Reduction in mortality at advanced ages

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Citation: Kannisto, Vaino, Lauritsen, Jens, Thatcher, A. Roger, Vaupel, James W. (1994) Reduction in mortality at advanced ages. Population and Development Review (Volume 20) (RSS)
Internet Archive Scholar (search for fulltext): Reduction in mortality at advanced ages
Tagged: uw-madison (RSS), wisconsin (RSS), sociology (RSS), demography (RSS), prelim (RSS), qual (RSS), WisconsinDemographyPrelimAugust2009 (RSS)

Summary

The authors show that death rates have decreased among the oldest-old (80+) in 27 developed countries. The proportionate increase in oldest-old is greater than the increase in over-all population size from 1950 to 1990. Mortality decreases are attributed to death reduction after 80 as well as at younger ages. Mortality improvement has happened faster for females than males in all countries. However, rates of mortality improvement accelerated over the 1900s for men, women, 80 yos, and 90 yos. Rate of improvement is NOT highly correlated with mortality rate. Variation in the death rate 80-99 increases from 1950-1990. If these countries were approaching a "uniform mortality limit," the variation would decrease. The authors propose a "plastic" model of aging rather than a model in which mortality increases exponentially with age (Gompertz) and death is set to a biological clock. Another summary: Introduction: "Many gerontologists and demographers believe that death rates at advanced ages cannot be substantially reduced. Most deaths after age 80 are taken to be natural, senescent deaths due to intrinsic, intractable aging processes" (p. 793). Kannisto et al use data from a major university in Denmark to test this view of aging. Methods: Data are from the Kannisto-Thatcher Oldest-Old Database, which is housed at the Medical School in Odense University, Denmark. Population and death counts for 27 nations (all developed, although Eastern European nations to introduce some heterogeneity) were assembled by age (80 and over) and time. The "extinct cohort" method was used to compile death counts. A variety of simple analytic techniques were used, such as scatterplots and trend graphs. Findings: With the exception of some eastern European countries, every nation experienced mortality reductions for ages 80-99 from the 1960s to the 1980s. "In all of the countries examined, rates of improvement have been greater for females than for males: for ages 80-99 combined, the median annual gain has been 1.3 percent for females and 0.7 percent for males" (p. 798). However, the annual rate of improvement for males between the 1960s and 1980s declines only slightly with advancing age (about 9% annual reduction, for every age between 80-98). Conversely, for females "the rate of improvement falls from a much higher level of close to 1.8 percent at age 80 to converge with the level for males after age 95" (p. 798). Importantly, "If mortality among the oldest-old were approaching biological or practical limits, then countries that have the lowest death rates would be closer than other countries to such limits. Rates of mortality improvement, however, are only weakly [and negatively!] related to levels of mortality" (p. 802). Moreover, mortality levels are not converging toward some biological "maximum" among different nations. Rather, variability in mortality levels increased between developed nations from the 1950s to the 1980s. Finally, improvement in mortality may be summarized by the proportion of 80 year-olds who survive to age 100. In England and Wales, this proportion increased for males from .9 per thousand in the 1930s to 5.2 per thousand in the 1980s; for women, from 2.9 to 18.9 per thousand-both sixfold increases. Discussion: This study, in addition to several others, documents decreases in mortality at advanced ages. "Furthermore, recent research on nonhuman species undermines several long-held views: (i) there is a single, universal process of aging, (ii) that this process results in an exponential increase in mortality with age, (iii) that 'like a clock' every individual 'is constructed to run a certain time,' and that (iv) species have specific lifespan limits" (p. 804). "At current mortality levels a newborn girl in most developed nations has a life expectancy of about 80 years. If improvements in death rates could be maintained at an average rate of 1 percent per year, then her life expectancy would be about 90 years. Sustained 2 percent progress would imply that the typical newborn girl today in developed countries will live to celebrate her 100th birthday" (p. 805). If 2 percent reductions were achieved, the population above age 85 would explode from 3 million in 1990 to over 70 million in 2080. Compare this to the "high" projection of the Social Security Administration of 26 million! Kannisto concedes that current trends may not continue, but argues that continued progress is not implausible since (1) rates of mortality improvement at advanced ages have accelerated in recent decades, (2) rates of improvement in countries at low levels of mortality has been roughly on par with rates of improvement in countries at higher levels of mortality, and (3) death rates in different countries and between males and females have not converged over time. All three factors suggest that a biological "maximum" may not exist.