Mortality, Epidemiological, And Health Transitions Research Paper

1. The Mortality Transition

The mortality transition and the fertility transition together make up the so-called demographic transition. This term is used to describe the historical process whereby fertility and mortality rates declined from the high and approximately compensating levels that they exhibited in past times to the low and approximately compensating levels that they exhibit in rich countries today, with the intervening period generally exhibiting higher rates of population growth than occurred in either the earlier or later periods because mortality rates tended to fall before fertility rates. The intermediate period has tended therefore to be one of marked population increase.

The Western-bloc countries of Europe, the English-speaking countries (the United States, Canada, Australia, and New Zealand), and Japan now enjoy the longest life expectancies ever recorded. Japan appears currently to be leading the field, with the most recent official statistics (for 1993) suggesting an average life expectancy exceeding 82 years for women and 76 years for men (United Nations 1996). Apart from Japan, countries with life expectancy at birth for females of 80 years or more include (in declining order) France, Australia, Sweden, Norway, and the Netherlands; those with life expectancies for men of 74 years or more include Sweden, Australia, Norway, the Netherlands, and Singapore. These figures represent increases in life expectancy of about 25 years over the last century (Preston and Haines 1991).

It is salutary to recall that past levels of infant and child mortality in today’s low-mortality countries were brutally high. It has been estimated, for example, that not until the early eighteenth century did fewer than 30 percent of children of the Genevan bourgeoisie die within the first five years of life, and not until the middle of that century did fewer than 20 percent die (Hill 1995), yet at the same time in France the comparable proportion dying was close to one-half (Vallin 1991). In 1780 in Sweden almost one-third of children died before they reached their fifth birthday; this proportion had fallen to about 23 percent by 1870, about 15 percent by 1900, and less than 3 percent by 1950 (Keyfitz and Flieger 1968). As we begin the twenty-first century, it is well under 1 percent (Keyfitz and Flieger 1990).

One interesting aspect of the historical mortality transition in the West is that its occurrence was not recognized at the time. Not until the beginning of the twentieth century, for example, was it recognized that mortality rates in Britain were really declining rather than just fluctuating, but the onset of decline is now placed a century and a half earlier, in the middle of the eighteenth century (Fogel 1997). Indeed, by the middle of the eighteenth century, mortality was declining not just in Britain but throughout northwestern Europe.

The discovery that the twentieth-century mortality transition represents the continuation—admittedly the most rapid—of a process that had started considerably earlier complicates the task of explaining what brought it about. Various studies attributed the mortality transition to public-health reforms, advances in medical treatment, improved hygiene, and rising standards of living, or a combination of these, but none of these explanations has escaped criticism (Fogel 1997). McKeown (1976), perhaps the best known of the critics, reacted in particular against claims that what had been most important were advances in medical treatment and improvements in public health. McKeown shows that death rates from respiratory tuberculosis, for example, declined steadily in England and Wales at least from the middle of the nineteenth century although the bacillus was identified only in 1882, effective chemotherapy was introduced only in 1947, and BCG vaccination used on a substantial scale only from 1954. McKeown makes similar arguments for other infectious diseases as well, showing that in England and Wales rates of death from pulmonary infections (bronchitis, pneumonia, and influenza) and, for children under 15, from whooping cough, measles, scarlet fever, and diphtheria were all falling before the causal organism was identified, and certainly before effective treatment or immunization was introduced. McKeown’s alternative suggestion was that the primary determinant of the mortality transition must have been increasing affluence which brought with it improved nutrition, but as Preston and Haines (1991) and Fogel (1997) have noted, and as McKeown (1978) himself admits, his arguments are both circumstantial and based more on the elimination of other factors that may have been important—through what Schofield and Reher (1991, p. 8) term a ‘rather liberal use of reductive logic’—than on demonstrations of improving nutrition and of a link between better nutrition and lower mortality.

Perhaps McKeown’s greatest contribution has been in stimulating closer examination of this issue. Interesting and persuasive cases have been made for the importance of improvements in water supply and sewerage (Preston and van de Walle 1978) and more generally of public-health measures designed to ameliorate living conditions in crowded urban areas (Szreter 1988), of the control of disease-spreading insects (Riley 1986), of improvements in housing (Burnett 1991), and, around the turn of the twentieth century, of improvements in domestic childcare (Preston and Haines 1991). Finally, the importance of improved nutrition has at last been demonstrated more directly. Improvements in nutritional status appear to explain about nine-tenths of the mortality decline in France and England between the last quarter of the eighteenth century and the third quarter of the nineteenth, but only about half of the decline between the third quarter of the nineteenth century and the third quarter of the twentieth (Fogel 1997). ‘Only half,’ however, is an impressive proportion, particularly given the progress that medicine made during this century, most significantly with the development of antibiotics and of vaccines for major childhood and other diseases.

