The word "centenarian" means people who have lived one hundred years or more, in other words, people who have lived a "century." Centenarians are important to study because they are living examples of successful aging. Our work suggests that most centenarians have been remarkably healthy and experienced a rapid terminal decline late in life, resulting in a compression of morbidity to their final years (Bernstein et al., J Gerontol Biol Sci. 2004; Willcox DC et al. Am J Geriatr Psychiatr. 2007).
Okinawa's elders (aged > 70 years) and centenarians in particular, also seem to have experienced a slower age-related decline and markedly delayed or avoided entirely the chronic diseases of aging, such as Alzheimer's Disease, cardiovascular disease and cancer.
How Many Centenarians are There?
According to recent estimates there are approximately 80,000 centenarians in the United States, or about 10-20 centenarians per 100,000 population, although this is difficult to estimate precisely since there was no national birth registration system in the U.S. until 1940. However, the U.S. Census Bureau estimates these numbers will top one million by the year 2050. Although regional differences exist these rates are similar to other developed nations. In Okinawa, centenarian ratios may be the world's highest at approximately 50 per 100,000 population representing 740 centenarians in a population of 1.3 million of which 90% are women (Japan Ministry of Health, Labour and Welfare, 2006).
Do Super-Centenarians Exist in Okinawa or Elsewhere?
Reports that came from the former Soviet state of Georgia and surrounding states in the Caucasus Mountains, Hunza Valley in Pakistan or Vilcabamba in Ecuador claimed unprecedented concentrations of centenarians, with many living beyond the age of 120 years. In-depth studies of these populations have shown that age-exaggeration is rampant and life expectancy is actually shorter than in the U.S., nor are there high concentrations of centenarians.
The reasons behind the age exaggeration are complex but include the prestige that goes along with being the oldest individual in a village, avoidance of military service while young by assuming the identity of a deceased elder, and a general tendency for the elderly to inflate their ages. Age inflation exists in most age databases that rely on census data for their centenarian statistics, including in the U.S., where a national birth registration system did not exist at the time centenarians were born (see Leaf A. J Am Ger Soc 1982;30:485-7). In Okinawa, a family registry (Koseki) dates back to 1879 so age verification is possible for all citizens, including centenarians.
However, there is another geographic area where there is an unusually long life expectancy and a high prevalence of centenarians-Sardinia, Italy.
Sardinia has higher prevalence of centenarian than elsewhere in Italy (Caselli et al., 2003) and many of them are concentrated in a small area, with a particularly high prevalence of male centenarians. The existence of a greater prevalence of centenarians in Sardinia largely depends on reduced mortality risk between 80 and 100 years, in particular, there appears to be reduced mortality for circulatory diseases (Deiana et al., 1999; Passarino et al., 2002; Caselli et al., 2003; Poulain et al., 2004).
Thus, lower mortality for the major causes of death-circulatory disease and cancer accounts for much of the high centenarian prevalence in Sardinia. This combined with relatively higher female mortality, appears to account for the relatively high prevalence of male centenarians in Nuoro province, which are half as prevalent as their female counterparts, as compared to about one fifth in most countries.
Why Did We Only Recently Hear About the Okinawan Longevity Phenomenon?
You'd have thought such a fascinating discovery would have been big news in the West, but it went largely unnoticed for a number of reasons. First, only a few small research reports made it into the English-language scientific literature. Most of the interesting findings (more than 100 peer-reviewed studies) were published in the Japanese scientific literature always in Japanese, making them fairly inaccessible to Western scientists. Second, gerontology and preventive medicine research were relatively new in the 1970s, and baby boomers were not old enough to get the diseases of premature aging. Research dollars were only just beginning to flow into this area of investigation. Finally, Okinawa's role as a battleground in World War Two and its continuing problems with U.S. and Japanese military bases tends to overshadow its role as an area of extreme longevity.
The Reason for the Dramatic Increase in the Number of Centenarians in Okinawa and Around the World:
Centenarians are the fastest growing demographic group in many developed nations including the USA and Japan. In 1963, when the Japan Ministry of Health and Welfare began tabulating the centenarian population, there were only 153 centenarians in the whole of Japan. By 2006 this number had grown to 28,395 and women made up 85% of the total. Likewise, in Okinawa the first centenarians did not appear until the mid-1960s yet their numbers have mushroomed to 740 and this figure will double within the next five years. This increase in the number of centenarians worldwide is mainly due to larger and healthier birth cohorts who have had access to better medical care, public health infrastructure, housing, income, and nutrition than previous cohorts.
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