Elsevier

The Lancet

Volume 380, Issue 9859, 15 December 2012–4 January 2013, Pages 2071-2094
The Lancet

Articles
Age-specific and sex-specific mortality in 187 countries, 1970–2010: a systematic analysis for the Global Burden of Disease Study 2010

https://doi.org/10.1016/S0140-6736(12)61719-XGet rights and content

Summary

Background

Estimation of the number and rate of deaths by age and sex is a key first stage for calculation of the burden of disease in order to constrain estimates of cause-specific mortality and to measure premature mortality in populations. We aimed to estimate life tables and annual numbers of deaths for 187 countries from 1970 to 2010.

Methods

We estimated trends in under-5 mortality rate (children aged 0–4 years) and probability of adult death (15–59 years) for each country with all available data. Death registration data were available for more than 100 countries and we corrected for undercount with improved death distribution methods. We applied refined methods to survey data on sibling survival that correct for survivor, zero-sibling, and recall bias. We separately estimated mortality from natural disasters and wars. We generated final estimates of under-5 mortality and adult mortality from the data with Gaussian process regression. We used these results as input parameters in a relational model life table system. We developed a model to extrapolate mortality to 110 years of age. All death rates and numbers have been estimated with 95% uncertainty intervals (95% UIs).

Findings

From 1970 to 2010, global male life expectancy at birth increased from 56·4 years (95% UI 55·5–57·2) to 67·5 years (66·9–68·1) and global female life expectancy at birth increased from 61·2 years (60·2–62·0) to 73·3 years (72·8–73·8). Life expectancy at birth rose by 3–4 years every decade from 1970, apart from during the 1990s (increase in male life expectancy of 1·4 years and in female life expectancy of 1·6 years). Substantial reductions in mortality occurred in eastern and southern sub-Saharan Africa since 2004, coinciding with increased coverage of antiretroviral therapy and preventive measures against malaria. Sex-specific changes in life expectancy from 1970 to 2010 ranged from gains of 23–29 years in the Maldives and Bhutan to declines of 1–7 years in Belarus, Lesotho, Ukraine, and Zimbabwe. Globally, 52·8 million (95% UI 51·6–54·1 million) deaths occurred in 2010, which is about 13·5% more than occurred in 1990 (46·5 million [45·7–47·4 million]), and 21·9% more than occurred in 1970 (43·3 million [42·2–44·6 million]). Proportionally more deaths in 2010 occurred at age 70 years and older (42·8% in 2010 vs 33·1% in 1990), and 22·9% occurred at 80 years or older. Deaths in children younger than 5 years declined by almost 60% since 1970 (16·4 million [16·1–16·7 million] in 1970 vs 6·8 million [6·6–7·1 million] in 2010), especially at ages 1–59 months (10·8 million [10·4–11·1 million] in 1970 vs 4·0 million [3·8–4·2 million] in 2010). In all regions, including those most affected by HIV/AIDS, we noted increases in mean ages at death.

Interpretation

Despite global and regional health crises, global life expectancy has increased continuously and substantially in the past 40 years. Yet substantial heterogeneity exists across age groups, among countries, and over different decades. 179 of 187 countries have had increases in life expectancy after the slowdown in progress in the 1990s. Efforts should be directed to reduce mortality in low-income and middle-income countries. Potential underestimation of achievement of the Millennium Development Goal 4 might result from limitations of demographic data on child mortality for the most recent time period. Improvement of civil registration system worldwide is crucial for better tracking of global mortality.

Funding

Bill & Melinda Gates Foundation.

Introduction

Accurate estimation of the number of deaths in each age and sex group in a country, region, or worldwide is a crucial starting point for assessment of the global burden of disease. Information about rates of mortality at different ages, especially what might reasonably be regarded as premature mortality, is an important impetus for public policy action, especially when the causes of premature mortality can be reliably established. Years of life lost (YLLs) due to premature mortality made up nearly two-thirds of the global burden of disease in 2010.1 Levels of mortality have been changing strikingly in the past 40 years and substantial progress has been made in reduction of the number of deaths in children younger than 5 years, postponing deaths to progressively older ages.2, 3 However, the number of young adult deaths has increased in the past 20 years, especially in eastern Europe because of epidemics of mortality related to alcohol overconsumption and in eastern and southern sub-Saharan Africa because of HIV/AIDS.1, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 A careful assessment of the demographic evidence on the levels of age-specific mortality is an integral component of any Global Burden of Disease Study: such analyses require the sum of deaths from specific causes to equal the independently assessed level of mortality from all causes, for every age and sex group. Such assessment is not a straightforward addition of reported causes. Because there are likely to be many more data reported for levels of all-cause mortality than there are for individual causes, the independent assessment of age-specific mortality is crucial to constrain the often less robust estimates of cause-specific mortality within each population group defined by age and sex.