In the earliest formulations of the demographic transition, in the 1940s and 1950s, the driving force behind the declines in both mortality and fertility was identified as modernization although this term, apparently in the belief that it was self-evident, was not defined. In addition, links were suggested between these declines: people were said to begin to limit the size of their families after they recognized that fewer of their children were dying and hence that they did not need to produce so many children in order to ensure a sufficient number of survivors.

With the growth of demography as a discipline and the proliferation of analytical methods and of collections of demographic data to which to apply them it has become clear that the reality is far more complex. Mortality decline has not always preceded fertility decline, for example, nor has fertility always declined after mortality did, and both declines have been observed in the absence of social and economic modernization. Thus, even if demographic transition remains ‘one of the best-documented generalizations in the social sciences’ (Kirk 1996, p. 361), it is also true that the demographic transition is both ‘less a theory than a body of observations and explanations’ (Caldwell 1996a, p. 175).

2. The Epidemiological Transition

Although proposed as a theory, the heart of Omran’s epidemiological (or epidemiologic) transition is probably best characterized, like the mortality transition, as an empirical generalization. The core proposition is that when mortality is high during ‘the age of pestilence and famine’ (Omran 1971, p. 516), causes of death are dominated by infectious and communicable diseases; then, after an intervening ‘age of receding pandemics,’ low mortality brings ‘the age of degenerative and man-made diseases’ (Omran 1971, p. 517). Analyses of more recent developments in mortality in the United States have led some observers to posit a fourth period, ‘the age of delayed degenerative diseases,’ during which the age at which degenerative diseases become lethal is postponed to such an extent that life expectancy is propelled into or even beyond the eighth decade of life (Olshansky and Ault 1986).

The developed market-economy countries, with the longest life expectancies in the world, exhibit what Omran (1971, p. 533) called the ‘classical or western model’ of the epidemiological transition. These are countries in which the transition, at least as originally formulated by Omran, is virtually complete. They may be contrasted with the developing countries, whose epidemiological transition Omran (1971) designated a quarter of a century ago as ‘contemporary’ or ‘delayed.’ In many instances, however, their subsequent mortality declines are now more accurately termed ‘accelerated’: the onset of mortality decline may have been delayed relative to that in the West, but the pace of subsequent decline in many regions has been more rapid than it was in the West. Indeed, some of the greatest success stories, as well as some of the greatest failures (as discussed below), have been registered in the developing countries.

Although no country in sub-Saharan Africa has failed to achieve at least some decline in infant and child mortality, this region remains the most resistant to intervention. The few apparent successes (such as Botswana) are counterbalanced by the experience of a large group of countries that have experienced disappointingly little decline at all (such as the former Zaire). Of 15 countries for which child-mortality estimates were available in 1985 four had a probability of child mortality of 200 or more per 1,000 (i.e., at least 200 out of 1,000 children did not survive to their fifth birthday), six were in the range 150–199, three were in the range 100–149, and only two fell below 100 (Ewbank and Gribble 1993).

These levels, and the life expectancies they imply can be interpreted in different lights. One view is that there has been progress. Thus, Preston (1995, p. 34) observes that Africa’s regional life expectancy of 52 years ‘would have been the envy of Europe at the turn of the century.’

Another view is that progress has been slow. Vaccines exist for measles, diphtheria, whooping cough, tetanus (the latter three being combated with DPT vaccine), and tuberculosis, but these diseases, and especially measles, still remain major killers of Africa’s children (as does tuberculosis of her adults) (Ewbank and Gribble 1993). Except for smallpox, for which vaccination was available already in the nineteenth century, Europe exhibited her ‘African’ levels of child mortality when there were neither vaccines to prevent the major childhood diseases nor modern drugs, most importantly antibiotics, with which to combat them. Where child mortality has fallen in sub-Saharan Africa it is largely because of public-health programs, notably the World Health Organization’s Expanded Programme on Immunization, no parallel version of which existed in Europe at the turn of the century.

