Epidemiology of asthma

Lore & Background

Asthma prevalence varies dramatically between countries, from 1% to 29%, with higher diagnosis rates in developed nations but more severe health effects in developing countries. In 2019, 96% of asthma deaths and 84% of the asthma burden occurred in low- and middle-income countries. Urbanization, air pollution, unhygienic living conditions, and lack of diagnostic resources contribute to symptom severity in low-resource communities. Within developed countries, asthma is more common among the economically disadvantaged, while in developing countries it may be more prevalent among wealthier individuals, suggesting diverse underlying mechanisms not well understood.

Reader's Guide

Gender differences in asthma are pronounced and change across the lifespan. Before puberty, asthma is more common in boys, possibly due to smaller airway diameters relative to lung volume. After puberty, symptoms increase in girls, and by adulthood, both prevalence and severity are greater in women. Women experience worsening symptoms around menstruation, pregnancy, and menopause, suggesting sex hormones and immune pathway variations play a role. From 1990 to 2021, global age-standardized prevalence decreased by 40.01% and incidence by 29.89%, but this decline occurred predominantly in men; female mortality increased consistently while male mortality remained stable. In the United States, asthma prevalence rose from 7.3% to 8.2% between 2001 and 2009, with continued upward trends through 2021. Females were 1.76 times more likely to have asthma than males, and prevalence was highest among non-Hispanic whites (46.4%), followed by non-Hispanic blacks (26.0%). In the United Kingdom, adult women had higher rates than men, and between 2014-15 and 2019-20, over 5,100 women died from asthma attacks compared with fewer than 2,300 men. In Canada, 2023 age- and sex-standardized prevalence was 12.2% for females and 9.9% for males.

Did You Know?

• In 2023, approximately 363 million people worldwide were affected by asthma, and 442,000 died from the disease.
• From 1990 to 2021, the global prevalence of asthma has generally increased or remained stable, rather than decreasing.
• In the United Kingdom between 2014-15 and 2019-20, more than 5,100 women died from an asthma attack compared with fewer than 2,300 men.
• In the United States, asthma prevalence among children decreased annually from 2010 through 2021, but increased annually for adults from 2013 to 2021.

Global Scale and the Paradox of Wealth

In 2023, roughly 363 million people around the world lived with asthma, and the disease claimed approximately 442,000 lives. Yet the story is not simply one of numbers; it is one of striking geographic and economic contradictions. Asthma is diagnosed more frequently in developed nations, where prevalence rates swing dramatically from as low as 1 percent to as high as 29 percent depending on the country. Paradoxically, it is in low- and middle-income settings that the disease inflicts its harshest toll: in 2019, 96 percent of all asthma-related deaths and 84 percent of the overall disease burden were concentrated in these regions. Within wealthy countries, asthma clusters among economically disadvantaged groups, whereas in poorer nations it skews toward wealthier populations. This inversion hints at multiple, still poorly understood biological pathways. Urbanization, chronic exposure to air pollution, unsanitary living conditions, and the absence of diagnostic tools and affordable treatment all compound the frequency and severity of symptoms in resource-limited communities, turning a manageable condition into a life-threatening one.

The Gender Divide Across a Lifetime

Asthma does not treat all bodies equally, and the pattern shifts dramatically with age. Before puberty, boys are disproportionately affected, a disparity that may be linked to their relatively narrower airway diameters compared with lung volume. As adolescence takes hold, however, the trajectory reverses: girls experience a marked escalation in symptoms, and by adulthood women carry both a higher prevalence and greater severity of the disease than men. Globally, 136 million women live with asthma, representing 57 percent of the 235 million affected individuals. Women also face a higher risk of death from the condition. Hormonal fluctuations tied to the menstrual cycle, pregnancy, and menopause appear to modulate symptom severity, pointing to sex-hormone-driven immune pathways as a key mechanism. The Global Burden of Disease data from 2021 reinforces this: between 1990 and 2021, the overall age-standardized prevalence fell by roughly 40 percent, yet that improvement was concentrated almost entirely in men. Female mortality climbed steadily over the same period while male mortality held nearly flat, underscoring a widening and still-unexplained gap.

Regional Patterns and Attributable Risk Factors

The Global Burden of Disease Study 2021, drawing on data from 204 countries and territories, paints a nuanced regional picture. From 1990 to 2021, the global age-standardized burden of asthma trended downward, with prevalence dropping about 40 percent and incidence falling roughly 30 percent. Yet the distribution of new cases is far from uniform. The highest incidence rates were recorded in South Asia, East Asia, and high-income North America, while the lowest age-standardized incidence per 100,000 appeared in Southern Sub-Saharan Africa, South Asia, and East Asia. The Caribbean and Central Europe posted the highest ASIR values. The study also identified four major attributable risk factors, ranked by global impact: elevated body mass index, occupational exposure to asthmatic triggers, nitrogen dioxide pollution, and smoking. Each of these factors exerts a different weight in different countries, meaning that a single global prevention strategy would be insufficient. The interplay between these modifiable risks and local environmental or economic conditions shapes where asthma is most diagnosed and where it is most lethal.

The American Anomaly

While the global trend points toward declining asthma burden, the United States tells a countervailing story. Asthma was recognized as a major public-health crisis in the 1970s, and rates climbed sharply from the 1960s through 1994. In 1980, only 3.6 percent of American children had asthma; by 2001 that figure had nearly tripled to 9 percent. Unlike much of the world, the U.S. has sustained an upward trajectory in both age-standardized prevalence and disability-adjusted life years from 1990 to 2021. A National Health and Nutrition Examination Survey analysis covering adults from 1999 to 2020 found that 8.7 percent of the adult population had asthma, with those aged 60 and older showing the highest rate at 34 percent. Women were 1.76 times more likely to be affected than men, and obese individuals faced a 1.74-fold increase compared with underweight peers. Ethnic disparities are stark: non-Hispanic whites reported the highest prevalence at 46.4 percent, followed by non-Hispanic blacks at 26 percent. In 2021, over 22 million Americans, including 6 million children, were hospitalized 500,000 times for asthma, making exacerbations one of the leading causes of pediatric emergency visits.

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