Washington (USA): Does asthma run in your family? Depending on how many relatives are affected and how close they are, your risk of asthma could be up to six times higher than the average person's, according to a report in the May issue of Genetics in Medicine, the official peer-reviewed journal of The American College of Medical Genetics. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals, and institutions in medicine, nursing, allied health, pharmacy and the pharmaceutical industry.

"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," conclude lead author Tiebin Liu and colleagues of The US Centers for Disease Control and Prevention.

The researchers analyzed 1999 to 2004 data on 1,500 adults (20 or older) from the National Health and Nutrition Examination Survey (NHANES) study. Based on the number and closeness of relatives with asthma, participants were classified as being at high, moderate, or average risk of asthma. About two percent of people were at high risk and thirteen percent at moderate risk; the remaining 85 percent were at average risk.

Asthma prevalence increased from 9.4 percent for people at average risk, to 20.4 percent for those at moderate risk, to 37.6 percent for those at high risk. Asthma risk was 2.5 times higher in the moderate-risk group and 5.8 times higher in the high-risk group.

After adjustment for other factors, risk was 2.4 times higher in the moderate-risk group and 4.8 times higher in the high-risk group, compared to people at average risk. Other asthma risk factors included African American race, low income, obesity, smoking or living with a smoker, and physical inactivity.

Asthma occurred at younger ages in people with a family history. Average age at onset decreased from 22 years in the average-risk group, to 19 years in the medium-risk group, to 17 years in the high-risk group.

Asthma is a major public health problem, affecting an average 34 million Americans. Many previous studies have sought to identify asthma risk factors, but most have focused on children. Although asthma clearly runs in families, the true impact of family history on asthma risk, especially in adults, has been unclear.

The new study suggests that asthma risk is at least two times higher in people with a moderate family history (for example, one parent or sibling with asthma), and up to six times higher for those with a strong family history (for example, both parents affected). The results may be helpful in identifying asthma earlier—especially in adults, in whom asthma is commonly overlooked. The authors call for more research into the role of family history in diagnosing asthma, and whether this information can help to reduce the disease's harmful effects.