Other Free Encyclopedias » Medicine Encyclopedia » Aging Healthy - Part 3 » Longevity: Social Aspects - Survival Curves, Rectangularization Of Mortality, Mortality By Cause, Longer Lives And Better Health, Factors Related To Mortality

Longevity: Social Aspects - Rectangularization Of Mortality

age age life ages survival

Note the changing shape of the survival curves with time (Figure 2). From 1900 to the present, the survival curve has become more rectangular due to increased survival at all ages, but especially at the young and middle ages. To describe the changing shape of the survival curve over time, Fries coined the concept "rectangularization of mortality."

Debate centers around future reductions in mortality and whether there is a limit to the human life span. Fries argued that while continued improvements will occur at the younger ages, we have witnessed most of the possible mortality improvements at the oldest ages. But based on current survival curves, there is still ample room for improvement in the fifties, sixties, and seventies.

Fries also suggested that greater proportions of individuals will survive to age eighty-five, with few individuals surviving beyond this age. Similarly, Olshansky and others asserted that life expectancies Table 1 Percentage survivors by age, United States, various years SOURCE: Adapted from: Murphy, S. L. "Deaths: Final Data for 1998." Monthly Vital Statistics Report 48 (2000): 1–108. Also from: Anderson, R. N. "United States Life Tables, 1998." National Vital Statistics Reports 47 (2001): 1–38. will continue to increase, but at a slow pace, noting that even though mortality has declined for older age groups, neither the right tail of the age distribution nor the age of the verified longest-lived individual has substantially increased. Newer evidence, however, suggests that the survival tail will continue to lengthen. Indeed, there have been noticeable changes in the percentage of individuals in the United States and other countries surviving to the ages of ninety-five, one hundred, and beyond. Some researchers also raise the possibility of much higher future life expectancies, with more and more individuals living to one hundred and beyond (see National Research Council).

It seems reasonable to consider that the life span is not fixed, and can be extended through incremental advances. For example, if life span is currently 122 years and 165 days based on the documented length of life of a French woman named Jeanne Calment (National Research Council), then it seems reasonable for other individuals to live the same length of time plus one day, and so on. In fact, at the oldest ages, mortality has declined and the distribution of ages of death has lengthened for more than a century. From 1870 through 1990 in Sweden, a country with excellent documentation of births and deaths, the oldest reported age has increased about one year for every twenty years of time (Wilmoth and Lundstrom 1996).

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