THURSDAY, April 23 (HealthDay News) -- Adults with a family history of asthma are up to six times more likely to develop the disease than an average person, say U.S. Centers for Disease Control and Prevention researchers.

They analyzed data on 1,500 adults, aged 20 and older, and classified them as being at average, moderate or high risk of asthma based on the number of closeness of relatives with asthma. The researchers found that 85 percent of people were at average risk, 13 percent at moderate risk, and 2 percent at high risk.

Asthma prevalence was 9.4 percent among those at average risk, 20.4 percent for those at moderate risk, and 37.6 for those at high risk. Asthma risk was 2.4 times higher for those at moderate risk and 4.8 times higher for those at high risk, compared to those at average risk.

After they adjusted for other factors, the researchers found that asthma risk was 2.4 times higher in the moderate-risk group and 4.8 times higher in the high-risk group. Other asthma risk factors included being black, obesity, low income, smoking or living with a smoker, and physical inactivity.

Average onset of asthma was 22 years in the average-risk group, 19 years in the moderate-risk group, and 17 years in the high-risk group.

"Our findings showed that a family history of asthma is an important risk factor for asthma, and that familial risk assessments for asthma can help identify people at highest risk for developing asthma," concluded lead author Tiebin Liu and colleagues.

The study is published in the May issue of Genetics in Medicine.

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