Elsevier

The Lancet

Volume 386, Issue 10010, 5–11 December 2015, Pages 2287-2323
The Lancet

Articles
Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013

https://doi.org/10.1016/S0140-6736(15)00128-2Get rights and content

Summary

Background

The Global Burden of Disease, Injuries, and Risk Factor study 2013 (GBD 2013) is the first of a series of annual updates of the GBD. Risk factor quantification, particularly of modifiable risk factors, can help to identify emerging threats to population health and opportunities for prevention. The GBD 2013 provides a timely opportunity to update the comparative risk assessment with new data for exposure, relative risks, and evidence on the appropriate counterfactual risk distribution.

Methods

Attributable deaths, years of life lost, years lived with disability, and disability-adjusted life-years (DALYs) have been estimated for 79 risks or clusters of risks using the GBD 2010 methods. Risk–outcome pairs meeting explicit evidence criteria were assessed for 188 countries for the period 1990–2013 by age and sex using three inputs: risk exposure, relative risks, and the theoretical minimum risk exposure level (TMREL). Risks are organised into a hierarchy with blocks of behavioural, environmental and occupational, and metabolic risks at the first level of the hierarchy. The next level in the hierarchy includes nine clusters of related risks and two individual risks, with more detail provided at levels 3 and 4 of the hierarchy. Compared with GBD 2010, six new risk factors have been added: handwashing practices, occupational exposure to trichloroethylene, childhood wasting, childhood stunting, unsafe sex, and low glomerular filtration rate. For most risks, data for exposure were synthesised with a Bayesian meta-regression method, DisMod-MR 2.0, or spatial-temporal Gaussian process regression. Relative risks were based on meta-regressions of published cohort and intervention studies. Attributable burden for clusters of risks and all risks combined took into account evidence on the mediation of some risks such as high body-mass index (BMI) through other risks such as high systolic blood pressure and high cholesterol.

Findings

All risks combined account for 57·2% (95% uncertainty interval [UI] 55·8–58·5) of deaths and 41·6% (40·1–43·0) of DALYs. Risks quantified account for 87·9% (86·5–89·3) of cardiovascular disease DALYs, ranging to a low of 0% for neonatal disorders and neglected tropical diseases and malaria. In terms of global DALYs in 2013, six risks or clusters of risks each caused more than 5% of DALYs: dietary risks accounting for 11·3 million deaths and 241·4 million DALYs, high systolic blood pressure for 10·4 million deaths and 208·1 million DALYs, child and maternal malnutrition for 1·7 million deaths and 176·9 million DALYs, tobacco smoke for 6·1 million deaths and 143·5 million DALYs, air pollution for 5·5 million deaths and 141·5 million DALYs, and high BMI for 4·4 million deaths and 134·0 million DALYs. Risk factor patterns vary across regions and countries and with time. In sub-Saharan Africa, the leading risk factors are child and maternal malnutrition, unsafe sex, and unsafe water, sanitation, and handwashing. In women, in nearly all countries in the Americas, north Africa, and the Middle East, and in many other high-income countries, high BMI is the leading risk factor, with high systolic blood pressure as the leading risk in most of Central and Eastern Europe and south and east Asia. For men, high systolic blood pressure or tobacco use are the leading risks in nearly all high-income countries, in north Africa and the Middle East, Europe, and Asia. For men and women, unsafe sex is the leading risk in a corridor from Kenya to South Africa.

Interpretation

Behavioural, environmental and occupational, and metabolic risks can explain half of global mortality and more than one-third of global DALYs providing many opportunities for prevention. Of the larger risks, the attributable burden of high BMI has increased in the past 23 years. In view of the prominence of behavioural risk factors, behavioural and social science research on interventions for these risks should be strengthened. Many prevention and primary care policy options are available now to act on key risks.

Funding

Bill & Melinda Gates Foundation.

Introduction

The Global Burden of Disease, Injuries, and Risk Factor study 2013 (GBD 2013) is the first of a series of annual updates of the GBD. Quantification of functional health loss and mortality by disease and injury is an important input to more informed health policy, as is the contribution of different risk factors to patterns of disease and injury across countries. Risk factor quantification, particularly for modifiable risk factors, can help to identify emerging threats to population health and opportunities for prevention.

The Global Burden of Disease study 2010 (GBD 2010) provided the most comprehensive comparative assessment of risk factors covering 67 risk factors or clusters of risks for 21 regions from 1990 to 2010.1 The GBD comparative risk assessment (CRA) brings together data for excess mortality and disability associated with risk factors, data for exposure to risks, and evidence-based assumptions on the desired counterfactual distribution of risk exposure to estimate how much of the burden observed in a given year can be attributed to risk exposure in that year and in all previous years. GBD 2010 generated broad interest in the scientific community and public health agencies.2, 3, 4 GBD 2010 also generated several scientific debates on topics such as the magnitude of burden related to diet, the low estimates of burden related to unsafe water and sanitation, and exclusion of some risk–outcome pairs from the analysis.2, 5, 6, 7, 8, 9, 10 Additionally, new studies have been published since the release of GBD 2010 that inform both estimates of relative risks and exposure in different countries.11, 12, 13, 14, 15

The GBD 2013 provides a timely opportunity to update each aspect of the CRA with new data for exposure, add new risk–outcome pairs meeting study inclusion criteria, and incorporate new data for relative risks and the appropriate counterfactual risk distribution. Important insights from scientific debates on GBD 2010 have been used in revised approaches. This analysis supersedes all previous GBD CRA results by providing a complete revised time-series of attributable burden from 1990 to 2013, for 188 countries, with consistent definitions and methods. This CRA also allows us to explore how much of the burden of disease around the world is not explained by the behavioural, environmental and occupational, and metabolic risks included in this study.

Section snippets

Overview

In general, this analysis follows the CRA methods used in GBD 2010.1 Conceptually, the CRA approach evaluates how much of the burden of disease observed in a given year can be attributed to past exposure to a risk. Attributable burden is estimated by comparing observed health outcomes to those that would have been observed if a counterfactual level of exposure had occurred in the past. Given that different risks lead to different health outcomes, assessments are undertaken separately for

Results

The risk factors included in this analysis are estimated to account for a widely varying proportion of deaths and DALYs across causes at the global level. Figure 2 uses tree maps to represent the PAFs for all risks combined for each disease and injury for level 2 causes in the GBD hierarchical cause list for deaths and DALYs. Across the level 2 causes, the attributable fractions for deaths range from 0% for neonatal disorders to 88·7% (95% UI 86·6–90·6) for cardiovascular and circulatory

Discussion

Our analysis of 79 risks divided into three broad groups of behavioural, environmental and occupational, and metabolic risk factors shows that together they explain slightly greater than 57% of global deaths and more than 41% of global DALYs. Each of the risk factors included in this analysis is modifiable, pointing to the huge potential of prevention to improve human health. Globally, behavioural risk factors are the most important followed by metabolic and environmental and occupational risk

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