Ischaemic heart disease killed more people than any other condition on the planet in 2021, holding a grim title it has carried for more than two decades. But the full picture of global mortality is more complex than a single disease at the top of a list. A combination of chronic conditions, resurgent infections, and pandemic aftershocks now forms a web of threats that claimed tens of millions of lives in a single year, with the heaviest toll falling on populations least equipped to fight back. Data compiled in the World Health Organization’s leading causes series show that the top 10 causes alone accounted for 39 million deaths in 2021, underscoring how concentrated the burden has become.
Heart Disease and Stroke Still Dominate
Cardiovascular diseases remain the single largest category of death worldwide. An estimated 19.8 million people died from cardiovascular conditions, according to the World Health Organization. Within that category, ischaemic heart disease, which results from narrowed arteries starving the heart of blood, has been the number one killer globally for the period spanning 2000 through 2021. Stroke follows closely behind. Together, these two conditions account for the largest share of the 39 million deaths attributed to the top 10 causes of death in 2021, a group that represented 57% of the 68 million total global deaths that year. This dominance reflects not just aging populations but also persistent exposure to tobacco, unhealthy diets, and sedentary lifestyles in both rich and poor countries.
What makes cardiovascular mortality so persistent is its deep entanglement with other chronic conditions. Diabetes, for instance, was the direct cause of 1.6 million deaths in 2021, but its downstream effects push the real toll much higher. Roughly 530,000 kidney disease deaths that year were caused by diabetes, and approximately 11% of cardiovascular deaths are attributable to high blood glucose, according to the WHO diabetes fact sheet. With 830 million people now living with diabetes globally, the pipeline feeding cardiovascular mortality is widening rather than narrowing. This feedback loop between metabolic disease and heart failure means that progress against one condition without addressing the other yields diminishing returns, particularly in health systems where screening and long-term management remain patchy or unaffordable.
Cancer and COPD: Slow Killers With Massive Reach
Cancer claimed nearly 10 million lives globally in 2020, with 19.3 million new cases diagnosed across 185 countries and 36 cancer types, according to the International Agency for Research on Cancer GLOBOCAN 2020 estimates. Lung cancer ranked among the leading causes of death in the WHO Global Health Estimates for 2021, a position it has held for years thanks in large part to tobacco use and delayed diagnosis. Colorectal, liver, stomach, and breast cancers round out the deadliest subtypes. Updated primary mortality data for cancers beyond the 2020 GLOBOCAN cycle is not yet available from vital registration systems in many high-burden regions, which means the true current toll could be higher than these figures suggest, especially where screening programs were disrupted by the pandemic.
Chronic obstructive pulmonary disease sits just behind, ranking as the fourth leading cause of death worldwide. COPD killed 3.5 million people in 2021, accounting for approximately 5% of all global deaths, according to the WHO COPD fact sheet. The disease carries a disproportionate burden among people under age 70 in low- and middle-income countries, where exposure to household air pollution from cooking fuels and poor tobacco regulation accelerate lung damage earlier in life. Unlike heart disease, which benefits from a relatively broad toolkit of interventions such as statins, blood pressure control, and surgical procedures, COPD treatment options in resource-limited settings remain thin, and prevention depends heavily on tobacco control frameworks that many governments have been slow to enforce. This combination of limited treatment and weak prevention creates a slow-burning epidemic of breathlessness and disability that culminates in premature death.
COVID-19 Disrupted a Decade of Progress
Before the pandemic, noncommunicable diseases dominated global mortality in a pattern that had been solidifying for years. Ischaemic heart disease, stroke, cancers, COPD, diabetes, and dementias were the primary drivers. COVID-19 broke that trajectory. The virus became a leading cause of death globally in both 2020 and 2021, ranking among the top killers and, according to the WHO’s recent life expectancy analysis, eliminating a decade of progress in global life expectancy. The pandemic did not simply add deaths to the ledger. It disrupted healthcare systems, delayed diagnoses for cancer and cardiovascular disease, and diverted resources from tuberculosis and malaria programs, particularly in countries already struggling with limited hospital capacity and fragile supply chains.
That disruption had a compounding effect. Noncommunicable diseases still killed at least 43 million people in 2021, equivalent to 75% of non-pandemic deaths, but many of those deaths were worsened by deferred care during lockdowns and overwhelmed hospitals. Alzheimer’s disease and other dementias also continued climbing the rankings, reflecting aging populations in wealthier nations and better survival from acute conditions earlier in life. The conventional framing that separates infectious diseases from chronic ones obscures the real dynamic: COVID-19 worsened outcomes for people already living with diabetes, heart disease, and lung conditions, creating a collision between pandemic mortality and the chronic disease burden that was already the world’s biggest killer. As updated figures from the WHO’s broader mortality estimates database continue to emerge, they are likely to show how far-reaching these indirect effects have been.
Tuberculosis and Malaria Strike Back
Among infectious diseases, tuberculosis has reclaimed the top position. A total of 1.23 million people died from TB in 2024, including 150,000 among people with HIV, with 10.7 million new incident TB illnesses recorded that year, according to the WHO’s updated tuberculosis fact sheet. These figures reflect not only ongoing transmission but also the lingering impact of COVID-19 disruptions, which reduced access to diagnostic services and interrupted treatment courses in many countries. Drug-resistant TB remains a particular concern, as treatment is longer, more toxic, and more expensive, further straining health systems that are already under pressure from noncommunicable disease care.
The burden of TB is highly concentrated. According to the WHO’s latest TB mortality analysis, a small group of high-incidence countries accounts for the majority of deaths, many of them in settings where poverty, overcrowding, and limited access to primary care fuel ongoing transmission. Malaria, while not detailed in the same set of figures here, has followed a similar pattern of resurgence, particularly in sub-Saharan Africa, where vector control programs and routine prevention campaigns were disrupted during the pandemic years. The result is that diseases once thought to be on a clear downward trajectory have stalled or reversed, adding another layer of risk in regions already grappling with high rates of HIV, maternal mortality, and child undernutrition.
Interlocking Crises and the Path Forward
Viewed together, the data from cardiovascular disease, cancer, chronic respiratory illness, COVID-19, TB, and other infections reveal an interlocking set of crises rather than isolated problems. The same structural forces (poverty, weak primary care, inadequate surveillance, and commercial determinants such as tobacco and ultra-processed foods) drive multiple leading causes of death at once. Countries that struggle to finance routine immunization and basic diagnostics are also those where hypertension goes undetected, diabetes is poorly controlled, and TB spreads unchecked. As the WHO’s ongoing global health estimates are updated, they are expected to show that without integrated strategies, the world will continue to trade one dominant cause of death for another rather than reducing overall mortality.
Responding effectively will require more than disease-specific campaigns. Investments in primary health care, reliable vital registration, and affordable access to essential medicines can simultaneously reduce deaths from heart disease, diabetes, COPD, and TB. Stronger tobacco control and cleaner household energy can cut both cancer and respiratory mortality, while resilient health systems can maintain TB and malaria services even during future pandemics. The picture painted by recent mortality data is sobering, but it also points to clear leverage points: strengthening the foundations of health systems and addressing shared risk factors offer the best hope of bending the global death curve downward across multiple leading killers at once.
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*This article was researched with the help of AI, with human editors creating the final content.
