The Global Burden of Disease (GBD) is the largest and most comprehensive effort to measure health loss across the world, tracking hundreds of diseases, injuries, and risk factors in over 200 countries going back to 1990. While the World Health Organization (WHO) partners on the project, the study itself is led by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington and published in The Lancet. The most recent full analysis, GBD 2021, covers 371 diseases and injuries and 88 risk factors, producing estimates that governments and health organizations use to set priorities and allocate funding.
What the GBD Actually Measures
The central metric of the GBD is the disability-adjusted life year, or DALY. One DALY equals one year of healthy life lost, either through dying early or living with illness or disability. It combines two components: years of life lost (YLLs), calculated by multiplying deaths by the life expectancy remaining at the age of death, and years lived with disability (YLDs), calculated by multiplying the number of people living with a condition by a “disability weight” that reflects how severe it is. A disability weight of 0 means perfect health; 1 means a state equivalent to death.
This framework lets researchers compare vastly different health problems on the same scale. A fatal disease in young people generates many YLLs. A chronic condition like low back pain that rarely kills but affects millions generates enormous YLDs. By summing both, DALYs capture the full picture of a population’s health in a single number.
Who Runs It and How They Work Together
The GBD study is led by IHME, founded and directed by Professor Chris Murray. WHO collaborates through a formal memorandum of understanding, contributing data, publishing GBD estimates in its own policy documents, and helping countries identify gaps in their health data systems. IHME and WHO share data, metadata, and analytical methods with each other and encourage countries to make their data publicly available through WHO databases and the Global Health Data Exchange.
The data feeding the GBD comes from five main source types: population censuses, civil registration and vital statistics systems (death certificates, essentially), household surveys, health management information systems, and public health surveillance systems. In countries with strong record-keeping, the estimates are precise. In countries without reliable death registration, the study relies more heavily on surveys and statistical modeling, which introduces uncertainty that the researchers quantify and report.
The World’s Biggest Killers
Ischemic heart disease is the world’s leading cause of death, responsible for 13% of all deaths globally. It has also seen the largest absolute increase since 2000, rising by 2.7 million deaths to reach 9.0 million in 2021. COVID-19, as a newly emerged cause, was directly responsible for 8.7 million deaths that same year.
The broader pattern over the past two decades is a shift in what kills people. Noncommunicable diseases like heart disease, stroke, diabetes, and Alzheimer’s now dominate, while infectious diseases have receded. HIV has dropped out of the global top 10 causes of death. Lower respiratory infections remain the deadliest communicable disease after COVID-19, ranked fifth overall in 2021, though total deaths from these infections have declined. Alzheimer’s disease and diabetes have entered the top 10, reflecting aging populations worldwide.
The Shift From Infectious to Chronic Disease
In 2002, noncommunicable diseases accounted for roughly 59% of all deaths worldwide, while communicable diseases, maternal and newborn conditions, and nutritional deficiencies accounted for about 32%. Injuries made up the remaining 9%. When measured in DALYs rather than deaths alone, the gap narrows because infectious diseases disproportionately affect children, generating more years of life lost per death. By that measure, noncommunicable diseases represented about 47% of the global burden and communicable conditions about 41%.
This transition has been especially sharp in developing countries. Diabetes saw a sixfold increase globally between 1985 and 2005, jumping from 30 million to 180 million cases. Nearly 80% of cardiovascular disease deaths now occur in developing countries. Projections have estimated that between 2000 and 2020, chronic disease cases would increase by 73% in developing countries compared to 29% in developed ones. Many low- and middle-income nations now face a “double burden,” dealing with persistent infectious diseases while chronic conditions surge.
Risk Factors Driving the Burden
The GBD doesn’t just track diseases. It also quantifies how much of the burden is attributable to specific risk factors. By the GBD 2010 study, researchers were systematically measuring 67 risk factors across all regions, and the latest cycle covers 88. The dominant risks have shifted in the same direction as the diseases themselves: away from infectious-disease drivers and toward high blood pressure, smoking, and poor diet.
Between 2000 and 2021, the health burden attributable to behavioral risks (like smoking and alcohol use) decreased by about 21%, and the burden from environmental and occupational risks fell by 22%. But DALYs attributable to metabolic risks, including high blood sugar, high cholesterol, and obesity, increased by 49%. That divergence reflects the combined effect of aging populations, more sedentary lifestyles, and diets higher in processed food and sugar spreading across the globe.
How the Burden Differs by Region
Where you live dramatically shapes your health risks. The GBD uses a Socio-demographic Index (SDI) that combines income, education, and fertility rates to group countries. In low-SDI regions, age-standardized death rates from injuries alone are 2.5 times higher than in high-SDI regions: roughly 89 per 100,000 people compared to 35 per 100,000. The DALY rate follows the same pattern, nearly doubling from about 2,264 per 100,000 in high-income regions to 4,526 per 100,000 in low-income ones.
Countries like Afghanistan, the Central African Republic, and Lesotho report the highest age-standardized death rates, while Singapore, Spain, and Italy record the lowest. One counterintuitive finding: high-income regions actually report the highest rates of diagnosed injuries and prevalent conditions, likely because better healthcare systems detect and record more cases. Lower-middle-income regions report the lowest incidence, not because people are healthier, but because many conditions go undiagnosed.
Why It Matters for Policy
The GBD’s value lies in making health problems comparable. Without it, a government might allocate resources based on whichever disease gets the most public attention rather than which one causes the most suffering. By converting every disease, injury, and risk factor into the same unit (DALYs), policymakers can see that investing in blood pressure management might prevent more healthy years lost than spending the same amount on a rarer but more dramatic condition.
WHO uses GBD estimates in its own policy documents and works with IHME to help countries strengthen their health data systems. The collaboration supports the development of better tools for decision-making and guides national policy discussions. For countries with weak data infrastructure, the GBD can reveal health burdens that were previously invisible, simply because no one was counting. The estimates are updated regularly, creating a running scorecard that shows whether health investments are working or whether new threats are emerging faster than old ones are being controlled.