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

Published March 11, 2024, in The Lancet (opens in a new window)

Abstract

Background

Estimates of demographic metrics are crucial to assess levels and trends of population health outcomes. The profound impact of the COVID-19 pandemic on populations worldwide has underscored the need for timely estimates in order to understand this unprecedented event within the context of long-term population health trends. 

The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) offers regularly updated and comparable estimates of health metrics. This study—part of the latest GBD release, GBD 2021—reports new demographic estimates for 1950–2021, with a particular emphasis on changes in mortality and life expectancy that occurred during the 2020–2021 COVID-19 pandemic period.

Methods

22 223 data sources from vital registration (VR), sample registration, surveys, censuses, and other sources were used for mortality estimation, with a subset of these sources used exclusively to estimate excess mortality due to the COVID-19 pandemic. 2026 data sources were used for population estimation. Additional sources were used to estimate migration; the effects of the HIV epidemic; and demographic discontinuities due to conflicts, famines, natural disasters, and pandemics, which are used as inputs for estimating mortality and population. 

Child mortality (under 5 years old) was estimated using spatiotemporal Gaussian process regression (ST-GPR), which synthesised 30 763 location-years of VR and sample registration data, 1365 surveys and censuses, and 80 other sources. ST-GPR was also used to estimate adult mortality (between 15 and 59 years old) based on information from 31 642 location-years of VR and sample registration data, 355 surveys and censuses, and 24 other sources. Estimates of child and adult mortality rates were then used to generate life tables with a relational model life table system. 

For countries with large HIV epidemics, life tables were adjusted using independent estimates of HIV-specific mortality generated via an epidemiological analysis of HIV prevalence surveys, antenatal clinic serosurveillance, and other data sources. 

Excess mortality due to the COVID-19 pandemic in 2020 and 2021 was determined by subtracting observed all-cause mortality (adjusted for late registration and mortality anomalies) from the mortality expected in the absence of the pandemic. Expected mortality was calculated based on historical trends using an ensemble of models. In location-years where all-cause mortality data were unavailable, we estimated excess mortality rates using a regression model with covariates pertaining to the pandemic. 

Population size was computed using a Bayesian hierarchical cohort component model. Life expectancy was calculated using age-specific mortality rates and standard demographic methods. For each measure, 95% uncertainty intervals (UIs) were calculated using the 25th and 975th ordered values from a 1000-draw posterior distribution. Estimates are reported for 204 countries and territories and 811 additional subnational locations for each year from 1950 through 2021.

Findings

Global all-cause mortality followed two distinct patterns over the study period: one of declining age-standardised mortality rates from 1950 through 2019 (a 62·8% [95% UI 60·5–65·1] decline), followed by one of increasing age-standardised mortality rates in the COVID-19 pandemic period of 2020–2021 (a 5·1% [0·9–9·6] increase). 

In contrast with the overall reverse in mortality trends during the pandemic period, child mortality continued to decline, with 4·66 million (3·98–5·50) global deaths under age 5 in 2021 compared to 5·21 million (4·50–6·01) in 2019. 

An estimated 131 million (126–137) people died globally from all causes in 2020 and 2021 combined, of which 15·9 million ( 14·7–17·2) died from the COVID-19 pandemic (measured by excess mortality, which includes deaths directly due to SARS-CoV-2 infection as well as those indirectly due to other social, economic, or behavioural changes associated with the pandemic). 

80 countries and territories experienced excess mortality rates exceeding 150 deaths per 100 000 population during at least one year of the pandemic, while 20 nations had a negative excess mortality rate in 2020 or 2021, meaning all-cause mortality in these countries was lower during the pandemic than expected based on historical trends. 

Between 1950 and 2021, global life expectancy at birth increased by 22·7 (20·8 –24·8) years, from 49·0 (46·7–51·3) to 71·7 (70·9–72·5) years. That said, global life expectancy at birth declined by 1·6 years (1·0–2·2) between 2019 and 2021, reversing historical trends. Only 32 of 204 countries and territories (15·7%) experienced an increase in life expectancy from 2019 to 2021. 

The global population reached 7·89 billion people in 2021, by which time 56 of 204 countries and territories had peaked and subsequently declined in population. The largest shares of population growth from 2020 to 2021 were in sub-Saharan Africa with 39·5% (28·4–52·7) and south Asia with 26·3% (9·0–44·7). 

From 2000 to 2021, the ratio of the population aged 65 years and older to the population aged less than 15 years increased in 188 of 204 nations (92·2%).

Interpretation

Global adult mortality rates dramatically increased during the COVID-19 pandemic in 2020 and 2021, reversing past decreasing trends, while child mortality rates continued to decline, albeit more slowly than in earlier years. 

Although COVID-19 had a substantial impact on many demographic indicators during the first two years of the pandemic, overall global health progress over the 72 years evaluated has been profound, with considerable improvements in mortality and life expectancy. 

Additionally, we observed a deceleration of global population growth in recent years, despite steady or increasing growth in lower income countries, combined with a continued global shift of population age structures towards older ages. 

These demographic changes will likely present future challenges to health systems, economies, and societies. The comprehensive demographic estimates reported here will enable researchers, policy makers, health practitioners, and other key stakeholders to better understand and address the profound changes that have occurred in the global health landscape following the first two years of the COVID-19 pandemic, as well as longer-term trends beyond the pandemic.

Funding

Bill & Melinda Gates Foundation.

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Citation

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. The Lancet. 11 March 2024. doi: 10.1016/S0140-6736(24)00476-8.

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