|6 Years Added to Life
The end result of mortality decline is most properly measured in years added to life. The number of years lived at each age is given by the life table function LX which represents the stationary population. The number of years added to life from one period to another equals the increase in LX per person and is shown in Figure 4 by sex and 5-year age group separately for each stage of transition.Figure 4. Years added to life by age and sex at different stages of transition.
The second stage was very successful in adding young years to life. For males the greatest gains were made before age 20 after which they were gradually frittered away as the death rate in middle age resisted decline and even increased. Nevertheless, as the children saved from death lived on, the transformation which took place was essentially a gain for adult age: a mean age of 35 for men (Table 4). For females, in contrast, further gains were accumulated through middle age, leading to a peak at 60 years, although the mean was 43.
In the third stage the dramatic fall in death rates produced smaller gains in childhood and youth because of the already lower level of mortality. Instead, the gains kept increasing vigorously through middle age as a result of successful control of tuberculosis and many other diseases and infections. The years added to life were centered in middle age (46 for males, 50 for females) and continued up to old age. Among males, in particular, many more years were added to old age than during the long second stage.
The characteristic feature of the fourth stage of transition has been a decline in the mortality of the elderly and even the very oldest. In infancy and childhood, in spite of the still continuing rapid fall in death rates, relatively few years were added to life and to life expectancy. The gains were instead pushed to ever older age groups. It deserves attention, though, that men have now, belatedly, received great benefits already at ages 50 to 70. The impact of delayed ageing has altogether been felt by men at younger ages than by women, the peaks being observed at 70-74 and 80-84 years respectively while the mean age of the added years was 65 for men and 67 for women. For the first time ever, very substantial gains in survival can be noted even above age 90. On the other hand, however, the precipitous fall of the curves on the right testifies to increasing resistance to prolongation of life close to age 100.
The relative age distribution of the years added to life (Table 4) provides some concise indicators of the development during the different stages. The great gains of the second stage were relatively evenly distributed to males of all ages but with a slight tendency to older ages among the females. The remarkable fact about the third stage was the great benefits it still gave to working ages. The fourth stage has been subject to diminishing returns for the young and middle-aged, with a corresponding expansion for the elderly on whom any further increase in life expectancy at birth will depend. The mean age of years added to life increased slowly through nearly a century of transition but made a quantum leap during the fourth stage.Table 4. Age distribution and mean age of years added to life during each stage of transition.
While the first three stages of transition reduced premature mortality, the uniqueness of the fourth stage as illustrated in Figure 3 and Figure 4 and in Table 4, lies in moving the inevitable end of life to a higher age. The earlier stages saved lives, the fourth one delays death.
This opens new vistas for the extension of human life for which considerable scope is seen to exist. On the other hand, gains made in survival have been progressively smaller at higher ages portending a likely slowdown in the future. A projection of the mortality decline of the last 20 years in a group of 13 low-mortality countries up to year 2050 indicates that the modal length of life would then be 92 years for females and 85 for males. Because of some inevitable premature mortality, the life expectancies at birth would be somewhat shorter .
Unprecedented and imprevisible developments may of course change the scenario either by prolonging life through scientific breakthroughs or by shortening it by deterioration of the environment or appearance of new diseases or more virulent forms of old ones. Any of these modalities would mean a new, fifth stage in mortality transition.
|Finnish Life Tables since 1751
Väinö Kannisto, Oiva Turpeinen, and Mauri Nieminen
© 1999 - 2000 Max-Planck-Gesellschaft ISSN 1435-9871