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New Data and Projections on the Global Burden of Disease

Minimized bar diagram on annual deaths from major global challenges.

The recently completed version of the Global Burden of Disease (GBD) Study provides global, national and sub-national estimates for 2021 on many health categories: life expectancy, 288 causes of death, 88 risk factors, incidence and prevalence of 371 diseases and injuries, losses of healthy life-years and projections by 2050. Furthermore, it appears to be the biggest scientific study ever in terms of numbers of topics, estimates produced, collaborators and computational power utilized.

Key findings reveal that COVID-19 was a setback in global health bigger than anticipated, causing a loss in life expectancy by approximately 1.6 years globally and reversing historical trends. In 2020, the total number of deaths worldwide surged by around 10.8% compared to 2019, rising from 57.0 million to 63.1 million deaths. This trend persisted in 2021, with a further 7.5% increase relative to 2020, reaching 67.9 million deaths. For the most part, this excess mortality is related to the COVID-19 pandemic (see source 1, pp. 1989, 2010).

Despite the pandemic, the decline in child mortality continued, albeit at a slower pace. In 2021, there were approximately 4.66 million global deaths among children under 5 years old, a decrease from the 5.21 million deaths in 2019 (source 1, p. 1989).

Estimates of Current Global Health Impacts

We present selected findings of the GBD study related to global challenges that mainly stem from limited access to vital resources such as food, clean air or healthcare. Among these topics, COVID-19 emerged as the leading cause of death in 2021. Here are the results in order of magnitude:

On COVID-19, the GBD study estimates that approximately 7.89 million deaths in 2021 were directly due to SARS-CoV-2 infection, while an additional 2.69 million resulted from other factors associated with the pandemic, such as overburdened health systems. This death toll decreased substantially in 2022 and 2023, with projected direct deaths of 2.40 million and 1.40 million, respectively, establishing COVID-19 as the largest or second-largest infectious killer globally.

All data refers to 2021 unless otherwise stated.
Data source: Global Burden of Disease (GBD) 2021 Study, published in 2024 (Institute for Health Metrics and Evaluation 2024: GBD 2021 fact sheets; GBD 2021 Causes of Death Collaborators 2024: Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990-2021: a systematic analysis for the Global Burden of Disease Study 2021. In: The Lancet, vol. 403, No. 1044; Institute for Health Metrics and Evaluation 2024: GBD Results Tool, GBD Foresight Visualization (on COVID-19 in 2022 and 2023) – for the online tools, a registration is required).
All disease and injury categories (direct causes of death) are distinct, but risk factors (such as child and maternal undernutrition) overlap with other categories.
Outdoor air pollution is a risk factor for human health, to which the study attributed 4.72 million deaths worldwide in 2021.
Indoor air pollution, caused by burning solid fuels inside without proper ventilation systems, was linked to 3.11 million deaths in 2021.
Child and maternal undernutrition claimed the lives of 2.57 million children.
Pneumonia, influenza and other lower respiratory infections (except COVID-19) caused 2.18 million deaths.
Neonatal disorders took the lives of 1.83 million newborns.
Lead pollution was responsible for 1.54 million deaths.
Occupational diseases and accidents were estimated to have 1.44 million workers succumbed to them.
Secondhand smoke accounted for a death toll of 1.29 million people.
Unsafe water, unsafe sanitation and lacking access to a handwashing facility triggered enteric or diarrhoeal diseases that killed 1.22 million people.
Road traffic accidents resulted in 1.20 million deaths.
Hepatitis B and C caused 1.17 million deaths, primarily through related liver cancer and cirrhosis.
Tuberculosis (TB) killed 1.16 million people. Among them, 115 000 people died from resistant strains of the bacteria.
Malaria led to 748 000 deaths, predominantly among children.
HIV/AIDS resulted in 718 000 deaths, including 18 300 from resistant forms of the virus.
Exposure to unhealthy high temperatures is a risk factor that partially captures the disease burden attributable to climate change. Since 1990, the death toll due to prolonged high temperatures has increased by 196 000 lives. About 36 000 lives were lost due to waves of extreme temperature.
Maternal disorders caused the death of 191 000 women and girls.
Adverse effects of medical treatment are estimated to have claimed the lives of 122 000 patients.
Armed conflict, terrorism, police conflict and executions led to an estimated 109 000 deaths in 2021.
Intimate partner violence against women and childhood sexual abuse were responsible for 73 400 deaths.
Measles killed 56 000 people.
Natural disasters are estimated to have resulted in 9430 deaths in 2021 (for data sources, see underneath the diagram).

As mentioned earlier, the GBD study estimates deaths from resistant types of TB and HIV (totalling 133 000 deaths in 2021). Unfortunately, the study does not comprehensively assess antimicrobial resistance, although a previous GBD report estimated about 1.27 million deaths attributable to it in 2019. This figure includes mortality from resistant E.coli, S aureus, K pneumoniae and other pathogens (see source 9).

