province, Sardinia, Italy; the Nicoya Peninsula, Costa Rica; and Icaria, Greece.
[2] Beginning in 2005 in collaboration with author Dan Buettner, the list of blue zone regions was extended from Sardinia to include Okinawa, Nicoya in Costa Rica, and Icaria in Greece.
[2] The ELI was defined as the number of centenarians per 10,000 newborns, and was used to determine the probability that any person born in that municipality would reach 100 years old while remaining mentally and physically functional.
[2] Another longevity index applied was the Centenarian rate (CR) for the 1900 birth group (number of persons surviving to 100 years old per 10,000 people alive at age 60) in December 2000.
[4] Michel Poulain, one of the authors of the original paper about blue zones, conducted a study in 2011 to validate the claims of longevity in Okinawa, and was unable to verify whether residents were as old as they reported due to many records not surviving World War II.