Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks for 195 countries and territories, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017

Abstract

Background: The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 comparative risk assessment (CRA) is a comprehensive approach to risk factor quantification that offers a useful tool for synthesising evidence on risks and risk-outcome associations. With each annual GBD study, we update the GBD CRA to incorporate improved methods, new risks and risk-outcome pairs, and new data on risk exposure levels and risk-outcome associations.

Methods: We used the CRA framework developed for previous iterations of GBD to estimate levels and trends in exposure, attributable deaths, and attributable disability-adjusted life-years (DALYs), by age group, sex, year, and location for 84 behavioural, environmental and occupational, and metabolic risks or groups of risks from 1990 to 2017. This study included 476 risk-outcome pairs that met the GBD study criteria for convincing or probable evidence of causation. We extracted relative risk and exposure estimates from 46 749 randomised controlled trials, cohort studies, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. Using the counterfactual scenario of theoretical minimum risk exposure level (TMREL), we estimated the portion of deaths and DALYs that could be attributed to a given risk. We explored the relationship between development and risk exposure by modelling the relationship between the Socio-demographic Index (SDI) and risk-weighted exposure prevalence and estimated expected levels of exposure and risk-attributable burden by SDI. Finally, we explored temporal changes in risk-attributable DALYs by decomposing those changes into six main component drivers of change as follows: (1) population growth; (2) changes in population age structures; (3) changes in exposure to environmental and occupational risks; (4) changes in exposure to behavioural risks; (5) changes in exposure to metabolic risks; and (6) changes due to all other factors, approximated as the risk-deleted death and DALY rates, where the risk-deleted rate is the rate that would be observed had we reduced the exposure levels to the TMREL for all risk factors included in GBD 2017.

Findings: In 2017, 34·1 million (95% uncertainty interval [UI] 33·3-35·0) deaths and 1·21 billion (1·14-1·28) DALYs were attributable to GBD risk factors. Globally, 61·0% (59·6-62·4) of deaths and 48·3% (46·3-50·2) of DALYs were attributed to the GBD 2017 risk factors. When ranked by risk-attributable DALYs, high systolic blood pressure (SBP) was the leading risk factor, accounting for 10·4 million (9·39-11·5) deaths and 218 million (198-237) DALYs, followed by smoking (7·10 million [6·83-7·37] deaths and 182 million [173-193] DALYs), high fasting plasma glucose (6·53 million [5·23-8·23] deaths and 171 million [144-201] DALYs), high body-mass index (BMI; 4·72 million [2·99-6·70] deaths and 148 million [98·6-202] DALYs), and short gestation for birthweight (1·43 million [1·36-1·51] deaths and 139 million [131-147] DALYs). In total, risk-attributable DALYs declined by 4·9% (3·3-6·5) between 2007 and 2017. In the absence of demographic changes (ie, population growth and ageing), changes in risk exposure and risk-deleted DALYs would have led to a 23·5% decline in DALYs during that period. Conversely, in the absence of changes in risk exposure and risk-deleted DALYs, demographic changes would have led to an 18·6% increase in DALYs during that period. The ratios of observed risk exposure levels to exposure levels expected based on SDI (O/E ratios) increased globally for unsafe drinking water and household air pollution between 1990 and 2017. This result suggests that development is occurring more rapidly than are changes in the underlying risk structure in a population. Conversely, nearly universal declines in O/E ratios for smoking and alcohol use indicate that, for a given SDI, exposure to these risks is declining. In 2017, the leading Level 4 risk factor for age-standardised DALY rates was high SBP in four super-regions: central Europe, eastern Europe, and central Asia; north Africa and Middle East; south Asia; and southeast Asia, east Asia, and Oceania. The leading risk factor in the high-income super-region was smoking, in Latin America and Caribbean was high BMI, and in sub-Saharan Africa was unsafe sex. O/E ratios for unsafe sex in sub-Saharan Africa were notably high, and those for alcohol use in north Africa and the Middle East were notably low.

