In 2021, the top 10 causes of death accounted for 39 million deaths, or 57% of the total 68 million deaths worldwide.
The top global causes of death, in order of total number of lives lost, are associated with two broad topics: cardiovascular (ischaemic heart disease, stroke) and respiratory (COVID-19, chronic obstructive pulmonary disease, lower respiratory infections), with COVID-19 emerging as the second leading causes of death globally.
Causes of death can be grouped into three categories: communicable (infectious and parasitic diseases and maternal, perinatal and nutritional conditions), noncommunicable (chronic) and injuries.
Leading causes of death globally
At a global level, 7 of the 10 leading causes of deaths in 2021 were noncommunicable diseases, accounting for 38% of all deaths, or 68% of the top 10 causes.
Leading causes of death in 2021 globally
The world’s biggest killer is ischaemic heart disease, responsible for 13% of the world’s total deaths. Since 2000, the largest increase in deaths has been for this disease, rising by 2.7 million to 9.1 million deaths in 2021. As a newly emerged cause of deaths, COVID-19 was directly responsible for 8.8 million deaths in 2021, and consequently, largely pushed down other leading causes of death by one place. Instead of being the second and third leading causes of death as in 2019, stroke and chronic obstructive pulmonary disease became the third and fourth in 2021, responsible for approximately 10% and 5% of total deaths, respectively.
Lower respiratory infections remained the world’s most deadly communicable disease other than COVID-19, ranked as the fifth leading cause of death. However, the number of deaths has gone down substantially: in 2021 it claimed 2.5 million lives, 370 000 fewer than in 2000.
Deaths from other noncommunicable diseases were also on the rise. Trachea, bronchus and lung cancers deaths have risen from 1.2 million in 2000 to 1.9 million in 2021 and are now ranked sixth among leading causes of death.
In 2021, Alzheimer’s disease and other forms of dementia ranked as the seventh leading cause of death, killing 1.8 million lives. Women are disproportionately affected. Globally, 68% of deaths from Alzheimer’s and other forms of dementia are women.
Diabetes was also among the top 10 causes of death, following a significant percentage increase of 95% since 2000.
Other diseases which were among the top 10 causes of death in 2000 are no longer on the list. HIV and AIDS are among them. Deaths from HIV and AIDS have fallen by 61%, moving from the world’s seventh leading cause of death in 2000 to the twenty-first in 2021. Similarly, deaths due to diarrhoeal diseases have dropped by 45%, from sixth leading cause of death in 2000 to thirteenth in 2021.
In contrast, kidney diseases have risen from the world’s nineteenth leading cause of death to the ninth, with number of deaths increasing by 95% between 2000 and 2021.
Leading causes of death by income group
The World Bank classifies the world's economies into four income groups (1) based on gross national income: low, lower-middle, upper-middle and high.
Leading causes of death in 2021 in low-income countries
People living in a low-income country are far more likely to die of a communicable disease than a noncommunicable disease. Despite the global decline, 8 of the top 10 causes of death in 2021 in low-income countries were communicable diseases.
Malaria, tuberculosis and HIV and AIDS all remain in the top 10. However, they all fell significantly. The biggest decrease among the top 10 deaths in this group has been for HIV and AIDS, with 63% fewer deaths in 2021 than in 2000.
Diarrhoeal diseases are also a significant cause of death in low-income countries: they ranked seventh leading causes of death for this income category in 2021. Nonetheless, diarrhoeal diseases are decreasing, representing the third biggest decrease in fatalities among the top 10 (in low-income countries, falling 38% in 2000 and 2021).
Deaths due to chronic obstructive pulmonary disease are particularly infrequent in low-income countries compared to other income groups. It does not appear in the top 10 for low-income countries yet ranks in the top 10 for all other income groups.
While the top killer in low-income countries was lower respiratory infections in 2021, COVID-19 ranked only the sixth, the lowest ranking of the diseases among all income groupings, killing a total of 258 000 people.
Leading causes of death in 2021 in lower-middle-income countries
Lower-middle-income countries have the most balanced top 10 causes of death: 5 noncommunicable, and 5 communicable, with the new cause COVID-19 topping the list and costing over 4 million lives in 2021. Diabetes is a rising cause of death in this income group: it has moved from the fourteenth to eighth leading cause of death and the number of deaths from this disease has more than doubled since 2000.
