Epidemiological and demographic trends and projections in global health from 1970 to 2050: a descriptive analysis from the third Lancet Commission on Investing in Health, Global Health 2050

BACKGROUND: Systematic analyses of global health trends can provide an accurate narrative of progress and challenges. We analysed the impact of changing age-specific mortality (epidemiology) and age structure (demography) on crude death rates (CDRs) and causes of death with large or rising mortality to inform the third Lancet Commission on Investing in Health. METHODS: Data from the World Population Prospects 2024 and Global Health Estimates 2021 were used to assess epidemiological and demographic trends, including CDR (defined as the total number of deaths divided by the total mid-year population, reported per 1000 population), all-cause age-specific mortality rates for 1970-2050, and selected cause-specific mortality rates from 2000-19. We excluded data for 2020-23 to avoid effects of the COVID-19 pandemic. For estimating decadal changes in cause-specific mortality rates, we combined the estimates into the following age groups: 0-14, 15-49, 50-69, and 70 years and older. FINDINGS: Mortality rates declined substantially across age groups in most regions, with rapid improvements observed in recent decades. Between the 2000s (ie, 2000-10) and 2010s (ie, 2010-19), the mortality decline accelerated in China, central and eastern Europe, India, and Latin America and the Caribbean in ages 0-14 years and 15-49 years, but decelerated in the north Atlantic, the USA, and western Pacific and southeast Asia. For ages 50-69 years, mortality decline decelerated in all regions except sub-Saharan Africa. The USA experienced not only deceleration but increase in mortality rates in those aged 15-49 years and 50-69 years. Globally, the lowest CDR was reported in 2019. In the past, CDR has declined primarily because of decreasing age-specific mortality rates. Future trends suggest that changing population age structure will drive a large increase in CDR. Age-specific mortality rates from major diseases declined once population changes were accounted for. The exception was diabetes, with accelerating increase in age-specific death rates in all regions, with especially high rates in central and eastern Europe and India. INTERPRETATION: There is reason for optimism regarding global health progress, but disparities and emerging challenges persist. Falling age-specific mortality rates show progress; however, rapid ageing brings new challenges. Slowing mortality declines in some regions require enhanced efforts. Rising mortality among middle-aged Americans emphasises that continuous improvements require concerted efforts. Key recommendations include prioritising interventions to address specific health challenges and adapting health-care systems to demographic transitions. FUNDING: The Norwegian Agency for Development Cooperation and the Bill & Melinda Gates Foundation.