Background: Plausible projections of future mortality and disability are a useful aid in decisions on priorities for health research, capital investment, and training. Rates and patterns of ill health are determined by factors such as socioeconomic development, educational attainment, technological developments, and their dispersion among populations, as well as exposure to hazards such as tobacco. As part of the Global Burden of Disease Study (GBD), we developed three scenarios of future mortality and disability for different age-sex groups, causes, and regions.
Methods: We used the most important disease and injury trends since 1950 in nine cause-of-death clusters. Regression equations for mortality rates for each cluster by region were developed from gross domestic product per person (in international dollars), average number of years of education, time (in years, as a surrogate for technological change), and smoking intensity, which shows the cumulative effects based on data for 47 countries in 1950-90. Optimistic, pessimistic, and baseline projections of the independent variables were made. We related mortality from detailed causes to mortality from a cause cluster to project more detailed causes. Based on projected numbers of deaths by cause, years of life lived with disability (YLDs) were projected from different relation models of YLDs to years of life lost (YLLs). Population projections were prepared from World Bank projections of fertility and the projected mortality rates.
Findings: Life expectancy at birth for women was projected to increase in all three scenarios; in established market economies to about 90 years by 2020. Far smaller gains in male life expectancy were projected than in females; in formerly socialist economies of Europe, male life expectancy may not increase at all. Worldwide mortality from communicable maternal, perinatal, and nutritional disorders was expected to decline in the baseline scenario from 17.2 million deaths in 1990 to 10.3 million in 2020. We projected that non-communicable disease mortality will increase from 28.1 million deaths in 1990 to 49.7 million in 2020. Deaths from injury may increase from 5.1 million to 8.4 million. Leading causes of disability-adjusted life years (DALYs) predicted by the baseline model were (in descending order): ischaemic heart disease, unipolar major depression, road-traffic accidents, cerebrovascular disease, chronic obstructive pulmonary disease, lower respiratory infections, tuberculosis, war injuries, diarrhoeal diseases, and HIV. Tobacco-attributable mortality is projected to increase from 3.0 million deaths in 1990 to 8.4 million deaths in 2020.
Interpretation: Health trends in the next 25 years will be determined mainly by the ageing of the world's population, the decline in age-specific mortality rates from communicable, maternal, perinatal, and nutritional disorders, the spread of HIV, and the increase in tobacco-related mortality and disability. Projections, by their nature, are highly uncertain, but we found some robust results with implications for health policy.
PIP: As part of the Global Burden of Disease Study, three scenarios of future mortality and disability were identified. The scenarios were based on future health status as a function of projected changes in key socioeconomic variables that influence health status. Regression equations for mortality rates for nine cause-of-death clusters were developed by region based on gross domestic product per person, average number of years of education, time (as a proxy for technological change), and smoking intensity. Life expectancy at birth was projected, in all three scenarios, to increase for women (to about 90 years in established market economies by 2020), with far smaller gains in male life expectancy. Worldwide, annual mortality from communicable maternal, perinatal, and nutritional disorders (group 1 causes) is expected to decline from 17.2 million to 10.3 million in 2020 in the baseline model. Also expected is a very large increase in deaths from non-communicable diseases (group 2 causes) from 28.1 million in 1990 to 49.7 million in 2020. Deaths from injuries (group 3) are projected to increase from 5.1 million to 8.4 million. Diarrheal diseases, perinatal disorders, measles, and malaria are expected to decline dramatically as causes of death in the 1990-2020 period, while lung cancer, stomach cancer, war injuries, liver cancer, and HIV are expected to move up five or more places in the ranking. In 2020, the 10 leading causes of disability-adjusted life-years (in descending order) are projected to be ischemic heart disease, unipolar major depression, road traffic accidents, cerebrovascular disease, chronic obstructive pulmonary disease, lower respiratory infections, tuberculosis, war injuries, diarrheal diseases, and HIV. Tobacco-attributable mortality is projected to increase from 3.0 million in 1990 to 8.4 million in 2020 (9% of the worldwide mortality burden).