# Blue zone

A blue zone is a region in the world where people are claimed to have exceptionally long lives beyond the age of 80 due to a lifestyle combining physical activity, low stress, rich social interactions, a local whole foods diet, and low disease incidence. The name blue zones derived simply during the original survey by scientists, who "used a blue pen on a map to mark the villages with long-lived population."
Suggested blue zones include Okinawa Prefecture in Japan, Nuoro Province in Sardinia, Italy, the Nicoya Peninsula in Costa Rica, and Icaria, Greece. The concept of blue zones has been challenged by the absence of scientific evidence. Subsequent research contradicted initial claims, such as Okinawa, which experienced substantial decline in life expectancy during the 21st century, and Nicoya, where people born after 1930 did not have exceptional longevity compared to the broader national population.

## History

A 1999 study of elderly people living on Sardinia found a prevalence of 13 centenarians per 100,000 population, indicating unusual longevity. A 2004 followup report showed that longevity was concentrated in the Nuoro province of Sardinia, specifically in its mountain regions where locally born men lived longer than those in the rest of Sardinia, although reasons for the longevity were unknown.
Beginning in 2005 in collaboration with American author Dan Buettner, the list of blue zone regions was extended from Sardinia to include Okinawa, Nicoya in Costa Rica, and Icaria in Greece. Belgian demographer Michel Poulain, who coauthored the 2004 report on Sardinia's longevity, added the French Caribbean island of Martinique as a new blue zone in 2019, while Buettner subsequently added Loma Linda, United States in 2008—which was first featured in his 2005 National Geographic article on blue zones—and Singapore in 2023. However, only the initial four blue zones – Sardinia, Okinawa, Nicoya, and Icaria – are recognized mutually by Poulain and Buettner.

### Estimating population longevity

In the original study of centenarians living in 14 mountain villages of Sardinia (the first proposed blue zone), the research team developed an Extreme Longevity Index (ELI) representing the ratio between the number of eventual centenarians born between 1880 and 1900, and the total number of births recorded during the same time interval for the region. 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.
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. The Sardinia and Okinawa blue zones had CR values for men substantially higher compared to several other countries, whereas values for women were mostly above those in other countries, while comparable to others.
Several possible errors or limitations exist for these estimates, such as failure to validate accuracy of ages, unreliable interviews or missing birth records.

### Business ventures

Dan Buettner trademarked the term "blue zone" in the United States in 2005. In 2008, he established the marketing company, Blue Zones LLC, with the intent to "[create] healthy communities across the United States" by partnering with municipalities to implement programs and policies based on principles derived from blue zones; cities deemed to have successfully enacted such changes receive a "Blue Zone Community" certificate.
The company recognizes Loma Linda, California as a blue zone after it was featured in Buettner's 2008 book, The Blue Zones, which described the city's Seventh-Day Adventist community as having unusual longevity due putatively to a healthy lifestyle and plant-based diet. However, Buettner admitted to featuring Loma Linda to his 2005 National Geographic article on blue zones because his editor wanted a U.S. location and Buettner "never bothered to delist it". In 2020, Blue Zones, LLC was acquired by the Seventh-Day Adventist health care system, Adventist Health, with Buettner remaining a consultant.
In 2024, the blue zone concept was featured in business promotion.

## Critiques

The concept of blue zone communities having exceptional longevity has been challenged by the absence of evidence.
It has also been questioned by the substantial decline of life expectancy during the 21st century in Okinawa, with the analysis concluding that "male longevity is now ranked 26th among the 47 prefectures of Japan". 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.
Costa Rica's "blue zone" is questioned, apparently resulting from a cohort effect.
Harriet Hall, writing for Science-Based Medicine, stated that there are no controlled studies of elderly people in the blue zones, and that blue zone diets are based on speculation, not evidence through a rigorous scientific method.