Accurate measurement of age-specific mortality, however, is severely constrained by the fact that most developing countries have incomplete or no vital registration systems. Estimation of mortality rates requires application of a suite of demographic estimation methods that have been developed and refined during the past 60 years. For the Global Burden of Disease 2000 analysis,16 assessment of age-specific mortality was improved in two important ways compared with the Global Burden of Disease 1990 analysis.17 First, estimates for 2000 of under-5 mortality, measured as the probability of death between 0 years and 5 years of age (5q0), and mortality as a young adult or middle-aged adult, measured as the probability of death between 15 years and 60 years of age (45q15), were developed after review of available vital registration, sample registration, and census data and the application of the synthetic extinct generations and growth balance methods to correct for under-registration of deaths.18, 19, 20, 21, 22, 23 When no vital registration, census, or sample registration data were available, adult mortality was predicted on the basis of the rate of under-5 mortality. Second, a model life table system was developed by Murray and colleagues to generate age-specific death rates from estimates of under-5 mortality and 45q15.24 This analysis yielded life tables for 191 countries in 2000.25 Age-specific death rates from HIV/AIDS were separately estimated and added to the model-based estimates from this second stage, allowing for competing risks. The Global Burden of Disease 2000 mortality methods have continued to be applied by the WHO in their annual updates of mortality published in successive World Health Reports of 5q0 and 45q15.26, 27 An increasing body of evidence suggests a substantial divergence in the key determinants of trends in under-5 mortality and adult mortality;28, 29, 30, 31, 32, 33 therefore, the continued reliance on information about child mortality to predict adult mortality in a large number of countries is inadvisable.

The United Nations Population Division (UNPD) has generated demographic estimates since 1951 and produces biennial assessments of population, mortality, and fertility for every country from 1950 to 2050.34 Compared with WHO, the UNPD uses a broader array of data sources such as survey or census data for orphanhood, widowhood, and sibling survival data in selected countries. Another advantage of the UNPD estimates is that they assess a full time series of mortality and other demographic parameters for every country in each 2 year cycle of revision, compared with WHO analyses that look at serial cross-sectional data for mortality. The UNPD estimation strategy places great emphasis on the demographic balance equation, in which population in an age group must equal new entrants to the age group minus deaths plus net migration (the addition of immigration, minus emigration) and exits due to ageing out of a given age group. UNPD mortality estimates are, in effect, a byproduct of the primary task of estimating population by age and sex.34 Despite these advantages, the UNPD and WHO approaches have limitations. For example, neither approach produces uncertainty intervals (UIs) for their estimates of age-specific mortality, despite the very substantial uncertainty in the underlying data used to produce them and uncertainty from model specification. Moreover in countries with large HIV epidemics, both approaches assume that the Joint United Nations Programme on HIV/AIDS (UNAIDS) estimates of deaths due to HIV are additive to hypothetical HIV-free life tables. As a result, demographic sources such as vital registration, censuses, or surveys are not used to validate estimates of age-specific death rates in countries with moderate-to-large HIV epidemics.

As a key first step in the Global Burden of Diseases, Injuries, and Risk Factors Study 2010 (hereafter referred to as Global Burden of Disease Study 2010), we reassessed levels and trends of age-specific mortality worldwide. Improved methods for estimation of completeness of vital registration,35 analysis of sibling history data,36 and synthesis of data with UIs3, 4, 37 provide the basis for robust estimation of age-specific death rates. We used these advances, and a further extension of the Brass relational model life tables, to develop a time series of annual age-specific mortality rates for 187 countries from 1970 to 2010, including uncertainty. In this report and accompanying appendix, we present the data, methods, and key findings of the Global Burden of Disease Study 2010 on levels, trends, and age patterns of mortality worldwide.

Section snippets

Overview

Because vital registration systems in most developing countries are incomplete, measurement of child and adult mortality requires use of multiple sources of data and the application of appropriate methods. Our approach to mortality estimation can be divided into three components: estimation of under-5 mortality, estimation of adult mortality, and estimation of age-specific mortality. Figure 1 provides a high-level summary of the mortality estimation process, including different data sources and

Results

Table 1 shows how global life expectancy changed in the past 40 years. From 1970 to 2010, male life expectancy at birth increased by 11·1 years and female life expectancy at birth increased by 12·1 years. The greater increase in female life expectancy widened the gap between the sexes from 4·8 years in 1970 to 5·7 years in 2010. Global life expectancy increased about 3–4 years per decade for both sexes in every decade apart from the 1990s, when smaller improvements were recorded (1·4 years for

Discussion

Global life expectancy has increased substantially in the past 40 years for men and women, despite major global and regional health crises. This increase has been driven by large declines (≥60%) in child mortality, declines of 40% or more in adult female mortality, and declines of 15–35% for adult male mortality, dependent on age group. Global population growth from 3·7 billion in 1970 to 6·9 billion in 2010,34 combined with a rise in the average age of the population, has led to an increase in

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