Risk factors

The number of people with asthma is on the rise, with approximately 20 million Americans affected, 9 million of whom are under the age of 18. Although the exact causes of asthma are unknown, scientists have identified risk factors that make it more likely that a person will have asthma. They include the following:

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• Having a parent with asthma
• Exposure to air pollution, as is common in large urban areas
• Exposure to secondhand tobacco smoke
• Exposure to chemicals or other substances on the job that can lead to occupational asthma
• Low birth weight
• Obesity
• Sinusitis
• Acid reflux, or gastroesophageal reflux disease (GERD)
• Living in the inner city, which may actually be a combination of other risk factors, including exposure to air pollution and low birth weight

This section includes more on:

• Occupational asthma
• Sinusitis
• GERD