Tuesday, May 13, 2008

Centenarian Prevalence in Okinawa

Okinawa in Japan has among the world's highest reported prevalence of centenarians. And for scientists interested in human longevity this makes the population in Okinawa very interesting and important.

Yet verifying centenarian prevalence is of course difficult for a variety of reasons. But this article in the latest issue of The Journals of Gerontology Series A: Biological Sciences and Medical Sciences makes the case for validating the centenarian prevalence in Okinawa. Here is a sample from the study:

THE National Institute on Aging (NIA) Advisory Panel on Exceptional Longevity (APEL) (1) and the NIA strategic plan (2) have identified healthy aging as a research priority. However, few individuals survive to exceptional ages in robust health. Centenarians possess genetic and/or environmental attributes that allow them to survive to exceptional ages, and many appear to delay or avoid major age-related diseases and disability (3,4). Okinawa, the southwesternmost prefecture of Japan, is an isolated island population that possesses the longest life expectancy and the lowest risk for major age-related, chronic diseases in Japan, the world's longest-lived country (5–7). Geriatric studies of the older population also demonstrate that Okinawans appear to have high physical and cognitive function at older ages (3,8,9). Consistent with these studies, the Japanese government's Annual Centenarian Report ranks Okinawa as having the highest prevalence of centenarians of any prefecture within Japan (10). Therefore, the Okinawan population may be important for further study of genetic and/or environmental traits that lead to exceptional longevity, including longevity with good health. However, studies of exceptionally aged persons require precise definitions of phenotypes, the most important of which is accurate age for the study participant.

.... As the world's population ages, increased research emphasis has been placed on identification of populations with high prevalence of healthy, older individuals for the study of healthy aging and exceptional longevity (1,2). Precise phenotyping, particularly accurate age, is required. This is especially important for genetic studies of human longevity; therefore, age validation has become an important part of such research (7,15,16,23,33,34). Thus, the purported high prevalence of centenarians in Okinawa has been a subject of keen interest and some controversy.

.... We hypothesize that the Okinawa longevity phenomenon is due to a number of factors that have coalesced to decrease the risk for both age-associated disease and mortality among older people. For example, there appear to be important genetic aspects to Okinawan longevity (7,37,38) that merit further investigation. The traditional diet, low in calories but high in nutrition, may have also led to a population-wide caloric restriction phenomenon, among other dietary and lifestyle factors (8,39–41). A superior public health system and other social and psychological factors may have also contributed to this longevity phenomenon (32). These factors deserve further investigation. Discovering the basis for the longevity advantage in Okinawa may have important potential implications for human health.

.... Centenarians are a valuable resource for the study of factors associated with exceptional longevity and healthy aging (7). However, most centenarian studies take place in European or North American countries, and few studies include minorities. As an ethnically distinct, isolated population of Japan with a very high prevalence of centenarians, a long life expectancy, and a highly functional elderly population, the Okinawans are an important population for studies of the genetic and environmental correlates of exceptional longevity. Further study of this population is warranted.