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.
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.
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.
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.