Epidemiologic transition theory e...
Epidemiologic transition theory exceptions Graziella Caselli*, France Mesl��** and Jacques Vallin** *Dipartimento di Scienze Demografiche Rome1 **Institut national d'��tudes d��mographiques, Paris2 Introduction Abdel Omran���s 1971 theory of epidemiological transition is an attempt to account for the extraordinary advances in health care made in industrialized countries since the 18th century. According to Omran, all societies experience three "ages" in the process of modernization: the "age of pestilence and famine", during which mortality is high and fluctuating, with an average life expectancy under 30 years the "age of receding pandemics", during with life expectancy rises considerably, from under 30 to over 503 and the "age of degenerative and man-made diseases", during which the pace of the mortality decrease slackens, while the disappearance of infectious diseases increases the visibility of degenerative diseases, while man-made diseases become more and more frequent. At the time Abdel Omran was developing his theory of epidemiologic transition, the most competent specialists, along with United Nations experts, saw life expectancies as generally converging towards a maximum age, the most advanced countries seeming very close to it. According to the United Nations World Population Prospects, the point of convergence was 75 years (United Nations, 1975).. And as things now stand in the most advanced countries, the increase in life expectancy has slowed down since the 1960s and in some countries has even halted, in particular as concerns men. The "cardiovascular revolution" of the 1970s launched a new period of progress. However, Jay Olshansky and Brian Ault (1986), followed by Richard Rogers and Robert Hackenberg (1987), without criticizing the basic premises of the theory of epidemiologic transition, introduced the idea of a "fourth stage"4 during which the maximum point of convergence of life expectancies would seem to increase thanks to achievements in the treatment of cardiovascular diseases. Jay Olshansky et al. (1990) set this new maximum at 85 years, the same as that chosen by the United Nations at the end of the 1980s for all countries (United Nations, 1989). 1 Via Nomentana 41, 00161, Roma, e-mail : email@example.com 2 133 Bd. Davout, 75980 Paris cedex 20. E-mail: firstname.lastname@example.org and email@example.com 3 See also Caselli (1991) for a description of epidemiologic changes in Europe at the turn of the 20th century. 4 Olshansky and Ault: "A fourth stage of the epidemiologic transition". The others refer to a "new" or "hybristic" stage.
2 Today, the 85-year threshold is strongly criticized by many authors who believe that such a limit cannot be determined (Barbi et al, 1999 Vaupel, 2001 Carey and Judge, 2001). However, our aim in this article is not to discuss this aspect of the epidemiologic transition, but to study the numerous exceptions observed since the 1960s in the general trend of increasing life expectancy. Not only have many countries (in particular Eastern European countries) lacked the means to experience the "cardiovascular revolution", but a number of others, especially in Africa, have not yet completed the second phase of the epidemiologic transition and are now hard hit by the arrival of new epidemics such as AIDS, or by the reemergence of older diseases. After a brief overview of the first "disruption" of the 1960s, which put an end in the advanced countries of the North to the convergence observed in previous decades, and of the second failure which affected countries of the South, in particular due to the AIDS epidemic, we will see that the fact that Africa has lagged behind the North can be interpreted as a failure to complete the second phase of the epidemiologic transition in the third part of this article, we will examine the reasons why Eastern Europe has failed to enter the fourth phase. I. From convergence to divergence At the time Abdel Omran was developing his theory of epidemiologic transition, events seemed to justify his views. The least-developed countries, in full transition, were gaining control over infectious diseases, and they seemed to be rapidly catching up with the most advanced countries these, for their part, seemed to have reached a threshold, since the incidence of infectious diseases had been so far reduced that any further reduction could not represent any significant gain in the average life expectancy. What was most feared at the time was that some of these gains in life expectancy might be lost due to the increase in man- made diseases 5��� caused by smoking or car accidents, for instance these dangers seemed more probable than the prospects of new progress in fields then thought to be governed by the inevitable degeneration of age, such as cancer and cardiovascular diseases. Thus, towards the end of the 1950s, life expectancy in the United States had reached a threshold of about 70, and Russia and Japan were close to reaching that level (see Figure 1). What Omran's theory could not foresee was that the rise of man-made diseases would be curbed by efficient policies, and especially, that a true revolution was going to take place in the treatment of cardio-vascular diseases. Towards the end of the 1960s, this revolution triggered new advances in life expectancy in countries where it had reached or even exceeded 70 years (Caselli, 1996). However, the countries which reached the latter level were not all able to enter this new phase of the health transition. In the mid-1960s, life expectancy in countries of Eastern Europe and the USSR began on the contrary to stagnate or even decline, due to an increase in mortality from cardiovascular diseases and to the spread of man-made diseases (linked in particular to alcoholism and violence). The developing countries began their health transition process at a later stage, and by the early 1950s, their average life expectancies were much lower than those of developed 5 "Man-made diseases" are diseases linked to the side effects of modernization (alcoholism, smoking, car accidents, etc.)
