The 20th Century Takeoff in Human Health
The 20th century differed markedly from previous history in two critical domains:
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First, the rapid economic growth that had begun in the 19th century in countries of the North Atlantic diffused widely around the globe while continuing in the countries where it originated (DeLong 2000; Maddison 1999).
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Second, human mortality rates plummeted, and other dimensions of health improved dramatically. These changes also began in the North Atlantic countries in the 19th century but remained modest until the 20th century, during which the rate of improvement increased and spread to most of the rest of the world (Easterlin 1996, 1999; Oeppen and Vaupel 2002).
Improvements in Health
This section briefly documents the magnitude of health improvements and then points to the challenges that remain. For the past 160 years, life expectancy in the healthiest countries has increased steadily. At the same time, differences in life expectancy between those countries and much of the rest of the world have narrowed. Figure 1.1 depicts trends in female life expectancy in the country with the highest estimated level of life expectancy. From about 1600 to about 1840, there is fluctuation but no clear trend; after 1840, the graph turns upward at a surprisingly uniform rate of improvement: maximum life expectancy increased by about two and one-half years per decade for 160 years.
[Figure
1.1]
Table 1.1 shows progress in life expectancy by World Bank region between 1960 and 2002. (Map 1 on the inside front cover depicts the World Bank regions.) For the first three decades of this period, progress was remarkably fast—a gain of 6.3 years in life expectancy per decade on average, albeit with substantial regional variation. Progress continued between 1990 and 2002 in the low- and middle-income countries but at a much slower pace. This slower pace is due, in great part, to mortality increases from HIV/AIDS. Sub-Saharan Africa actually lost more than four years of life expectancy.
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Since 1950, life expectancy in the median country has steadily converged toward the maximum and cross-country differences have decreased markedly. This reduction in inequality in health contrasts with long-term increases in income inequality between and within countries. Despite the magnitude of global improvements, many countries and populations have failed to share in the overall gains or have even fallen behind. Some countries—for example, Sierra Leone—remain far behind (figure 1.1). China's interior provinces lag behind the more advantaged coastal regions. Indigenous people everywhere probably lead far less healthy lives than do others in their respective countries, although confirmatory data are scant.
Reasons for remaining health inequalities lie only partially in income inequality: the experiences of China, Costa Rica, Cuba, Sri Lanka, and Kerala state in India, among many others, conclusively show that dramatic improvements in health can occur without high or rapidly growing incomes. The experiences of countries in Europe in the late 19th and early 20th centuries similarly show that health conditions can improve without prior or concomitant increases in income (Easterlin 1996). A recent review, undertaken in part as background for this volume, identified many specific examples of low-cost interventions leading to large and carefully documented health improvements (Levine and others 2004). The public sector initiated and financed virtually all of these interventions. The goal of this book is to assist decision makers—particularly those in the public sector—to realize the potential for low-cost intervention to rapidly improve the health and welfare of their populations.
Remaining Challenges
Four central challenges for health policy ensue from the pace and unevenness of the progress just documented and from the evolving nature of microbial threats to human health.
Epidemiological Transition
First, the next two decades will see continuation of trends resulting from the dramatic mortality declines of recent decades. The key phenomenon is that the major noncommunicable diseases—circulatory system diseases, cancers, and major psychiatric disorders—are fast replacing (or adding to) the traditional scourges—particularly infectious diseases and undernutrition in children. This phenomenon results in substantial part from rapid relative population growth at the older ages, when noncommunicable diseases become manifest. Additionally, injuries resulting from road traffic are replacing more traditional forms of injury. Using data from Chile, figure 1.2 illustrates the huge increase in the relative importance of injuries, cancers, and cardiovascular disease between 1909 and 1999. Responding to this epidemiological transition with sharply constrained resources is a key challenge. Tables 1.A1 and 1.A2 (see annex 1.A) provide cause-specific summaries of death and disease burden, measured in DALYs, in 2001 for the world as a whole and for low- and middle-income countries as a group as well as for high-income countries. Those summaries indicate that noncommunicable disease already accounts for over half of all deaths in the low-and middle-income countries, although nearly 40 percent of deaths continue to be from infection, undernutrition, and maternal conditions, creating a "dual burden" that Julio Frenk and colleagues have pointed to (Bobadilla and others 1993).
[Figure
1.2]
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HIV/AIDS Epidemic
A second key challenge is the HIV/AIDS epidemic. Control efforts and successes have been very real but, with only a few exceptions, limited to upper-middle-income and high-income countries. Poorer countries remain in the epidemic's deadly path.
New Pandemics
The global influenza pandemic of 1918 resulted in more than 40 million human deaths, exceeding the 20th-century toll of HIV/AIDS or of World Wars I and II. Continued evolution of the influenza virus leaves the world at risk of another such pandemic—as has been much discussed in the press as this book goes to print. If the H5N1 strain of avian influenza, for example, evolved so that (like the human flu) it could be efficiently transmitted from human to human, a major pandemic would be likely. Preparing for such an eventuality is the third great challenge to global health.
Unequal Progress
A fourth key challenge results from continued high levels of inequality in health conditions across and within countries. Bourguignon and Morrisson (2002) have stressed that global inequalities are declining if one properly accounts for convergence across countries in health conditions, which more than compensates for income divergence. However, in far too many countries health conditions remain unacceptably—and unnecessarily—poor. This factor is a source of grief and misery, and it is a sharp brake on economic growth and poverty reduction. From 1990 to 2001, for example, the under-five mortality rate remained stagnant or increased in 23 countries. In another 53 countries (including China), the rate of decline in under-five mortality in this period was less than half of the 4.3 percent per year required to reach the fourth Millennium Development Goal (MDG-4) (see map 2 on the inside back cover of this book). Meeting the MDG for under-five mortality reduction by 2015 is not remotely possible for these countries. Yet the examples of many other countries, often quite poor, show that with the right policies dramatic reductions in mortality are possible. A major goal of this volume is to identify strategies for implementing interventions that are known to be highly cost-effective for dealing with the health problems of countries remaining behind—for example, treatment for diarrhea, pneumonia, TB, and malaria; immunization; and other preventive measures against a large proportion of those diseases.
