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Study: air pollution and high blood pressure are the main health risks
Last reviewed: 02.07.2025
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A recent study published in The Lancet estimates relative health risks, exposure levels and disease burden as part of the Global Burden of Disease, Injuries and Risk Factors (GBD) study 2021.
The COVID-19 pandemic has highlighted significant differences in health at the individual and geographic levels due to multiple risk factors and differences in health systems around the world.
Carefully conducted meta-analyses of risk factors can inform public policy about emerging or persistent health problems and identify notable areas of societal progress in health. To inform these analyses, GBD estimates relative health risks by exposure level, risk factor impacts, and the disease burden attributable to multiple risk factors.
Several other research networks, such as the NCD Risk Factor Collaboration (NCD-RisC), have provided valuable population-level and multi-country data on specific risk factors. However, only GBD systematically analyses multiple risk factors in 204 countries and territories worldwide. For example, between 1990 and 2021, GBD analysed 88 risk factors in 204 countries and 811 subnational locations.
The current study summarizes the methods adopted in the GBD 2021. It presents estimates of exposure levels for 88 risk factors and risk factor combinations, and the relationship of these risk factors to health outcomes. Data were extracted from 54,561 different sources to create epidemiological estimates, with estimates obtained for 631 risk factor-outcome pairs.
The association between a risk factor and an outcome was data-driven, and sex-, age-, location-, and year-specific estimates were calculated at regional, national, and global levels. Relative risks (RRs) of a given outcome were estimated for a given risk factor.
Summary exposure values (SEVs) measured the prevalence of risk-adjusted exposure. In addition, for each risk factor, theoretically minimal risk exposure levels (TMRELs) were used to calculate the population-attributable fraction (PAF). The risk factor burden was the product of the PAF and the disease burden, expressed in units of disability-adjusted life years (DALYs).
Particulate air pollution was identified as the main contributor to the global disease burden in 2021, accounting for 8% of total DALYs. The next key contributor was high systolic blood pressure (SBP), which accounted for 7.8% of total DALYs. Smoking, low birth weight, short gestation, and high fasting plasma glucose (FPG) contributed 5.7%, 5.6%, and 5.4% of total DALYs, respectively.
For infants and children under 14 years, the main risk factors were unsafe water, low birth weight, short gestation, handwashing and sanitation. For older cohorts, the key risk factors were high body mass index (BMI), FPG, SBP and low-density lipoprotein (LDL) cholesterol levels.
Between 2000 and 2021, there was a marked shift in global health concerns. During this period, the decline in all age-specific DALYs can be attributed to a 20.7% reduction in behavioural risks and a 22% reduction in environmental and occupational risks. This was accompanied by an almost 50% increase in DALYs attributable to high metabolic risks.
The current study identified several risk factors that have not been adequately addressed. Linking disease burden to risk factors is important as it can aid prioritization when resources are limited.
The main limitation of the 2021 GBD was the exclusion of several potentially important risk factors. For example, the significant impact of the COVID-19 pandemic was not formally integrated or quantified.
Another notable limitation of the study is the variable quality of data and inconsistent availability. The lack of data made it difficult to estimate RRs given the presence of significant heterogeneity across a range of socioeconomic factors.
In the future, the GBD should expand the coverage of risk factors, particularly for outcomes that contribute significantly to disease burden, such as mental disorders and musculoskeletal conditions. Mental disorders account for 5.4% of global DALYs, yet only 8% of mental disorders were attributed to risk factors. Similarly, musculoskeletal conditions account for 5.6% of the global burden; however, in the current GBD, only 20.5% of this burden was attributable to risk factors.