Asthma affects an estimated 262 million people worldwide, cutting across every age, sex, and background. In the United States alone, roughly 25 million people currently have asthma, including about 4.7 million children. While anyone can develop asthma, certain groups carry a significantly higher burden based on age, sex, race, genetics, occupation, and body weight.
Age: Not Just a Childhood Disease
Asthma is often thought of as a childhood condition, but adults actually make up the vast majority of cases. About 8% of U.S. adults have current asthma compared with 6.5% of children. The age breakdown reveals some surprises: asthma is relatively uncommon in very young children (1.9% of those under 5), then rises sharply once kids reach school age. Teenagers and young adults ages 15 to 24 have some of the highest rates, around 9.5%. Prevalence stays fairly steady through middle age at about 8%, then dips slightly to 7.2% among adults 65 and older.
Many people develop asthma for the first time as adults, a pattern called adult-onset asthma. This form tends to be less driven by allergies and more connected to factors like hormonal changes, workplace exposures, or respiratory infections.
How Sex and Hormones Shift the Pattern
The relationship between sex and asthma flips at puberty. Before puberty, boys have higher asthma rates than girls (roughly 11.9% versus 7.5%) and are twice as likely to be hospitalized for an asthma attack. Boys have narrower airways relative to their lung size, which makes them more prone to symptoms. They also tend to have stronger allergic immune responses early in life.
Around age 10, when girls begin puberty, the pattern reverses. Girls’ asthma symptoms climb steadily as they progress through puberty while boys’ symptoms decline. By adulthood, women have asthma at notably higher rates than men (9.6% versus 6.3%) and are three times more likely to be hospitalized for an asthma-related event. This hormonal connection also helps explain why some women notice their asthma worsens around their menstrual cycle or during pregnancy.
Racial and Ethnic Disparities
Some of the starkest differences in who asthma affects fall along racial lines, and they reflect deep inequities in housing, air quality, healthcare access, and environmental exposures. Black Americans bear a disproportionate burden at every level: prevalence, emergency visits, hospitalizations, and deaths.
Black children are 60% more likely than U.S. children overall to have asthma, with a prevalence of 10.3% compared to 6.5% nationally. Black adults are 14% more likely than adults overall to have the condition. But the gap widens dramatically when it comes to severe outcomes. Black adults are more than twice as likely to die from asthma as adults overall, and Black children are nearly four times as likely. Emergency department visits tell a similar story: Black adults visit the ER for asthma at nearly three times the national rate, and Black children at about two and a half times the rate.
These disparities aren’t explained by biology alone. They’re driven by higher exposure to air pollution, older housing with mold and pest allergens, neighborhoods near highways or industrial sites, and reduced access to preventive care and specialist treatment.
Family History and Genetic Risk
Asthma runs in families, and the parent who has it matters. A large cohort study tracking children from birth through adolescence found that having a mother with asthma raises a child’s risk more than having a father with asthma. At age 3, children of asthmatic mothers had an absolute risk increase of 10.7 percentage points compared to children with no asthmatic parents. Children of asthmatic fathers had a 5.3 percentage point increase.
When both parents have asthma, the risks roughly add up in early childhood, with a 16.8 percentage point increase at age 3 and 16.7 at age 7. By age 14, though, the combined effect diminishes, dropping to about 9.7 percentage points, closer to the maternal-only effect. The stronger maternal link likely reflects a combination of shared genetics, exposures during pregnancy, and the in-utero environment shaping a child’s developing immune system and lungs.
Income and Where You Live
Poverty is one of the strongest predictors of asthma. People in the lowest income brackets have notably higher rates: 9.8% prevalence for households earning under $15,000 per year compared with 5.9% for those earning above $75,000. Low-income housing is more likely to contain triggers like cockroach droppings, mold, dust mites, and secondhand smoke. People with fewer resources also have less access to consistent medical care, meaning their asthma is more likely to go uncontrolled.
The relationship between urban and rural environments is more complicated than people assume. In the U.S., asthma is somewhat more common in urban areas (7.1%) than rural ones (5.7%), likely due to air pollution and crowded housing conditions. Baltimore, for instance, has had asthma hospitalization rates for children more than double the national average. But the picture isn’t universal. Some studies have found higher asthma rates in rural communities, particularly in low-income rural regions like the Mississippi Delta. Internationally, the urban-rural divide varies by country, with urban environments in China, India, and Brazil showing higher rates, while parts of Turkey and Europe have reported higher rural prevalence.
Workplace Exposures
Work-related asthma is far more common than most people realize. Up to 48% of adult asthma cases may be related to the workplace, meaning the job either caused the asthma or makes existing asthma worse. That translates to roughly 2.7 million U.S. workers whose breathing problems are tied to what they inhale on the job.
Healthcare and social assistance workers have some of the highest rates, with 10.7% prevalence overall and healthcare support roles reaching as high as 21.5% in some states. Cleaning chemicals, latex, and disinfectants are common triggers in these settings. Other high-risk industries include manufacturing (exposure to chemicals, dust, and fumes), agriculture (grain dust, pesticides, animal proteins), and construction (wood dust, paint fumes, isocyanates in spray coatings). Bakeries, auto body shops, and hair salons also carry elevated risk due to flour dust, paint compounds, and chemical products.
Obesity and Asthma Severity
Carrying excess weight significantly increases both the risk of developing asthma and the severity of existing asthma. The relationship runs in both directions: obesity can trigger new-onset asthma, and having asthma can make it harder to stay active, which contributes to weight gain. Regardless of which came first, people with obesity-related asthma consistently have worse symptom control, more frequent flare-ups, and lower quality of life. Their asthma also tends to respond less well to standard treatments, making it one of the more difficult forms to manage.
Excess weight puts mechanical pressure on the lungs and airways, reducing how deeply you can breathe. Fat tissue also produces inflammatory signals that keep the airways in a heightened state of irritation. For some people, losing even a moderate amount of weight leads to measurable improvements in breathing and fewer asthma attacks.