It would be wrong to give the impression that among the developing regions it is primarily sub-Saharan Africa where these diseases remain to a greater or lesser extent resistant to attempts at intervention, and where reduction of mortality continues to pose a difficult problem. High levels of infant and child mortality still prevail in much of South Asia, especially Bangladesh, and also in Southeast Asia, especially Indonesia.

It would also be wrong to give the impression that the major problem in these regions is early mortality. Rather, these are regions that suffer not just from high mortality but from poor data, especially on adults. Demographic surveys, as they have developed since the 1970s through the experience of the 40-odd national fertility surveys of the World Fertility Survey, and from the mid-1980s to the present with the even broader coverage of the Demographic and Health Surveys, have become increasingly good at measuring the mortality of children from information supplied by their mothers, but in the absence of good systems of vital registration in the vast majority of these countries, or of reliable ways of estimating adult mortality by more indirect means, too little is known about the mortality of adults in most of the countries that are classed as ‘developing.’ One can say only that it is too high. In many countries the evidence for this is that causes of adult death are still dominated by infectious and communicable diseases: that people do not yet have the luxury of surviving such diseases for long enough to succumb to the degenerative ones.

While the epidemiological transition is generally described in terms of declining mortality’s being associated with a shift in the disease burden, one can reverse the description and say that as the burden shifts from infectious to degenerative diseases, mortality falls. This re-statement highlights a number of important considerations. One is that death rates from infectious diseases are capable of reaching levels far higher than those ever achieved by degenerative diseases and neoplasms. Although extremely high levels of mortality are not sustainable for extended periods since survivors of infectious diseases may be better equipped to withstand the next onslaught, and since diseases themselves die out if they kill all their hosts, the mortality rates experienced by pre-transitional populations, particularly in years of severe epidemics, are strikingly high. Indeed, one of the features of the epidemiologic transition and, indeed, of the mortality transition, is a pronounced reduction in the variability of death rates from year to year (Schofield and Reher 1991, Fogel 1997).

Another consideration is that, although infectious diseases can be lethal at any age, their effects tend to be particularly virulent among the young. In contrast, the major targets of degenerative diseases are older people. Reducing the mortality rate from an infectious disease is likely therefore to have a much more pronounced effect on overall mortality than would reducing the mortality rate from a degenerative disease because, given the characteristic shape of the population pyramid, there are more people at risk of death from an infectious disease than from a degenerative one. Moreover, the effects of such a disease shift are not confined to mortality rates since infectious diseases eliminate a proportion of the very young who would otherwise go on to bear their own children, but degenerative diseases affect those who have started, or even completed, their own families. In illustration, Keyfitz (1977) has shown that even when approximately the same number of deaths occur from malaria and heart disease, eliminating malaria has four times the effect on subsequent population increase as eliminating heart disease.

3. The Health Transition

Dissatisfaction with the gains from conventional demographic investigations of mortality and mortality change led to the coining of a new term, health transition. The use of the word ‘health,’ which was deliberate, signaled a commitment to focus not just narrowly on death and illness but more broadly on the positive state of health and well-being, an altogether larger condition than survival or even the absence of ill-health; while the use of the word ‘transition’ was intended to carry echoes of demographic transition, mortality transition, and epidemiological transition. The term ‘health transition’—‘the changes over time in a society’s health’ (Caldwell 1996b, p. 356)—might seem self-explanatory and, indeed, is used by some researchers as a virtual synonym for the mortality transition. Nevertheless, as originally formulated, the term was meant to refer also to the determinants of changing health and, in particular, the cultural, social, and behavioral determinants. Health-transition research therefore does not necessarily have at its core a collection of empirical data (although, this being said, most analysts support at least some of their arguments with standard demographic measures). Rather, the research seeks to explain how cultural, social, or behavioral factors have contributed to a particular health situation, whether static or dynamic, and frequently concentrates on a search for determinants of health improvement that may be susceptible to intervention. The reasons for looking beyond strictly medical and economic conditions are twofold. First, these two areas have already received a great deal of research attention. Second, the policy implications of research that finds a beneficial effect on health of an increase in a country’s health budget or its industrial or tertiary sector is in many cases likely to be of limited practical importance.

