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.

被动吸烟使囊肿纤维化的人的肺功能变坏，尤其是那些有特异基因的人。科研人员在周二的时候这样说。

巴尔的摩的约翰霍普金斯大学医学院的科研人员演示了基因和环境因素如何相互影响囊肿纤维化患者的肺功能。正在从事这项研究的高利卡特博士这样说。

囊肿纤维化是一种遗传性的慢性疾病，根据囊肿纤维化基金的结果，它影响着美国大约3万的儿童和成人的肺和消化系统。

它产生厚重粘稠的粘液产生堵塞作用，导致危及生命的肺部感染和严重的消化道问题。

科研人员研究了812例患有这种疾病的患者，他们的平均年龄19岁。其中有188例患者有家庭的被动吸烟史。

研究人员发现，和那些没有被动吸烟的患者相比，那些被动吸烟的患者肺功能大约下降了10%。肺功能的判定用第一秒呼气量来衡量。

然后研究人员又观察了那些有特异TGFbeta1基因型的患者的肺功能。TGFbeta1能够影响这种疾病及哮喘性疾病的严重性。

拥有这种基因变异体对肺功能的负面影响是被动吸烟对肺功能影响的二倍。研究人员将这一点写进了在美国医学协会的杂志上。

研究人员没有观察那些主动吸烟的囊肿纤维化患者的肺功能。卡特在电话接见的时候说。

没有太多的囊肿纤维化的患者是主动吸烟的。但是有一些有趣的报道表明，主动吸烟对他们来说是绝对有损害的。卡特说。