12. Gender and mortality
Almost all modern data available anywhere on the subject show the human female to have a longer life span than the male, and the exceptions to this rule arise from unusually harsh living conditions for women. This female superiority in survival is very strongly manifest in old age where, therefore, as age advances, women outnumber men in an ever-increasing ratio.
This is also the case in the countries of the database. On the other hand, critical evaluation of the data have shown that where age overstatement occurs, it was always more serious for men. This male preponderance for age overstatement may obscure the true situation in poorly documented populations. Table 25 gives four gender indicators of mortality derived from probabilities of dying in the group of thirteen countries in 1980-90. The data are for single years of age but beginning with age 98, they were averaged over 3-year age periods. As the averages for 104-106 are often out of line with the rest, they should be considered tentative. The corresponding data for earlier decades are given in Annex Table 9.
The four indicators give the following account of the situation:
1. Sex ratio of mortality, also called excess male mortality, is obtained by dividing a male mortality indicator (q or m or other) by the corresponding female indicator. It is the most commonly used measure of relative mortality of the sexes. Frame 1 in Figure 24 shows how the ratio tends to decline with age and how in the postwar era, this fall has become more abrupt as the male excess has more than doubled at age 80. The form of the curves suggests convergence of the male and female mortality at high ages. Such a conclusion, however, does not stand the test of the following indicators.
2. Sex differential in mortality is the absolute difference of the male and female mortality parameters. Frame 2 shows that this indicator is fairly constant over the age range and that its increase over time has been quite small. What deserves emphasis is that there is no sign of convergence of male and female mortality as was suggested by the sex ratio, except perhaps among the older centenarians.
3. Sex ratio of survival equals the female parameter divided by the male and is therefore a figure normally larger than one. This ratio increases slowly with age, its level slightly higher in each successive decade. More stable by age and over time than the sex ratio of mortality, this may be a better indicator of the gender factor at high ages.
4. Female age delay in mortality tells at how much older age the female parameter equals the male parameter of a specified age. This indicator is therefore akin to the age shift discussed in Chapter 8. In 1950-60, the age delay was very steady at 2 years at all ages until it became volatile with decreasing numbers of observations at high ages. Since then, it has increased at age 80 to exactly 4 years due to the rapidly declining mortality of women at these ages. From this high level, the indicator now declines and reaches around age 90 the former 2-year level. It is a property of this indicator that it does not measure the mortality of the two sexes against a neutral mathematical standard but against each other. If a population has its own characteristic age pattern of mortality, then this indicator can be considered the most suitable one to measure the gender factor.
The observations above leave open the question of whether the female advantage in survival lasts to the highest ages. Three of the four indicators seem to register a sudden drop towards unity by age 105, a drop so abrupt as to raise doubt about its reliability. At these ages, where the number of observations is not large, greater stability is found in survival rates of longer term. Table 24 in Chapter 11 gives for 1980-90 in the age span 100-105 a sex ratio of survival 1.38, and for 105-110, a ratio of 1.88. Another strand of hard evidence is the number of supercentenarians in the thirteen countries: before 1980, there were 2 men and 15 women, after that date, 4 men and 35 women. These facts suggest that the female advantage last till the highest ages.
The four gender indicators presented above describe the situation and its development from different angles, and each of them has a justification. The nearly exclusive use of the first indicator by demographers is understandable regarding young and middle age where death rates are low, deaths largely preventable and their causes relatively well definable. This situation begins to change subtly with the onset of old age. First, there is a question of simple mathematics. At death rates of 1 or less per 1000, the sex ratio of deaths may amount to several integers but when the death rate reaches 400 per 1000, this is no longer possible. To observe that the sex ratio of mortality declines with age, is stating the obvious.
As age advances, a person's fate depends less and less on the action of forces of death outside him and increasingly on the waning force of life in himself. BOUGEOIS-PICHAT (1953) saw here endogenous causes of death gradually prevailing over the exogenous. At the same time, death rate rises to levels where its complement, the survival rate, becomes a useful demographic tool. At high ages, therefore, the forces of life and death may be more appropriately measured by the rate of survival which stands for the force of life. The greater stability of the sex ratio of survival in Figure 24 supports this view. The characteristics of these and other mortality parameters will be further discussed in Chapter 16.
For an international comparison of the gender factor in old age mortality we present in Table 26 two summary indicators which together perhaps give a fair overall appraisal of it, namely the difference in life expectancy of the sexes at 80, and the age difference by which the female death rate trails the male death rate, termed female age delay. This latter is given in the table as the mean delay from male mortality at ages 80-94. Altogether, 25 countries are listed because these gender indicators were found plausible for several countries where data quality generally is somewhat uncertain.
The difference in life expectancy varies from one to just short of two years. At the top are countries of medium or low mortality but not those of lowest (Iceland and Japan). Clearly, when males are far behind, the average for the two sexes is affected. The smallest gender differences in life expectancy are found in the former East bloc and also in Southern Europe.
The age delay indicator, measuring the gender difference in terms of the mortality pattern peculiar to each country, gives a somewhat different picture. The two indicators are juxtaposed in Figure 25 and reveal remarkably enough that the four Anglo-Saxon countries have the largest sex differences when measured in their own terms. The smallest differentials are found in countries with not very reliable data (Latvia, Poland and Spain) but also generally in Eastern and Southern Europe.
At ages 80-84, the female age delay is usually between 2.5 and 4 years and thereafter tends to decline to around 2 years by 90-94, a tendency which has a moderating effect on the overall female advantage. When this does not happen, as in Scotland, the gender difference in mortality is strengthened.
The wealth of evidence in this and other studies definitely supports the view that in societies which do not seriously discriminate against either sex, the females tend to live longer than the males. As this must be a genetic factor, result of evolution, it is almost certainly present in all human populations today.
The recent, relatively greater progress by females is, however, subject to period factors and may not continue in the future. Due to a gradual effect of increased smoking by women while smoking by men has decreased, the sex ratio in lung cancer mortality at ages 65 - 74 declined in many countries of Northern and Western Europe between 1979 and 1987 (WALDRON 1993).
Updated by V. Castanova, 1 November 1999