INTRODUCTION TO TRANSITIONS IN DISEASE BURDEN
A transition in disease burden, the general notion of a shift from communicable to noncommunicable causes of disease and injury, remains a powerful framework for global and regional health policy debates.1 In 1971, Omran outlined the concept of the epidemiological transition to describe the changing pattern of causes of death that results from sociodemographic development.2 The epidemiological transition is an extension of the conception of the demographic transition. In the demographic transition, a characteristic evolution occurs in populations over time toward reduced fertility rates, reduced mortality rates, and an older-age distribution of the population. The widely used concept of the epidemiological transition adds the idea that, in addition to these changes, a characteristic change occurs in the contributing causes of death.1 The epidemiological transition has been broadened to encompass a more general health transition, including both morbidity and mortality. The developments of modern healthcare and medicine drastically reduce infant mortality rates and extend average life expectancy. These factors, coupled with subsequent declines in fertility rates, have catalyzed a transition to noncommunicable diseases (NCDs) as increasingly important causes of health loss. The notion of the epidemiological transition has also been expanded to recognize a transition phase that may lead to a double burden of disease, the growing threat of NCDs as causes of health loss while infectious diseases remain highly prevalent. Too often, the health system may continue to rely heavily on the conventional infectious disease paradigm and be unresponsive to this emerging epidemiological shift.3
This chapter describes transitions in disease burden and their determinants, drawing from the Global Burden of Disease (GBD) study and other sources. Disease burden and epidemiological transition measurements should be sufficiently comprehensive to capture the causes of premature death and disability, as well as the major risk factors that underlie disease and injury.4 GBD is the largest and most comprehensive study to date to measure epidemiological levels and trends worldwide. It is a systematic, scientific effort that uses available data of multiple sources to quantify the comparative magnitude of health loss due to diseases, injuries, and risk factors by age, sex, and geographies for specific points in time. In light of the importance of understanding the concept of disease burden and related issues as a foundation for the material in the subsequent chapters and for all work in global health, we present a brief description of disease burden measurements, and a more detailed discussion of trends by region and disease within the three GBD disease categories of communicable, maternal, neonatal, and nutritional diseases; NCDs; and injuries. We also discuss the implications of these findings for global health programs and policies, and for achievement of the Sustainable Development Goals (SDGs), as well as for mechanisms to improve measurement of disease burden and the highest priorities for future research and training in global health.
MEASURING GLOBAL AND REGIONAL DISEASE BURDEN TRANSITIONS