What is a Blue Zone?
How a new blue zone is identified
Many centenarians in one place is not enough. Here is the demographic method behind every validated Blue Zone.
A Blue Zone is a geographically defined area where the people born there reach exceptional ages far more often than people born elsewhere.
That definition matters. Meeting several very old people in one village is a starting point for investigation, never a conclusion. Before an area can be recognised as a Blue Zone, its longevity must be demonstrated through rigorous demographic validation — in three steps.
Step 1
Individual longevity: validating every age
The first requirement is to establish that the reported longevity is real.
Each centenarian’s age is verified against reliable administrative documents, ideally original civil registration records. For centenarians who have died, the birth record and the death record must be linked beyond doubt to the same person. For those still living, the date and place of birth are confirmed by a birth record and, where available, by marriage certificates, population registers, identity documents, censuses or family records.
Genealogical reconstruction and conversations with the centenarian or their relatives can add valuable information. On their own, however, interviews are never sufficient: a memory is not a proof of age.
This first step exists to rule out age exaggeration, mistaken identity, duplicate records and other errors — before any conclusion is drawn about the longevity of the population.
Step 2
Population longevity: measuring the advantage
Once the ages are validated, a second question follows: do people born in the candidate area have a significantly greater probability of reaching 100 than people born elsewhere?
The preferred indicator is the Extreme Longevity Index (ELI).
The ELI compares the number of validated centenarians born in the area with the number of births recorded in the corresponding birth cohorts. It therefore estimates the probability that a person born in a given place will eventually become a centenarian, expressed per 100,000 newborns.
This birth-based approach is essential. Simply counting the centenarians among today’s residents can be misleading, because that figure is strongly influenced by migration and by the age structure of the population. An area may host many centenarians only because older people moved in, or because younger people moved away.
Step 3
Qualifying the area
he ELI is then calculated for a set of geographical units — municipalities, for example — to establish whether high longevity is concentrated in a geographically coherent area.
The ELI of that candidate area is compared with an appropriate reference population and with the national level. Taking the original Sardinian Blue Zone as the benchmark, two criteria have been proposed:
The two validation criteria
- The ELI of the candidate area reaches a level comparable to, or higher than, the one observed in the first validated Sardinian Blue Zone.
- The ELI is at least 50% higher than the corresponding national value.
An area qualifies as a validated Blue Zone only when all three conditions are met: the ages of its centenarians have been reliably validated, an exceptional longevity advantage has been demonstrated at population level, and the geographical concentration of that advantage has been established.
Five Blue Zones are validated today: a mountainous area of Sardinia, Okinawa in Japan, a group of municipalities on the Nicoya Peninsula in Costa Rica, Ikaria in Greece, and the French overseas department of Martinique.
Longevity hotspot, or Blue Zone?
This is the distinction the method makes possible.
A longevity hotspot is a place where many older people, including centenarians, currently live.
A Blue Zone is a population in which those born there show an exceptional capacity to survive to very advanced ages and reach 100.
Every validated Blue Zone is a longevity hotspot. But many longevity hotspots do not meet the criteria to be identified as a Blue Zone.
7 principles
The 7 Living Blue Zone principles are drawn from over 25 years of scientific observation in the regions of the world where people live the longest in good health. Not rules to follow — an invitation to create environments where living well becomes natural.