Ogliastra and the Nuoro highlands, Sardinia

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A mountainous, historically isolated and comparatively poor area of eastern Sardinia, and the first region to be labelled a blue zone. Poulain, Pes and colleagues reported in the AKEA study of 2004 an unusually high density of male centenarians, and an unusual feature: a male-to-female centenarian ratio close to one, where the ratio elsewhere is typically one to four or five in women's favour. That anomaly is the strongest and the weakest part of the case — strongest because it is not what any ordinary demographic bias would produce, weakest because it is exactly the kind of extreme ratio that small-population noise or record error can generate. The population is genetically distinctive, with high frequencies of certain variants owing to long isolation, which has made it attractive for genetic studies of longevity; those studies have not identified a variant that accounts for the pattern.