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Smoke worsens lung function in cystic fibrosis patients

30/01/2008

Secondhand smoke can worsen lung function in people with cystic fibrosis, with the effect worse in those with a specific gene variation, researchers say.

The team from Johns Hopkins Medical Institute argue their study is the first to uncover the genetic evidence that inhaling secondhand smoke worsens lung disease.

One gene variation is said to weaken lung function as well as shorten the lifespan of those affected by cystic fibrosis (CF) and those who are also exposed to secondhand smoke.

This variation doubles the negative effects of secondhand smoke in these people.

"It's always been suspected that secondhand smoke is detrimental to lung disease patients, and now we have a handle on one specific gene that clearly makes it worse for those with CF," said Dr Garry Cutting.

The researchers studied 812 people with CF, 188 of which were exposed to secondhand smoke at home.

Publishing their findings in the Journal of the American Medical Association, the scientists say any secondhand smoke exposure reduced lung function by ten per cent.

They also compared patient lung function with their particular genetic variant of CF as well as the genetic variant of another gene, TGFbeta1.

This variant has been shown to affect the severity of CF and asthma.

CF patients who also carried particular TGFbeta1 mutations had twice as bad lung function when exposed to secondhand smoke compared with those who were not exposed.

The researchers conclude that secondhand smoke exposure is roughly the equivalent to seven years of lung function decline.

"This means that a 17-year old CF patient with a TGFbeta1 mutation and exposed to secondhand smoke would have lung function similar to that of a 24-year-old who wasn't exposed to secondhand smoke," said Dr Cutting.

"This gene-environment interaction drastically accelerates reduced lung function."