WASHINGTON Second-hand smoke worsens lung function in people with cystic fibrosis, especially those with a specific gene, researchers said on Tuesday.
Researchers at Johns Hopkins University School of Medicine in Baltimore showed how genetic and environmental factors can interact to harm lung function in cystic fibrosis patients, said Dr. Garry Cutting who worked on the study.
Cystic fibrosis is an inherited chronic disease that affects the lungs and digestive system of about 30,000 children and adults in the United States, according to the Cystic Fibrosis Foundation.
It causes thick, sticky mucus to build up, leading to life-threatening lung infections and major digestion problems.
The researchers studied 812 people with the disease whose average age was 19 of whom 188 were exposed to second-hand cigarette smoke at home.
Lung function in those exposed to second-hand smoke was reduced by about 10 percent compared to those not exposed, the researchers found. Lung function was determined by how much air a person could breathe out in the first second of expiration.
The researchers then looked at lung function in those who also had a specific version of a gene called TGFbeta1 that affects the severity of this disease and asthma.
Having this gene variant doubled the negative effects of second-hand smoke on lung function, the researchers wrote in the Journal of the American Medical Association.
The research did not look at lung function in people with cystic fibrosis who are active smokers, Cutting said in a telephone interview.
"There really haven't been that many patients with cystic fibrosis who have had active smoking. But there have been a number of anecdotal reports that show that it's absolutely disastrous for them to actively smoke," Cutting said.
(Editing by Maggie Fox and Alan Elsner)