Exceptional Longevity in Okinawa:

Abstract

Abstract The topic of this article is the exceptional longevity in Okinawa. This phenomenon should be thoroughly validated at both the individual and population levels. This contribution analyzes the demographic data available for the population of Okinawa, in order to explain the presence of large numbers of centenarians. The mortality crossover obtained by comparing mortality rates in Okinawa and Japan could be attributed either to different behavior of the generations born before and after WW II, or to bad data. Arguments are presented in favor of both possible explanations. The reconstruction of the Koseki to replace the original, which was destroyed during WW II, could be a source of misreporting of age and would support the bad data hypothesis. Nevertheless, no concrete proof of invalid data has been found. Therefore, the author does not favor either of these explanations, but is calling for a more in-depth validation of longevity in Okinawa. (ProQuest: ... denotes formula omitted.) 1. Introduction Okinawa is one of the 47 prefectures of Japan. It consists of a group of 44 inhabited islands that extend 800 miles south of the main Japanese islands, north of Taiwan. These islands, part of the Ryukyu Kingdom, were incorporated into the Japanese Empire in 1879. The people of Okinawa still consider themselves different from those of mainland Japan, and there are dissimilarities between some features of their cultures and traditional life styles. For 80 days in 1945 Okinawa was the site of the last and most decisive battle of WW II between Japanese and American soldiers. More than 100,000 soldiers died, as well as an equal number of civilians. The territory was subsequently under U.S. administration until 1972, when it was returned to Japan. Its population of 1.3 million inhabitants is considered to be among the less economically developed of Japan. Since the excellent contribution of Irene Taeuber (1955), no in-depth studies of the demography of Okinawa have been conducted, although these are essential in order to validate its alleged exceptional longevity. Studies of centenarians are frequently used to investigate the determinants of healthy aging and exceptional longevity. Most of these studies involve individual centenarians and compare their behaviors and characteristics with younger members of the same population.2 A few other studies have analyzed populations which are somewhat isolated and often ethnically distinct that experience exceptional longevity. These studies assess not only individual longevity but also the longevity of the population as a whole. The mountainous areas of Sardinia and Okinawa are the two most important regions where population longevity has been recently investigated in more detail.3 Verification of extreme age and exceptional longevity is crucial to the validity of all research on the oldest olds. Individual longevity and population longevity are complementary concepts that may contribute to the analysis of the determinants of longevity, but their validation process differs. For individual longevity, the age of every oldest old person is carefully checked before inclusion in the analysis, or exclusion in case of error. For population longevity, individual age validation is also required,4 but an exhaustive enumeration of the oldest olds has to be ensured from a basic analysis of the demographic evolution of the population. A recent paper by Willcox et al. (2008) might be considered to be a direct response to the need for a complete validation of population longevity in Okinawa. It presents a battery of arguments that support the conclusion that the high prevalence of centenarians in Okinawa is valid and warrants further study of its genetic and environmental correlates. The present article intends to revisit these arguments, to assess the demographic aspects of the longevity of the population of Okinawa, and also to consider recent research by Saito (2010) on the age validation of super-centenarians in Japan. …