Elsevier

The Lancet

Volume 367, Issue 9524, 27 May–2 June 2006, Pages 1747-1757
The Lancet

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Global and regional burden of disease and risk factors, 2001: systematic analysis of population health data

https://doi.org/10.1016/S0140-6736(06)68770-9Get rights and content

Summary

Background

Our aim was to calculate the global burden of disease and risk factors for 2001, to examine regional trends from 1990 to 2001, and to provide a starting point for the analysis of the Disease Control Priorities Project (DCPP).

Methods

We calculated mortality, incidence, prevalence, and disability adjusted life years (DALYs) for 136 diseases and injuries, for seven income/geographic country groups. To assess trends, we re-estimated all-cause mortality for 1990 with the same methods as for 2001. We estimated mortality and disease burden attributable to 19 risk factors.

Findings

About 56 million people died in 2001. Of these, 10·6 million were children, 99% of whom lived in low-and-middle-income countries. More than half of child deaths in 2001 were attributable to acute respiratory infections, measles, diarrhoea, malaria, and HIV/AIDS. The ten leading diseases for global disease burden were perinatal conditions, lower respiratory infections, ischaemic heart disease, cerebrovascular disease, HIV/AIDS, diarrhoeal diseases, unipolar major depression, malaria, chronic obstructive pulmonary disease, and tuberculosis. There was a 20% reduction in global disease burden per head due to communicable, maternal, perinatal, and nutritional conditions between 1990 and 2001. Almost half the disease burden in low-and-middle-income countries is now from non-communicable diseases (disease burden per head in Sub-Saharan Africa and the low-and-middle-income countries of Europe and Central Asia increased between 1990 and 2001). Undernutrition remains the leading risk factor for health loss. An estimated 45% of global mortality and 36% of global disease burden are attributable to the joint hazardous effects of the 19 risk factors studied. Uncertainty in all-cause mortality estimates ranged from around 1% in high-income countries to 15–20% in Sub-Saharan Africa. Uncertainty was larger for mortality from specific diseases, and for incidence and prevalence of non-fatal outcomes.

Interpretation

Despite uncertainties about mortality and burden of disease estimates, our findings suggest that substantial gains in health have been achieved in most populations, countered by the HIV/AIDS epidemic in Sub-Saharan Africa and setbacks in adult mortality in countries of the former Soviet Union. Our results on major disease, injury, and risk factor causes of loss of health, together with information on the cost-effectiveness of interventions, can assist in accelerating progress towards better health and reducing the persistent differentials in health between poor and rich countries.

Introduction

An important input to decision-making and planning processes in health is a consistent and comparative description of the burden of diseases and injuries and their associated risk factors. Assessment of the comparative importance of risks to health and their outcomes in different populations depends on a framework for integrating, validating, analysing, and disseminating the fragmentary, and at times contradictory, information that is available on a population's health, along with some understanding of how that population's health is changing. The Global Burden of Disease (GBD) study quantified the health effects of more than 100 diseases and injuries and ten selected risk factors for the world as a whole and for eight regions in 1990.1, 2, 3 As well as generating comprehensive and internally consistent estimates of mortality and morbidity by age, sex, and region,4 the 1990 GBD study used a new metric—disability-adjusted life years (DALYs)—to quantify the burden of diseases, injuries, and risk factors with a single currency based on years of life lost due to premature mortality (YLL) and years of life lived in less than full health.5

Between 1998 and 2004, WHO invested in improving the conceptual, methodological, and empirical basis of assessments of burden of disease and of the disease and injury burden attributable to major risk factors.6, 7, 8, 9 The summaries of consecutive revisions and updates were published yearly in WHO's World Health Reports. National applications of the burden of disease framework10, 11, 12 have also led to new data sources. Here, we present the results of the GBD study for 2001.

In addition to including improved methods and new and more extensive data, we incorporated three features into the 2001 assessment of the global burden of disease. First, we estimated changes in cause-specific mortality and burden of disease, to assess progress and setbacks, overall and for specific diseases, since 1990. Second, we examined the uncertainty of mortality and burden-of-disease estimates due to data limitations, and their sensitivity to social value choices built into the DALY metric. Third, researchers used the estimates of disease burden as the starting point for a comprehensive analysis of intervention cost-effectiveness in the Disease Control Priorities Project (DCPP).13 A joint initiative of the Fogarty International Center (FIC) of the US National Institutes of Health, the World Bank, WHO, and the Bill & Melinda Gates Foundation, the DCPP aims to provide a comprehensive assessment of health-system development priorities in developing countries. Such an assessment depends on an understanding of the need for various health interventions—ie, comparative magnitude of the burden of disease and risk factors—as well as the effectiveness or cost-effectiveness of interventions. We chose 2001 as the base year for analysis for consistency with the DCPP cost-effectiveness analyses. Here, we provide an overview of our methods and results; further information on data sources, methods, and detailed results are provided in the two DCPP volumes.13, 14

Section snippets

Mortality and cause of death estimates

We developed life tables for 192 WHO member states from available death registration data, sample registration systems (India, China), and data on child and adult mortality from censuses and surveys, such as the Demographic and Health Surveys (DHS) and UNICEF's Multiple Indicator Cluster Surveys (MICS). We calculated age-specific and sex-specific death rates for countries with one of three standard approaches:7 routine life-table methods for countries with complete vital registration; standard

Results

Worldwide, slightly more than 56 million people died in 2001. One-third of these deaths were from communicable, maternal, and perinatal conditions and nutritional deficiencies (group I). This proportion has remained almost unchanged since 1990. Among these diseases, HIV/AIDS accounted for only 2% of deaths in 1990, but for 14% in 2001. Excluding HIV/AIDS, deaths due to group I conditions fell from one-third of total deaths in 1990 to less than one-fifth in 2001. 97% of the group I deaths not

Discussion

As programmes and policies to improve health worldwide become more widespread, so too will the need for more comprehensive, credible, and critical assessments to periodically monitor population health and the success, or otherwise, of these policies and programmes. The 1990 GBD study highlighted the importance of some conditions, particularly mental health disorders, and drew global public-health attention to the unrecognised burden of injuries. The results of the 2001 GBD study reinforce the

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