Interpretation: By quantifying levels and trends in exposures to risk factors and the resulting disease burden, this assessment offers insight into where past policy and programme efforts might have been successful and highlights current priorities for public health action. Decreases in behavioural, environmental, and occupational risks have largely offset the effects of population growth and ageing, in relation to trends in absolute burden. Conversely, the combination of increasing metabolic risks and population ageing will probably continue to drive the increasing trends in non-communicable diseases at the global level, which presents both a public health challenge and opportunity. We see considerable spatiotemporal heterogeneity in levels of risk exposure and risk-attributable burden. Although levels of development underlie some of this heterogeneity, O/E ratios show risks for which countries are overperforming or underperforming relative to their level of development. As such, these ratios provide a benchmarking tool to help to focus local decision making. Our findings reinforce the importance of both risk exposure monitoring and epidemiological research to assess causal connections between risks and health outcomes, and they highlight the usefulness of the GBD study in synthesising data to draw comprehensive and robust conclusions that help to inform good policy and strategic health planning.

Funding: Bill & Melinda Gates Foundation.

Copyright © 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.

Figures

Figure 1

Relationship between age-standardised summary exposure values and SDI for three of the top environmental and occupational, behavioural, and metabolic risk factors by number of attributable DALYs globally The three leading risks for each Level 1 risk group are shown, except alcohol (fourth leading behavioural risk), which was included for variety instead of short gestation for birthweight. Each point corresponds to the age-standardised SEV in a country for males (blue), females (red), or both sexes (purple) for SEVs that are not sex specific. Points depict all country-years, 1990–2017. Lines show the expected SEV by SDI for each sex. Note that the y-axis scales differ by risk to correspond to the range of observed SEVs. DALYs=disability-adjusted life-years. SDI=Socio-demographic Index. SEV=summary exposure value.

Figure 2

Leading 15 Level 4 risk factors by attributable DALYs at the global level, 1990, 2007, and 2017, for both sexes (A), females (B), and males (C) Risks are connected by lines between time periods; solid lines are increases and dashed lines are decreases. Statistically significant increases or decreases are shown in bold (p

Figure 3

Percentage change in risk-attributable DALYs at the global level in 2007–17, due to population growth, population ageing, changes in exposure to Level 1 risk factors, and changes in risk-deleted DALY rates, for females, males, and both sexes Results are shown for all causes combined, CMNNDs, NCDs, and injuries. The black dot on each bar shows total percentage change. The risk-deleted DALY rate is the expected DALY rate if the exposure level for all risk factors were reduced to the theoretical minimum risk exposure level. Changes in the risk-deleted rate might result from changes in risks and risk–outcome pairs that are not currently included in the Global Burden of Diseases, Injuries, and Risk Factors Study or changes in other factors such as treatment. The change in CMNNDs and injuries due to metabolic risk exposure for both males and females is not zero but is too small to visualise because of the small number of risk–outcome pairs. CMNNDs=communicable, maternal, neonatal, and nutritional diseases. DALYs=disability-adjusted life-years. NCDs=non-communicable diseases.

Figure 4

Percentage change in the absolute number of all-cause risk-attributable DALYs for both sexes, by location, 2007–17 Changes due to population growth (A), population ageing (B), changes in risk-deleted DALY rates (C), changes in exposure to environmental and occupational risk factors (D), changes in exposure to behavioural risk factors (E), and changes in exposure to metabolic risk factors (F). The risk-deleted DALY rate is the expected DALY rate if the exposure level for all risk factors were reduced to the theoretical minimum risk exposure level. Changes in the risk-deleted rate might result from changes in risks and risk–outcome pairs not included in the Global Burden of Diseases, Injuries, and Risk Factors Study or changes in other factors such as treatment. ATG=Antigua and Barbuda. DALYs=disability-adjusted life-years. FSM=Federated States of Micronesia. Isl=Islands. LCA=Saint Lucia. TLS=Timor-Leste. TTO=Trinidad and Tobago. VCT=Saint Vincent and the Grenadines.

Figure 4

Percentage change in the absolute number of all-cause risk-attributable DALYs for both sexes, by location, 2007–17 Changes due to population growth (A), population ageing (B), changes in risk-deleted DALY rates (C), changes in exposure to environmental and occupational risk factors (D), changes in exposure to behavioural risk factors (E), and changes in exposure to metabolic risk factors (F). The risk-deleted DALY rate is the expected DALY rate if the exposure level for all risk factors were reduced to the theoretical minimum risk exposure level. Changes in the risk-deleted rate might result from changes in risks and risk–outcome pairs not included in the Global Burden of Diseases, Injuries, and Risk Factors Study or changes in other factors such as treatment. ATG=Antigua and Barbuda. DALYs=disability-adjusted life-years. FSM=Federated States of Micronesia. Isl=Islands. LCA=Saint Lucia. TLS=Timor-Leste. TTO=Trinidad and Tobago. VCT=Saint Vincent and the Grenadines.