As a top 10 cause of death in this income group, tuberculosis and diarrhoeal diseases remain a significant challenge. However, these categories of disease saw substantial decreases in absolute deaths, both falling by about 47% between 2000 and 2021. The biggest increase in absolute deaths is from ischaemic heart disease, rising by more than 1.4 million since 2000 to 3.2 million in 2021. HIV and AIDS have seen the biggest decrease in rank among the previous top 10 causes of death in 2000, moving from seventh to nineteenth.
Leading causes of death in 2021 in upper-middle-income countries
In upper-middle-income countries, there has been a notable rise in deaths from lung cancer, which have increased by 442 000; more than 2.5 times the increase in deaths of all three other income groups combined. In addition, stomach cancer features highly in upper-middle-income countries compared to the other income groups, remaining the only group with this disease in the top 10 causes of death.
Deaths from ischaemic heart disease have increased by more than 1.4 million, the second largest rise in any income group in terms of absolute number of deaths from this cause, just 40 000 lower than the increase in lower-middle-income countries. In 2021, ischaemic heart disease ranked second, closely tracking stroke in total absolute number of deaths and one place ahead of COVID-19.
Other than COVID-19, there is only one communicable disease (lower respiratory infections) in the top 10 causes of death for upper-middle-income countries. It ranked eighth in 2021, down by 3 places since 2000.
Leading causes of death in 2021 in high-income countries
In high-income countries, deaths are increasing for the majority of the top 10 diseases in 2000, primarily due to population ageing. Exceptionally, schaemic heart disease, stroke and stomach cancer are among the causes of death in the top 10 for which the total numbers have gone down between 2000 and 2021 – by 15%, 18% and 19%, respectively. High-income is the only category of income group in which there have been decreasing numbers of deaths from these three diseases. Nonetheless ischaemic heart disease and stroke have remained in the top three causes of death for this income category, with a combined total of over 2.6 million fatalities in 2021. In addition, deaths from hypertensive heart disease are rising. Reflecting a global trend, this disease has more than doubled and risen from the sixteenth leading cause of death in 2000 to the tenth in 2021.
Deaths due to Alzheimer’s disease and other dementias have also increased dramatically, nearly four-fold since 2000. This became the fourth leading cause of death in high-income countries and is on track to overtake stroke as one of the top three.
COVID-19 claimed 1.2 million lives and ranked second in 2021 in high-income countries. As with upper-middle-income countries, only one other communicable disease – lower respiratory infections – appears in the top 10 causes of death.
Why do we need to know the reasons people die?
It is important to know why people die to improve how people live. Measuring how many people die each year helps to assess the effectiveness of our health systems and direct resources to where they are needed most. For example, mortality data can help focus activities and resource allocation in the health sector, as well as in other sectors such as transportation, food and agriculture, and the environment.
COVID-19 has highlighted the importance for countries investing in civil registration and vital statistics systems to allow daily counting of deaths and direct prevention and treatment efforts. It has also revealed inherent fragmentation in data collection systems in most low-income countries, where policy-makers still do not know with confidence how many people die and of what causes.
The World Health Organization develops standards and best practices for data collection, processing and synthesis through the consolidated and improved International Classification of Diseases (ICD-11). This digital platform facilitates reporting of timely and accurate data for causes of death for countries to routinely generate and use health information that conforms to international standards.
The routine collection and analysis of high-quality data on deaths and causes of death, as well as data on disability– disaggregated by age, sex and geographic location – is essential for improving health and reducing deaths and disability across the world.
WHO’s Global Health Estimates, from which the information in this fact sheet is extracted, present comprehensive and comparable health-related data, including life expectancy, healthy life expectancy, mortality and morbidity, and burden of diseases at global, regional and country levels disaggregated by age, sex and cause. The estimates released in 2024 report on trends for more than 160 diseases and injuries annually from 2000 to 2021.
1. The World Bank. World Bank Country and Lending Groups. https://datahelpdesk.worldbank.org/knowledgebase/articles/906519-world-bank-country-and-lending-groups