To identify the area with the highest concentration of centenarians the so-called Extreme Longevity Index (ELI) was computed being the percentage of persons born in the place who became centenarians. The ELI for a given municipality was obtained by dividing the number of centenarians born in this municipality by the number of births that occurred in the same municipality from 1800 to 1900 included.
To test the hypothesis that the geographical distribution of centenarians in Sardinia is non-random and that a peculiar geographic area could be identified, where ELI is consistently and significantly higher than in the whole of Sardinia, we used a spatial deterministic model with the support of CI. Grasland from Université Paris Cité.
The results suggested the existence of a geographic area characterized by a higher prevalence of exceptional longevity. In this limited area grouping 15 villages, 91 persons, (47 men and 44 women) became centenarians of the 18,000 new born between 1880 and 1900. This is three-fold the number of centenarians expected based on the Sardinian average. The first Blue Zone was born.
Longevity Blue Zones 