Projections on Future Global Health Impacts

The latest version of the GBD study offers projections for health-related topics up to 2050. A reference scenario outlines the most likely future based on past trends. It forecasts continued increases in global life expectancy, from 73.6 years in 2022 to around 78.2 years in 2050. However, the rate of improvement will slow down compared to the three decades preceding the COVID-19 pandemic (source 5, p. 2220).

Projections are also provided for direct causes of death: From 2022 to 2050, lower respiratory infections (such as pneumonia and influenza) are projected to increase in the number of deaths by more than half. Smaller increases are expected for enteric/diarrheal diseases, road traffic deaths, adverse effects of medical treatment, environmental heat and cold exposure, natural disasters and conflicts. Decreases are forecasted for TB and malarial deaths; neonatal and maternal disorders will almost halve their number of deaths, and AIDS deaths are projected to more than halve (source 5, appendix 2, table S4). As far as the causes of death coincide with targets of the UN Sustainable Development Goals (SDGs), none of these targets are expected to be achieved by 2030. Only one of them – ending preventable neonatal mortality – may be met by 2050, according to the data by the GBD reference scenario.

Three alternative scenarios have also been set up. They assume a stepwise removal of certain risk factors for human health by 2050:

In a scenario for improved childhood nutrition and vaccination, childhood malnutrition is assumed to linearly decrease to zero by 2050 – no chronic hunger of children anymore. Vaccine coverage against diphtheria, tetanus, pertussis, measles, Haemophilus influenzae type b (Hib), pneumococcal disease and rotavirus will reach 100% in 2050.
In a safer environment scenario, exposure to unsafe water, unsafe sanitation, lack of access to handwashing facilities as well as household air pollution are also to be eliminated by 2050. Based on a pathway for reaching carbon neutrality in 2050, outdoor air pollution and exposure to high temperature will decrease accordingly.
A scenario on improved behavioural and metabolic risks assumes that smoking, unhealthy diets, high adult body mass index (BMI), high systolic blood pressure, high cholesterol and high fasting plasma glucose will be eliminated worldwide by 2050 – no tobacco epidemic and no overweight and obesity anymore (source 5, p. 2209).

The assumptions regarding malnutrition, air pollution as well as unsafe water and sanitation resemble targets of the Sustainable Development Goals, except for the target year (2050 instead of 2030) and that ending hunger is limited to children. Anyway, the authors consider many of their assumptions on the removal of risk factors to be unrealistic but useful as a tool to show relationships between different interventions and outcomes.

At the same time, the alternative scenarios do not assume any reductions in direct causes of death such as those incorporated in the Sustainable Development Goals to end the epidemics of AIDS, tuberculosis, malaria and neglected tropical diseases or to end preventable deaths of children under 5. Meeting such internationally agreed reduction targets is not factored in, neither by 2030 nor by 2050. So the ambition of the alternative scenarios exhibits surprising selectivity. The same applies to their capability to demonstrate potential outcomes. This selectivity in ambition and capability arises from a methodological choice to limit the alternative scenarios to changes in risk factors, which may not be appropriate for describing possible future pathways realistically and comprehensively. Moreover, this limitation results in undesirable consequences.

Despite the extremely ambitious assumptions regarding risk factor removal, two out of the three alternative scenarios do not lead to remarkable reductions in the global burden of disease by 2050. However, when combined, all three alternative scenarios project a gain of 5.3 years in global life expectancy compared to the reference scenario (source 5, p. 2241). Doubling the progress achieved through accelerating current trends is indeed noteworthy. However, two out of the three alternative scenarios only contribute a small proportion to this progress. “We observed the largest scenario differences between the reference scenario and the Improved Behavioural and Metabolic Risks scenario … . The impacts of the two other scenarios compared with the reference scenario were much smaller” (source 5, p. 2245). This follows from three facts:

The chosen indicators life expectancy and lost healthy-life years do not immediately reflect changes in human health, they incorporate mortality-related time-lags (e.g. in comparison with incidence or prevalence).
The Improved Behavioural and Metabolic Risks scenario encompasses six risk factors, with five of them ranking among the top ten in terms of lost healthy life-years (DALYs) in 2021. The other two alternative scenarios cover only two to four risk factors (counting child vaccine coverage as a risk factor), with each having only one or two in the top ten list (source 4, p. 2172). Furthermore, undernutrition and unsafe water/sanitation affect impoverished people, while unhealthy diets etc. are widespread among wealthy and poor people, thus affecting a broader demographic. Hence, issues of different size in distribution are compared directly without addressing this (e.g. by using the rates for DALYs, mortality or prevalence). An effect should be seen in relation to the issue to be solved, and it is not surprising, if a more extended endeavour leads to a more extended effect.
Many risk factors only exhibit long-term impacts on human health, due to cumulative long-term exposure effects. This applies, for example, more markedly to air pollution than to behavioral and metabolic risk factors. Air pollution and heat exposure will also not change substantially in the short or mid-term in a scenario for carbon neutrality, since remaining carbon dioxide emissions are assumed to be captured and stored, so air pollution will still be produced, and the impact on global temperatures will be substantial only in the long-term. Consequently, the benefits of a stepwise reduction in such risk factors will materialize only with a time-lag of decades – primarily after 2050.

