Risk Factors

PART 1 Risk Factors You Can’t Control

Research Report

Do you have to...

Gender. Before puberty, three times as many boys as girls have asthma; during adolescence, the prevalence is equal. When asthma first occurs during adulthood, it’s more common in women than in men.

Genetics. Asthma has a strong genetic component. People with a parent who has asthma are three to six times more likely to develop asthma than someone who doesn’t have a parent with asthma. But the genetics of asthma are very complicated: over 100 genes are thought to be associated with asthma, and more are still being found. These genes interact with each other and also with the environment in creating asthma.

It seems that many modest risk factors work together in creating susceptibility, and environmental factors are equally as important as genetic factors in determining if someone will develop asthma. But the exact mechanism by which these factors lead to asthma is still unknown.

Atopy (allergic hypersensitivity). Atopy is an inherited tendency to develop the classic allergic diseases: eczema, hay fever, and atopic asthma (asthma triggered by exposure to an allergen). About half of children with eczema develop asthma.

A mother who smoked during pregnancy. Infants born to mothers who smoked during pregnancy tend to have lower lung function than babies born to mothers who didn’t smoke, leading to the development of asthma.

Premature birth. It’s theorized that premature babies have a higher risk of developing asthma due to a common complication of pregnancy: chorioamnionitis, an inflammation of the fetal membranes and amniotic fluid due to bacterial infection. Chorioamnionitis is linked to more than half of all preterm births.

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PART 2 Risk Factors That Can Be Managed

Obesity. There’s a strong association between obesity and asthma, and the risk of asthma rises with increased BMI and waist circumference. The reasons for this connection aren’t well understood.

Smoking. A number of studies have shown that smoking is an important risk factor for asthma. In addition, teenagers who smoke are more likely to develop asthma later.

Secondhand smoke exposure. Exposure to secondhand smoke is an important risk factor for developing asthma, especially for children.

Exposure to environmental pollutants and irritants. Environmental pollutants and irritants can be found both indoors and outdoors:
- Indoor pollutants and irritants include gas from gas stoves (which contains nitrogen oxides), mold and mildew, household cleaners and paints, dust mites, cockroaches, and animal dander.
- Outdoor pollutants and irritants include pollen and dust as well as air pollution and the harmful gases it contains, such as sulfur dioxide, nitrogen oxides, and ozone.

Exposure to hazardous chemicals at work. Occupational risk factors for asthma include exposure to harmful substances such as hairspray, paint fumes, industrial chemicals, or chemicals used in pesticides and fertilizers.

Taking nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDS, including aspirin, ibuprofen, and naproxen, are a risk factor for aspirin-induced asthma (AIA), which often develops after a viral infection.

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Photo credit: Dust mite
Copyright 2010 Gilles San Martin

Photo credit: Pregnant smoker
Copyright 2010 Andrew Vargas

Photo credit: Man sneezing
Copyright 2009 James Gathany