Chapter 1: Global Health: today's challenges
The global picture
Life expectancy improves -- but not for all
Over the past 50 years, average life expectancy at birth has increased globally by almost 20 years, from 46.5 years in 1950--1955 to 65.2 years in 2002. This represents a global average increase in life expectancy of 4 months per year across this period. On average, the gain in life expectancy was 9 years in developed countries (including Australia, European countries, Japan, New Zealand and North America), 17 years in the high-mortality developing countries (with high child and adult mortality levels), including most African countries and poorer countries in Asia, the Eastern Mediterranean Region and Latin America; and 26 years in the low-mortality developing countries. As shown in Figure 1.1, the large life expectancy gap between the developed and developing countries in the 1950s has changed to a large gap between the high-mortality developing countries and others.
Life expectancy at birth in 2002 ranged from 78 years for women in developed countries to less than 46 years for men in sub-Saharan Africa, a 1.7-fold difference in total life expectancy. Exceptions to the life expectancy increases in most regions of the world in the last 50 years are Africa and countries of eastern Europe formerly in the Soviet Union. In the latter case, male and female life expectancies at birth declined, by 2.9 years and 1 year, respectively, over the period 1990 to 2000. Estimated life expectancies for males and females for 2002 are given in Annex Table 1 for all Member States of the World Health Organization (WHO).
The increases in life expectancy that occurred in the first half of the 20th century in developed countries were the result of rapid declines in mortality, particularly infant and maternal mortality, and that caused by infectious diseases in childhood and early adulthood. Access to better housing, sanitation and education, a trend to smaller families, growing incomes, and public health measures such as immunization against infectious diseases all contributed greatly to this epidemiological transition. In many developed countries, this shift started approximately 100 to 150 years ago. In a number of countries, such as Japan, the transition started later but proceeded much more quickly. In many developing countries, the transition started even later and has not yet been completed. In developed countries, improvements in life expectancy now come mainly from reductions in death rates among adults.
Global mortality patterns
Almost 57 million people died in 2002, 10.5 million (or nearly 20%) of whom were children of less than 5 years of age (see Figure 1.2). Of these child deaths, 98% occurred in developing countries. Over 60% of deaths in developed countries occur beyond age 70, compared with about 30% in developing countries. A key point is the comparatively high number of deaths in developing countries at younger adult ages (15--59 years). Just over 30% of all deaths in developing countries occur at these ages, compared with 20% in richer regions. This vast premature adult mortality in developing countries is a major public health concern.
Developing countries themselves are a very heterogeneous group in terms of mortality (Figure 1.1). A contrast between low-mortality developing countries such as China (with more than one-sixth of the world's population) and high-mortality countries in Africa (with one-tenth of the global population) illustrates the extreme diversity in health conditions among developing countries. Less than 10% of deaths in China occur below 5 years of age compared with 40% in Africa. Conversely, 48% of deaths in China occur beyond age 70, compared with only 10% in Africa.1
Although risk of death is the simplest comparable measure of health status for populations, there has been increasing interest in describing, measuring and comparing health states of populations. Mortality statistics, in particular, substantially underestimate the burden from noncommunicable adult disease because they exclude non-fatal health outcomes such as depression and visual impairment. A useful method of formulating a composite summary of disease burden is to calculate disability-adjusted life years (DALYs), which combine years of life lost (YLLs) through premature death with years lived with disability (YLDs) (1). One DALY can be thought of as one lost year of "healthy" life and the measured disease burden is the gap between a population's health status and that of a normative global reference population with high life expectancy lived in full health. In terms of DALYs, 36% of total lost years of healthy life for the world in 2002 were a result of disease and injury in children aged less than 15 years, and almost 50% as a result of disease and injury in adults aged 15--59 years (see Figure 1.3).2
As Figure 1.3 illustrates, child survival continues to be a major focus of the international health agenda for developing countries (2). Because nearly 90% of global deaths under age 15 occur before the age of 5, the following sections focus on child deaths under 5 years. In contrast, the international effort to understand the magnitude of challenges to adult health in developing countries is still in its early stages. Even at present, there remains a perception that adult health is of great concern only in wealthy countries, where premature mortality among children has been substantially reduced. However, Figures 1.2 and 1.3 also illustrate the high proportion of burden of disease and injury suffered by adults in developing countries, a growing burden that requires urgent action by the global public health community. This chapter therefore first examines trends and issues in child health, focusing on ages 0--4, then among adults aged 15--59 years and among adults aged 60 years and over.
Unfortunately, complete cause-specific death registration data are routinely available for only a minority of the world's countries (see Chapter 7 and the Explanatory Notes in the Statistical Annex). However, complete or incomplete vital registration data (see Box 1.1) together with sample registration systems now capture one-third of deaths globally and provide information on 74% of global mortality, and these have been used to analyse adult mortality patterns and trends here.
Box 1.1 Sentinel vital registration in the United Republic of Tanzania
Accurate statistics on basic demographic events are an important foundation of rational health and public policy. Unfortunately, reliable vital registration is lacking for the vast majority of the world's poorest countries. Some new approaches to meeting the need for mortality and morbidity data have been pioneered in the United Republic of Tanzania. In 1992, the Ministry of Health established the Adult Morbidity and Mortality Project (AMMP) in partnership with the University of Newcastle upon Tyne, England, and with funding from the United Kingdom Department for International Development.
AMMP developed a demographic surveillance system and verbal autopsy tools for measuring levels and causes of death, and a validated tool for estimating household consumption expenditure to monitor income poverty. One of the initial project aims was to establish baseline levels of adult mortality by cause in three selected districts (3,5). In 1997, the Ministry of Health elected to expand data collection to a larger sample of districts and to establish a national sentinel system for health and poverty monitoring. In addition, the contributions of other demographic surveillance sites were coordinated to produce annual health statistics abstracts and public health sector performance profiles.
In 2002, sentinel vital registration, cause of death, and poverty monitoring figures flowing from five sites managed by the Ministry of Health and local councils and three sites managed by health development and research bodies began to provide essential indicators to the National Poverty Monitoring Master Plan. In the context of all information systems in the United Republic of Tanzania that produce demographic, health and poverty indicators, sentinel demographic surveillance generates a large number of indicators from a sample of over 500 000 people, at a per capita recurrent cost of US$ 0.02 per year. These costs are considerably less than for many other systems.
At the local level, AMMP has helped districts to feed sentinel surveillance information about the prevailing burden of disease back to community members who have, in turn, actively participated in setting priorities for district health. One local council was prompted by data on health-seeking for children dying at home from acute febrile illness to increase the resources allocated to fight malaria and to promote the use of treated bednets. At the national level, these same data provided an evidence base for a policy change in first-line malaria drug use, and the overall cause-specific mortality burden measured in years of life lost was a key input to the design of the first national package of essential health interventions. Drawing on the poverty data from sentinel sites, it has also been possible to provide government with solid evidence about how health intervention priorities among the poorest citizens differ from those of others.