These factors are overlooked in a dangerously misguided conclusion by the authors: “Our alternative scenarios thus suggest that … policies that lead to substantial reductions in metabolic risk exposure and rates of tobacco smoking have the potential to reduce the global burden of disease to a greater extent than policies that lead to similarly substantial improvements in rates of childhood malnutrition and vaccination” (source 5, p. 2245). Seeing the potential consequences of such statement, the authors make haste to note that “the seemingly moderate impact of this scenario relative to the gains already projected in the reference scenario reflects past successes in this area, and a failure to continue the interventions that led to past progress could lead to less future progress than we forecast” (ibd.). However, what likely may remain from these alternative scenarios is the problematic impression that social and environmental measures would have smaller positive health impacts than measures promoting behavioural changes in diets, physical activity and smoking.

Such a view, which derives from a major study originally intended to guide priorities in public health, could be detrimental to tackling global issues like unsafe water, air pollution or chronic hunger. When allocating resources for public health and development aid, effectiveness and cost-efficiency play pivotal roles. As stated, the study's results and conclusions would likely have been different if they had considered not only risk factors but direct causes of death (which often have more immediate effects) in the changes outlined for the alternative scenarios. The same applies if the long-term impacts triggered by changes that occurred before 2050 had been included (as it is good practice in studies on climate change). Furthermore, the comparison of the three alternative scenarios faces additional complexities, including differences in feasibility, costs, policy types, and acceptance. While the authors noted that these factors are not addressed in the scenarios, they did not mention that this may put into question the comparisons they made.

Despite such weaknesses at certain points that should be resolved, the GBD study overall provides useful estimates and projections on global health. For over twenty years, it forms an indispensable tool for data-based assessments of major global challenges.

Sources

GBD 2021 Demographics Collaborators: Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950-2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021. In: The Lancet, vol. 403, No. 10440, March 11, 2024 (www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)00476-8/fulltext).
GBD 2021 Causes of Death Collaborators: Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990-2021: a systematic analysis for the Global Burden of Disease Study 2021. In: The Lancet, vol. 403, No. 1044, April 3, 2024 (www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)00367-2/fulltext).
GBD 2021 Diseases and Injuries Collaborators: Global incidence, prevalence, years lived with disability (YLDs), disability-adjusted life-years (DALYs), and healthy life expectancy (HALE) for 371 diseases and injuries in 204 countries and territories and 811 subnational locations, 1990-2021: a systematic analysis for the Global Burden of Disease Study 2021. In: The Lancet, vol. 403, No. 1044, April 17, 2024 (www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)00757-8/fulltext).
GBD 2021 Risk Factors Collaborators: Global burden and strength of evidence for 88 risk factors in 204 countries and 811 subnational locations, 1990-2021: a systematic analysis for the Global Burden of Disease Study 2021. In: The Lancet, vol. 403, No. 1044, May 18, 2024 (www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)00933-4/fulltext).
GBD 2021 Forecasting Collaborators: Burden of disease scenarios for 204 countries and territories, 2022-2050: a forecasting analysis for the Global Burden of Disease Study 2021. In: The Lancet, vol. 403, No. 1044, May 18, 2024 (www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)00685-8/fulltext) (supplementary appendix 2: www.thelancet.com/cms/10.1016/S0140-6736(24)00933-4/attachment/222cc2f6-c88f-4b15-9754-71959c84261b/mmc2.pdf).
Institute for Health Metrics and Evaluation 2024: GBD 2021 disease, injury, and risk factsheets (www.healthdata.org/research-analysis/diseases-injuries-risks/factsheets).
Institute for Health Metrics and Evaluation 2024: GBD 2021 Results Tool (vizhub.healthdata.org/gbd-results/) (registration required).
Institute for Health Metrics and Evaluation 2024: GBD 2021 Foresight Visualization (vizhub.healthdata.org/gbd-foresight/) (registration required).
GBD Antimicrobial Resistance Collaborators: Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis. In: The Lancet, vol. 399, No. 10325, January 19, 2022 (www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02724-0/fulltext).

Suggested citation:
Global2030: New Data and Projections on the Global Burden of Disease. Berlin, Global Challenges Initiative e.V., May 2024. (www.global2030.net/news/new_global_burden_of_disease_data_2024.html).