Developing Models of Longevity
Hagberg, Bo, Annual Review of Gerontology & Geriatrics
Bernard Jeune, in Centenarians-the Secret of Tales (1994), made the following statement:
Due to a demographic shift to the right of the survivorship distribution there has developed a new historical phenomena, a proliferation of centenarians. As the numbers of centenarians are increasing, there is a doubling rate in most population of about ten years, more and more researchers are taking up the study of extreme longevity, (p. 4)
The research question that we all want the answer to is, of course: What is the secret of a long life? What can we learn from the extreme survivors? Is it possible to construct a model and eventually a theory that explains or helps us to understand the mechanism behind longevity? This chapter presents a tentative model explaining longevity as a result of a lifelong psycho-physiological interaction.
One of the criteria for such a model is to explain the great variation in behavior and functional capacity that is found among the elderly and that seems to increase with age. Jim Heynens wonderful expose One Hundred Over 100 details the lives of 100 centenarians and notes:
Its not true that only short, skinny people live to be old; several people here are over six feet tall and some weighed 245 pounds most of their lives. Its not true that genetics is the sole determiner of who will live to be old; several people here are breaking all family records. Its not true that only the carefree non-worriers live to be old, some people here have always been worry warts. There are health nuts that might be viewed as early pioneers in the field of life extension but there are also a surprising number who are addicted to tobacco. Retiring early because of a nervous breakdown? You're in here. Lonely and childless? You're in here in abundant numbers. Recovering from cancer? You have many partners, some who have recovered from cancer three times. (Heynen, 1990, p. xiii)
And so the stories continue to exemplify the differences among people who reach very old age. Heynan concludes, "once and for all, you should be assured there is no one formula, no single secret. If there is a secret there must be at least 100!" (Heynen, 1990, p. xiii). At the end of their life story review, they are all asked the same question, "How did you get so old?" The remarkable thing is that they all give different answers. James Holy Eagle says: "Don't worry; that will get you old very quick." Johanna Pedersen says: "Work, work and work, but you have to love your work." John Hilton says: "Regular hours for everything." Peter Spaan says, "Just luck." Or as Jeanne Calment, 122 years old, expressed herself, "I have taken an interest in everything and had a passion for nothing."
There is a primary lesson about aging to be learned here: At 100 years, the only trait the centenarians seem to have in common is advanced age; otherwise, they differ in most ways. Very old persons differ in the way they behave, how they think, in their living conditions and living arrangements, in their functional capacity, but especially in their life stories and life experiences. That poses a serious question to any scientist who wants to formulate general laws, theories, or models to understand the mechanisms behind longevity and survival-not only to a long life but a long and a good life (i.e., aging well). How do we arrange the multitude of facts that seems necessary to understand or explain aging as it is expressed in exceptionally long lives?
Obviously, a number of problems must be addressed to develop a plausible statement about how longevity is achieved: multidisciplinary determination, multifactor combination and aggregation of data, and multiple variables in interaction. Furthermore, we have to consider how to handle multiple perspectives, diverging theoretical starting points and assumptions, as well as methodological techniques to handle complex data setups. Added to these considerations is the question of whether the baseline age used in research affects the predictors of survival/longevity. …