Demographic characteristics of Sardinian centenarian genealogies: Preliminary results of the AKeA2 study

AbstractOBJECTIVEThis article provides an overview of the AKeA2 study, with a particular focus on data collection concerning family genealogies of the Sardinian centenarians and controls, and on the quality of these data. A first analysis of the main characteristics of the survey data is also summarized and selected preliminary results are presented.METHODSWe use descriptive statistics to analyze data collected by the AKeA2 survey on Sardinian centenarians and controls.RESULTSCentenarian women have on average fewer children, and at an older age, particularly for their last child. The mothers of centenarians, especially centenarian women, lived longer on average than those of deceased controls and controls born between 1905 and 1910 but still living at the moment of the survey.1. IntroductionIn Sardinia, male death rates after age 80 are only modestly higher than female death rates, and are lower than female levels in some municipalities. The remarkably low mortality after age 80 has thus yielded a surprisingly large number of centenarian men compared with centenarian women (Robine and Caselli 2005). An area with a large number of centenarians has been identified in the Sardinian province of Nuoro (Deiana et al. 1999; Poulain et al. 2004), as well as a longevity area for men. This latter area comprises municipalities in Oristano as well as Nuoro where the standardized death rate across old ages for men is less than 10% higher than for women, whereas elsewhere in the two provinces the standardized male death rate is more than 30% higher (Caselli and Lipsi 2006). The higher number of centenarians and their more balanced sex ratio have led to considerable interest among demographers, geneticists, gerontologists, and clinicians specializing in genetic mapping (DNA) (Caselli, Robine, and Rasulo 2003).The bio-medical characteristics of Sardinian centenarians was investigated by Luca Deiana and Giovannella Baggio (Deiana et al. 1999) in the AKeA study, an acronym derived from an expression in the Sardinian dialect that means "may you live to 100." A second, larger and cross-disciplinary study, called AKeA2, was launched in 2003, which involved demographers, historians, biologists, geneticists, and gerontologists. The demographic survey was directed by James Vaupel.This article gives a short description of the AKeA2 demographic survey and of the data collection, and provides a preliminary analysis of the data.2. Overview of the AKeA2 study: Sample selection and data collection planThe data collection was time-consuming. Over a six-year period various types of information were gathered: individual demographic characteristics, data on survival rates, and archival data regarding family characteristics and early-life events.The AKeA2 demographic survey was planned to involve Sardinian centenarians (100 men and 100 women) and their controls, by differentiating between living and deceased controls. All the controls were of the same sex as the centenarian, born and still resident in the same place of birth, and their day and month of birth were as close as possible to that of the centenarian. Picking the person with the most similar day and month of birth is a convenient method of selecting a matched individual, and this strategy controls for season-of-birth effects, which are known to affect longevity (Doblhammer 1999; Doblhammer and Vaupel 2001; Gavrilov and Gavrilova 1999).As concerns the living controls, the plan was to identify three younger controls for each centenarian by finding people born around 1907, 1912, and 1922. We also identified, for each centenarian, two deceased controls that were born, as mentioned before, the same year (and around the same day and month) and in the same municipality as the centenarian and to find one who died in his or her late 60s and one who died in his or her late 70s.In choosing both controls it was required that the family names of their mothers and fathers had to be different from the family names of the centenarian's parents. …