A major stimulus to the growth of health-transition research was Caldwell’s (1986) article that attempted to explain the mortality transition that had occurred in Sri Lanka, Costa Rica, and the state of Kerala (which is in population terms as big as many countries). Each population remained poor, nor was public expenditure on the provision of medical services such as to preclude emulation by other societies at a similar level of economic development. What these very different populations shared was a respect—indeed a demand—for education, a relatively high degree of female autonomy, a fairly open society, and a tradition of government intervention to improve both health and nutrition. In suggesting the possibility of improved health and lower mortality in societies that have not passed through the economic and social transformations experienced by contemporary low-mortality countries, this and other key pieces of research have directed the attention of a sizeable group of researchers back to the beliefs, attitudes, and behavior of the individuals whose collective experience is ultimately reflected in morbidity and mortality statistics.

4. Three Transitions Or One?

In considering what is meant by the mortality transition, the epidemiological transition, and the health transition the question arises of whether the approaches they imply are best viewed as distinct or as complementary. The question is important because the framework in which past and contemporary developments in population health, ill health, and mortality are viewed is likely to dictate the form of analysis, and hence the form of its conclusions. The framework of the mortality transition is likely to emphasize the identification of trends in mortality rates, of differences between rates that obtain in different populations, or of heterogeneity in rates within a population. That of the epidemiological transition is likely to stress the contributions of shifts in different causes of death to shifts in overall mortality, or even to concentrate solely on the evolution of rates of death according to a particular cause. Finally, the health-transition approach is likely to focus more closely on the role of individual agency, and to broaden the field of investigation from death, disease, or ill health to beliefs about health and illness, attitudes to modern preventative and curative health services, and social or cultural barriers or enabling factors that variously inhibit or promote the use of such services.

Despite the fact that the three approaches appear to be distinct, it can be difficult to state categorically which one of the three is best suited to the investigation of a particular research issue. Take, for example, work on within-population heterogeneity in the risk of death. Well before the advocacy of the health-transition approach, researchers had recognized that mortality rates varied according to socioeconomic characteristics either, in the case of adult mortality, of the individuals themselves or, in the case of infants and children, of their parents. Indeed, even Omran (1971, p. 527), whose description of the epidemiological transition is most usually interpreted as referring merely to a shift in causes of death as mortality rates fall, proposed that the shifts in patterns of health and disease that characterize the epidemiological transition are ‘closely associated with the demographic and socioeconomic transition that constitute the modernization complex.’ More recently, Mensch et al. (1985, p. 286) concluded that ‘membership in a social group that is more advantaged or more modern is associated with lower child mortality, whether the variable of interest is education, income, urban residence, housing type, father’s occupation, or one of the many other variables examined.’ Many of the characteristics that were identified as associated with lower child mortality have been the focus of subsequent research that can probably best be described as falling within the health-transition framework. The difficulty is that a large-scale demographic sample survey or census is a good vehicle through which to identify the existence of heterogeneity in the chance of survival, but it is ill-suited to explaining how such heterogeneity has been created. Conversely, a smaller investigation that employs a variety of data collection techniques, probably involving considerable direct participation by the principal investigators, is a good vehicle through which to understand the immediate determinants of individual health-enhancing behavior, but is ill-suited to quantifying the extent to which different forms of individual behavior lead to different health outcomes.

For people who would wish to apply research findings to health policy this distinction is of more than academic significance. A study of the former type, involving quantitative analysis of a large-scale demographic survey, perhaps identifies maternal schooling as an important correlate of child survival, and reports that ten years of schooling is associated with an average reduction of child mortality of one-third. But what is the policy implication? A huge injection of (possibly scarce) government funds into mass education, especially for girls? Conversely, although a study of the latter type, involving close analysis of the pathways that individuals follow in the quest for health, can result in no such dramatic statistic, it may reveal something about how maternal education operates to improve child survival. It may tell us, for example, whether what is most important is having grown up in a family that bothered to send its daughters to school, or the actual experience of having gone to school, or the confidence instilled by the experience of schooling, or the content of what was taught, or simple literacy. The implications for health interventions of each of these would be very different.

It is likely, then, that the studies that will be the most revealing and certainly the most useful to the makers of health policy are ones that combine the different approaches (see also Cleland and van Ginneken 1988). Moreover, despite the fact that most research that explicitly declares itself to fall under the health-transition rubric is concerned with health in the developing world, the quest for a better understanding of the behavioral and social determinants of health is a worthwhile endeavor in any population, whatever its mortality statistics. An obvious candidate for such investigation is that of the recent reversal of the mortality transition in the countries of the former Soviet bloc, most notably in Russia herself. Another is that of the widening gap between the death rates of manual and non-manual workers in Sweden, the country where it was believed until recently that mortality differences according to social class probably no longer existed (Vagero and Lundberg 1995).

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