Blue zones are regions in the world where people are claimed to live longer than average.[1] Examples of blue zones include Okinawa Prefecture, Japan; Nuoro Province, Sardinia, Italy; the Nicoya Peninsula, Costa Rica; and Icaria, Greece.[1] 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."[1]
The concept of blue zones having exceptional longevity has been challenged by the absence of scientific proof,[2] and by the substantial decline of life expectancy during the 21st century in an original proposed blue zone, Okinawa.[3]
History
The concept of blue zones resulted from demographic work published by Michel Poulain and colleagues in 2004.[4] They identified Sardinia's Nuoro province as the region with the highest concentration of male centenarians, referring to the area as the "blue zone" (a term chosen because the authors used a blue pen to mark a map of the villages with many centenarians).[1][4]
Initial analysis was that the apparent longevity of blue zone populations resulted from practice of a traditional lifestyle, including regular physical activity beyond age 80, providing family and community support for elders, and consuming locally produced food.[1]
Zones
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A 2013 study proposed four areas as blue zones:[1]
- Nuoro Province, Sardinia, Italy
- Okinawa Prefecture, Japan
- Nicoya Peninsula, Costa Rica
- Icaria, Greece
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.[1] The ELI was defined as the number of centenarians per 10,000 newborns, and was equated to the probability for any person born in that municipality to reach 100 years old and remain functional.[1]
During the period of births between 1880 and 1900 in the Sardinia blue zone, 47 men and 44 women eventually reached age 100, giving an average ELI value per 100,000 births of 508 for the blue zone location, whereas the rest of Sardinia had ELI values 2–4 times lower (less longevity).[1]
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.[1] 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.[1]
Several possible errors or limitations exist for these estimates, such as unreliability or absence of birth records.[1]
Life expectancy in blue zones is proposed to be as much as a decade or longer, compared to the average world life expectancy of 73 years in 2019.[5][6][medical citation needed]
Marketing
Loma Linda, California, United States, was included as a blue zone by Dan Buettner, founder of the marketing company, Blue Zones LLC, and popular press, which described the Seventh-Day Adventist community there as having unusual longevity due putatively to a healthy lifestyle and plant-based diet.[5][6] In 2020, Blue Zones LLC was acquired by the Seventh-Day Adventist health care system, Adventist Health.[7]
Scientific reception
A study of claimed longevity in Okinawa was unable to verify whether residents were as old as they claimed because many records did not survive World War II.[8] 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."[3]
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 solid science.[2]
See also
References
Further reading
- Eliza Barclay (11 April 2015). "Eating To Break 100: Longevity Diet Tips From The Blue Zones". NPR: The Salt. Retrieved 28 Jan 2022.