The influence of cause-specific mortality conditions on the age pattern of mortality with special reference to Taiwan

Abstract This paper discusses the relationship between the level of mortality at ages one to four, on one hand, and five to 34 on the other. This relationship has been observed to vary considerably among mortality schedules at different levels of mortality and even among schedules at the same general level of mortality. This variation is shown among the modem life table systems of the Regional Model Life Tables and the United Nations Model Life Tables. Controlling for the leyel ofmortality from age five to age 34, the West Tables and the United Nations Tables embody approximately the same 'average' relationship between early childhood and adult mortality. Relatively to this average relationship, the South and East Tables consistently display higher childhood mortality rates for a given level of adult mortality. Indeed, the childhood rates of the South Table are twice those of the West Tables over a range of life expectancy at birth from 40 to 70 years. The relationship between childhood and adult mortality from 1957 to 1968, a period of rapid mortality decline, was investigated in Taiwan. In 1957, the Taiwanese data reflected the severe childhood mortality of the South Model Tables. However, by 1968, due to an especially large decline in childhood mortality, this relationship was more moderate and resembled the mortality pattern of the West or East Model Tables. An analysis of the decline in cause-specific mortality during the period revealed that a dramatic decline in childhood mortality from gastro-enteritis was primarily responsible for the shift in the relationship between childhood and adult mortality in Taiwan. It is asserted that, while any of several diseases which result in fatalities primarily among children of pre-school ages, could cause relatively severe childhood mortality, gastro-enteritis is likely to be a primary contributor to such an age pattern. This assertion is based on the fact that, especially in the developing areas of the world, malnutrition and gastro-enteritis are usually precipitating and complicating factors of other childhood diseases. A limited test of this hypothesis was provided by considering the causal components of childhood mortality rates in two populations known, for certain periods, to have exhibited relatively severe childhood mortality conditions; Spain and Portugal. For the years in which those populations were characterized by the South mortality pattern, gastro-enteritis was a principal cause of mortality in childhood. Moreover, with the decline in mortality from gastro-enteritis, the mortality pattern in Spain and Portugal no longer exhibited childhood mortality rates which were severe relative to those of adult life. The implications of these findings for the analysis of mortality conditions in many areas of the developing world, where the gastro-enteritis malnutrition syndrome annually claims a heavy toll of life in early childhood, are not clear. In those areas, the effect of this syndrome on the age pattern of mortality could be offset by special conditions inflating adult mortality rates. Nevertheless, in circumstances where there is evidence indicating substantial childhood mortality from this syndrome and no evidence indicating compensating severe adult mortality, there is reason to suspect that the existing mortality pattern reflects the relatively severe childhood mortality conditions of the South Model Tables. Additionally, where mortality from the gastro-enteritis malnutrition syndrome has been severe in past years, but has been reduced to low levels in recent years, it is probable that the relationship between childhood and adult mortality will shift in favour of the former - quite possibly, in the manner of Taiwan, from a South to an East or West age pattern.