Life expectancy and age-specific mortality are key demographic indicators to monitor global health and identify emerging trends. The COVID-19 pandemic highlighted the critical need for timely estimates of all-cause mortality to guide effective public health responses and policymaking. Traditional demographic tools often face limitations in data availability and analytical speed, specifically during crises. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) is a comprehensive international initiative that updates estimates of health metrics across time, sex, age, cause, and location. The 2023 GBD release expands this framework by employing advanced statistical modeling to generate updated global mortality and life expectancy estimates from 1950 to 2023.
This study aimed to deliver comparable, comprehensive, and timely estimates of all-cause mortality and life expectancy over more than 7 decades. By leveraging advanced statistical methods and newly available data sources, the analysis accounted for dynamic demographic trends driven by population growth, aging, and the COVID-19 pandemic. Differences in mortality patterns by sex, region, and age were identified to inform future health planning and policy development.
Data from 24,025 sources, including national surveys, censuses, sample registration, vital registration systems, and other demographic records, were analyzed in this study. This study covered 204 countries and territories and 660 subnational areas in 20 countries between 1950 and 2023. Mortality estimates were generated for both sexes across 25 age groups. For children aged 5-14 years, full birth history information was used, while surveillance systems and sibling histories informed estimates for individuals aged 15-49 years.
A unified modeling framework, OneMod, was developed to integrate parametric and non-parametric methods. This model involved two key stages: a regression analysis using generalized linear models to account for age-specific variables such as the Socio-demographic Index (SDI) and population attributable fractions (PAF) for all combined risk factors, followed by non-parametric multivariate kernel regression to smooth residuals across age and time, capturing demographic trends without overfitting. Uncertainty intervals were calibrated using Pearson residuals to generate 95% uncertainty intervals from 1,000 model draws. Standard demographic methods were applied to calculate life expectancy from age-specific mortality rates.
In 2023, an estimated 60.1 million deaths occurred globally, including 4.67 million deaths in children under five years. While population growth and aging contributed to a 35% rise in total annual deaths since 1950, the global age-standardized mortality rate decreased by approximately 66.6% over the same period. From 2011 to 2023, mortality trends varied widely across regions and age groups. East Asia experienced the most substantial decline in under-five mortality (67.7%). High-income North America saw notable increases among individuals aged 5 to 39 years. Adolescent and young adult mortality rose in Eastern Europe with increases of over 50% in some groups.
Sub-Saharan Africa showed mixed outcomes: mortality among children aged 5–14 years and young women aged 15–29 years exceeded previous GBD estimates, whereas mortality in those aged 50 and above remained low. Global life expectancy steadily increased from 1950 to 2019, rising from 51.2 to 76.3 years in females and from 47.9 to 71.4 years in males. Life expectancy temporarily declined during the COVID-19 pandemic in 2021 but rebounded by 2023 to near pre-pandemic levels. By 2023, over 95% of countries had partially recovered, and nearly two-thirds had mortality rates equal to or lower than 2019 levels.
This study provides new insights, such as high mortality among adolescents and young adult women and low mortality among the elderly in sub-Saharan Africa, highlighting persistent regional disparities in mortality patterns before, during, and after the COVID-19 pandemic. These findings offer critical evidence for policymakers, enabling targeted interventions for high-risk populations and better preparedness for future global health challenges.
Reference: GBD 2021 Demographics Collaborators. Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950-2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021. Lancet. 2024;403(10440):1989-2056. doi:10.1016/S0140-6736(24)00476-8