3 countries. However, after World War II, most countries made huge progress and joined the general trend of convergence. Thus, from the 1950s to the 1990s, countries like Korea in Asia, Chile in Latin America, or Tunisia in Africa (to name but a few) nearly caught up with the countries of the North (see Figure 2A). 35 40 45 50 55 60 65 70 75 80 85 1935 1945 1955 1965 1975 1985 1995 Japan Russia France Life expectancy at birth Hungary United States Figure 1. Life expectancy trends since the 1930s: East-West convergence and divergence (Sources: United States: Bureau of the census 1975, 1985, 1992, US Census Bureau 1999, Japan: Institute of population problems 1993, Nanjo et al. 1985, Statistics Bureau 2001, Russia: Shkolnikov et al. 1994, France: Vallin and Mesl�� 2001, other countries: United Nations 2001.) However, once again this pattern suffers many exceptions. On one hand, though the struggle against infectious diseases, especially tropical diseases, was at first successful, some countries, mainly in Africa, were unable to reach a pace of progress sufficient to reduce the gap separating them from developed countries. During the 1980s and 1990s, this pace began to slacken and in some cases all progress even ceased. For instance, Figure 2B shows that Nigeria, which began at the same level as Tunisia in the 1950s, was far less successful than the latter today, life expectancy in Nigeria is 20 years shorter than in Tunisia. Worse still, and this is particularly true of Africa, the arrival of AIDS often caused severe reversals and towards the end of the 1980s, life expectancy levels suddenly dropped. This was the case in Zambia, which lost 11 years of life expectancy between 1980-1985 and 1995-2000, or in Zimbabwe, which lost almost 17 years of life expectancy during the same period (see Figure 2B). Today, Zambia���s life expectancy has dropped back to its level of the early 1950s, that is,
4 to 40 years, while Zimbabwe���s life expectancy has fallen far below its 1950 level (42.9 as compared to 47.7). 35 40 45 50 55 60 65 70 75 80 85 1950 1960 1970 1980 1990 2000 Japan France United States Chile Korea Tunisia A Life expectancy at birth 35 40 45 50 55 60 65 70 75 80 85 1950 1960 1970 1980 1990 2000 Chile Korea Tunisia Zimbabwe Zambia Nigeria B Life expectancy at birth Figure 2. Changes in life expectancy since the 1950s : North-South convergences (A) and South-South divergences (B) (Source: United Nations 2001) These disruptions strongly modify the overall pattern governing life expectancy trends until the 1970s. Figure 3A compares life expectancy gains between 1950-1955 and 1970-75 with the level reached by 1950-55. A glance to the figure clearly shows that at the lower levels (between 30 and 40 years), despite considerable variations, progress is usually rather limited (from 3 to 10 years in 20 years). The countries with a life expectancy of over 40 advanced more rapidly: those whose life expectancy was between 45 and 55 in 1950-55 gained from 9 to 15 years (and even more than 20 years in the case of China, an exceptional achievement). Last, in countries where life expectancy was rather high in the early 1950s, advances were much less spectacular: from 2 to 5 years in cases where life expectancy was over 65 in the early 1950s. Indeed, at first, in countries barely out of the "age of pestilence and famine", where life expectancy was still low, progress was slow, owing to the scope of the task and to the fact that the first advances benefited only a fraction of the population, mostly urban. At a later stage, as the health system reached its full capacity, simple and effective means to curb widespread endemic diseases were implemented throughout the country and life expectancy rapidly grew. However, as we move closer to life expectancy levels reached in developed countries, the pace slows down again, both because there is no longer much to be gained in the field of infectious diseases, and because subsequent progress relies on new findings in other domains (cardiovascular diseases, cancers, man-made diseases). In the past twenty years, however, this now well-known pattern (Vallin, 1968, 1989) has suffered several exceptions (Mesl�� and Vallin, 1997). Figure 3B is based on the same principle as Figure 3A, and covers the period from 1970-75 to 1995-2000. In this figure, the
5 picture is much less clear than in the previous one. Many countries still follow the previous pattern (even China), but there are numerous exceptions which concern very specific geopolitical areas. On one hand, many countries of tropical Africa are advancing at a much slower pace than other countries with similar life expectancy levels. Kenya, for example, with a life expectancy of over 50 years in 1970-75, gained less than Sierra Leone, whose life expectancy was only 35 in the early 70s. But above all, the AIDS epidemic triggered a decrease, and in some cases a sharp drop in the life expectancy levels of many African countries (about 10), among which Zambia, Zimbabwe, as mentioned earlier, as well as Botswana, Rwanda, Uganda, Namibia, etc. On the other hand, among the countries with the highest life expectancies in 1970-75, those of Eastern Europe (Central Europe and European republics of the former USSR) embarked on a period of stagnation and even decline, a shared phenomenon which clearly sets these countries apart from other industrialized countries. -15 -10 -5 0 5 10 15 20 25 25 35 45 55 65 75 Life expectancy in 1950-55 China Zimbabwe Botswana Zambia Russia Ukraine Belarus A Life expectancy gain between 1950-5 and 1970-5 -15 -10 -5 0 5 10 15 20 25 25 35 45 55 65 75 Life expectancy in 1970-75 Zimbabwe Uganda Botswana Zambia Rwanda Namibia Burundi Mozambique Russia Ukraine Belarus B Life expectancy gain between 1970-5 and 1995-2000 China Asia South America Industr. countries Eastern Europe Africa Figure 3. Relationship between initial level and life expectancy gains during two periods: A) from 1950-55 to 1970-75 B) from 1970-75 to 1995-2000 These developments have radically modified the distribution of the world population in terms of life expectancy. Figure 4 illustrates, at three different points in time (1950-55, 1970- 75 and 1995-2000), the cumulated populations of all the countries of the world, grouped per five-year sections of life expectancy at birth developed and developing countries are identified separately, according to the UN definition (Figures 4A, B and C). The dominating trend, from one period to the next, is the massive convergence of southern levels towards northern levels. In 1950-55, the life expectancies of most of the developing countries hovered somewhere between 35 and 45 years, far behind most developed countries, which for the most part neared a life expectancy of 65-70. In 1970-75, the wealthy countries still remained a close-knit group, adding another five years to their life expectancy, but the poor countries suddenly broke into separate groups, with a large portion of their populations nearly catching