Figure 4

Percentage change in the absolute number of all-cause risk-attributable DALYs for both sexes, by location, 2007–17 Changes due to population growth (A), population ageing (B), changes in risk-deleted DALY rates (C), changes in exposure to environmental and occupational risk factors (D), changes in exposure to behavioural risk factors (E), and changes in exposure to metabolic risk factors (F). The risk-deleted DALY rate is the expected DALY rate if the exposure level for all risk factors were reduced to the theoretical minimum risk exposure level. Changes in the risk-deleted rate might result from changes in risks and risk–outcome pairs not included in the Global Burden of Diseases, Injuries, and Risk Factors Study or changes in other factors such as treatment. ATG=Antigua and Barbuda. DALYs=disability-adjusted life-years. FSM=Federated States of Micronesia. Isl=Islands. LCA=Saint Lucia. TLS=Timor-Leste. TTO=Trinidad and Tobago. VCT=Saint Vincent and the Grenadines.

Figure 5

Trends in the ratios of observed SEVs to SEVs expected based on SDI, by super-region, for both sexes, 1990–2017 Trends are for three of the top environmental (A), behavioural (B), and metabolic (C) risk factors by number of attributable DALYs globally. Observed to expected ratios are based on age-standardised SEVs. y-axes are on a log scale with the range scaled appropriately for each risk factor. DALYs=disability-adjusted life-years. SDI=Socio-demographic Index. SEV=summary exposure value.

Figure 6

Expected relationship between all-age, all-cause risk-attributable DALY rates and SDI for each GBD Level 2 risk, 1990–2017 Stacked curves show males (left) and females (right) after adjusting for mediation, scaling to account for overlapping risks, and aggregating so that total expected DALY rates reflect the true all-cause total expected DALY rates attributable to all risk factors. The y-axis shows lowest SDI (0·09) to highest SDI (0·92) for all GBD countries and territories, 1990–2017. Coloured regions are the proportion of the total attributable DALY rate corresponding to that risk factor. DALYs=disability-adjusted life-years. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study. LDL=low-density lipoprotein. SDI=Socio-demographic Index.

Figure 7

Leading five risk factors for DALYs with the ratio of observed to expected DALYs based on Socio-demographic Index, by super-region and region, and by sex, 2017 Number below each risk factor is its observed to expected ratio. Ratios are based on age-standardised DALY rates. BMI=body-mass index. DALYs=disability-adjusted life-years. Ergonomic=occupational ergonomic factors. FPG=fasting plasma glucose. LDL=low-density lipoprotein. Household air=household air pollution from solid fuels. Kidney=impaired kidney function. Low birthweight=low birthweight for gestation. PM=particulate matter pollution. SBP=systolic blood pressure. Short gestation=short gestation for birthweight. Wasting=child wasting. Water=unsafe water source. *Round brackets indicate excluded endpoints whereas square brackets indicate included endpoints.

Figure 8

Ratios of observed to expected attributable DALY rates based on Socio-demographic Index for each Level 1 risk for both sexes by location, 2017 Ratios for environmental and occupational risk factors (A), behavioural risk factors (B), and metabolic risk factors (C). Observed to expected ratios are based on age-standardised DALY rates.ATG=Antigua and Barbuda. DALYs=disability-adjusted life-years. FSM=Federated States of Micronesia. Isl=Islands. LCA=Saint Lucia. TLS=Timor-Leste. TTO=Trinidad and Tobago. VCT=Saint Vincent and the Grenadines.

Figure 8

Ratios of observed to expected attributable DALY rates based on Socio-demographic Index for each Level 1 risk for both sexes by location, 2017 Ratios for environmental and occupational risk factors (A), behavioural risk factors (B), and metabolic risk factors (C). Observed to expected ratios are based on age-standardised DALY rates.ATG=Antigua and Barbuda. DALYs=disability-adjusted life-years. FSM=Federated States of Micronesia. Isl=Islands. LCA=Saint Lucia. TLS=Timor-Leste. TTO=Trinidad and Tobago. VCT=Saint Vincent and the Grenadines.