Asthma affects about 25 million Americans, but it doesn’t strike evenly across the population. Your risk depends on a mix of genetics, biology, environment, and life circumstances. Some groups, including children born prematurely, people with a family history, women over 40, and those living in low-income urban neighborhoods, face significantly higher odds than others.
Children vs. Adults: How Age Shapes Risk
Asthma is one of the most common chronic diseases in children, and it often begins before age five. Boys are more likely than girls to develop asthma during childhood, partly because boys have smaller airways relative to lung size during early development. But this pattern flips after puberty. By adulthood, women develop new asthma at nearly twice the rate of men, with an annual incidence rate of 1.39% versus 0.77% in one long-running study. By age 40, the majority of women with asthma have the adult-onset form rather than a condition that started in childhood.
This shift appears to be driven in part by reproductive hormones, though obesity and smoking also play a role. Notably, obesity, lack of allergies, and a history of smoking each increase the proportion of adult-onset disease among women but not men. So while childhood asthma skews male, the adult picture is overwhelmingly female.
Genetics and Family History
If one of your parents has asthma, your risk of developing it is about 25%. If both parents have it, that jumps to roughly 50%. These numbers make asthma one of the more heritable chronic conditions, though no single gene is responsible. Dozens of genes contribute, most of them involved in how your immune system responds to allergens and irritants or how your airways develop and repair themselves.
Genetics alone don’t determine whether you’ll get asthma. They set a threshold. Whether you cross it depends on environmental exposures, infections, weight, and other factors that interact with your inherited vulnerability.
Race, Ethnicity, and Socioeconomic Gaps
CDC data from 2019 to 2021 show stark disparities. American Indian and Alaska Native populations have the highest asthma prevalence at 12.3%, followed by Black Americans at 10.9% and people of multiple races at 10.3%. White Americans fall at 7.6%, Hispanic Americans at 6.4%, and Asian Americans at 4.1%.
These numbers reflect more than biology. Decades of housing policy, particularly the racist practice of redlining, concentrated communities of color in neighborhoods with aging housing stock, heavy traffic, proximity to industrial sites, and limited access to healthy food. Children in these low-income urban areas face higher exposure to mold, mice, cockroach allergens, secondhand smoke, and outdoor air pollution, all of which worsen asthma risk and outcomes. Studies have found that children in lower-income households and non-white families have higher levels of tobacco smoke byproducts in their urine, which correlate with worse symptoms and more frequent asthma attacks.
Poverty itself is independently associated with higher asthma rates. Experiencing discrimination, exposure to violent crime, and lower caregiver education levels all increase healthcare use for children with asthma, suggesting that chronic stress compounds the physical exposures.
Premature Birth and Early Infections
Babies born early face a significantly higher risk of asthma that can persist into their teens and beyond. The earlier the birth, the greater the risk. Infants born before 32 weeks of gestation are about four times more likely to develop asthma compared to full-term babies. Those born between 33 and 36 weeks carry about 1.7 times the risk.
Low birth weight adds its own layer. Babies born weighing less than about 2.2 pounds (1,000 grams) are 1.8 times more likely to need asthma medications later in childhood. The underlying issue is that premature lungs haven’t finished developing, leaving airways more vulnerable to infection and inflammation.
Early respiratory infections compound the problem. Bronchiolitis in the first year of life, particularly when caused by rhinovirus (the common cold virus), is strongly linked to later asthma. Children who develop rhinovirus-related wheezing in infancy have dramatically elevated odds of asthma compared to those who don’t. Hospital admission for any respiratory infection in the first year also raises the risk.
The Allergy Connection
Asthma, eczema, food allergies, and hay fever tend to travel together in what doctors call the atopic march. The pattern typically begins with eczema in infancy, followed by food allergies, then hay fever, and finally asthma. About 28% of people with eczema go on to develop asthma. The risk is highest when eczema appears early in life alongside sensitivity to common allergens like dust mites, pet dander, or certain foods.
Not every child with eczema will develop asthma, and not every asthma case follows this progression. But if your child has eczema and tests positive for allergen sensitivities by age one, their likelihood of having asthma by age three rises substantially.
Air Pollution and Where You Live
Traffic-related air pollution is one of the strongest environmental risk factors for new asthma cases in children. An estimated 13% of childhood asthma cases worldwide are attributable to traffic pollution. Particulate matter, nitrogen dioxide, and ozone all contribute, with long-term exposure during early childhood linked to higher asthma incidence through age 20.
Secondhand smoke exposure carries a similar risk profile, and it’s more common in low-income households. The combination of indoor smoke and outdoor pollution in urban areas creates a compounding effect that helps explain why asthma rates are so much higher in disadvantaged neighborhoods.
Obesity and Metabolic Health
Carrying excess weight raises your odds of developing asthma. A large meta-analysis of over 300,000 adults found that overweight individuals were 1.5 times more likely to develop asthma, while those with obesity faced 1.9 times the risk. That translates to roughly 250,000 new asthma cases per year in the U.S. linked to excess weight.
The connection isn’t just mechanical (extra weight compressing the lungs, though that plays a role). Fat tissue, especially in the abdomen, produces inflammatory signals that affect the airways. People with obesity and asthma have more inflammation in their fat tissue compared to people with obesity alone. Metabolic problems like insulin resistance and high blood sugar may also damage airway lining and promote airway narrowing. Interestingly, this form of asthma often responds poorly to standard inhaled steroids, likely because the inflammation driving it is fundamentally different from allergic asthma.
Maternal obesity matters too. Women who are obese during pregnancy or who gain excessive weight while pregnant have a 15 to 30% increased risk of their child developing asthma. Changes to the gut microbiome may be involved: obesity reduces populations of beneficial gut bacteria that produce compounds helping to regulate immune responses, and a similar bacterial imbalance has been found in the lungs of people with asthma.
Workplace Exposures
Occupational asthma accounts for a meaningful share of new adult cases. Certain industries carry well-documented risks, particularly those involving regular exposure to dust, chemical fumes, cleaning compounds, and industrial vapors. Bakers exposed to flour dust, painters working with spray coatings, healthcare workers using latex gloves or cleaning agents, and woodworkers inhaling sawdust are among those most commonly affected. In some cases, a single large exposure to an irritant can trigger a condition called reactive airways dysfunction syndrome, which produces asthma-like symptoms that persist long after the exposure ends.
Adult Women Over 40
Adult-onset asthma has a distinct profile from the childhood version. It’s less likely to involve allergies, more likely to be linked to obesity, and disproportionately affects women. Data from the CARDIA study, which followed participants for two decades, found that adult-onset asthma became the dominant form among women by age 40. Among obese, non-allergic, or ever-smoking women, that crossover happened even younger.
Hormonal factors likely play a role, though the exact mechanisms aren’t fully mapped. What’s clear is that if you’re a woman who never had asthma as a child, you’re not in the clear. New-onset asthma in midlife is common and often goes undiagnosed because both patients and doctors associate asthma with childhood.