A recent study from London has revealed that smokers and ex-smokers with idiopathic pulmonary fibrosis (IPF), an untreatable progressive lung disease that usually leads to death within a few years of diagnosis, have a worse prognosis than non-smokers.
Contrary to previous research findings suggesting that current smokers with IPF might live longer than ex-smokers, the new results indicate that the data likely reflected a healthy smoker effect
Dr Athol U. Wells, lead researcher from the Interstitial Lung Disease Unit at the Royal Brompton Hospital in London said that current smoking is linked to milder disease.
"Smoking is associated with a higher mortality in IPF, and an earlier finding, suggesting the contrary, was almost certainly due to the fact that smokers tend to stop smoking when disease becomes more severe—and so current smoking is linked to milder disease," said Wells.
The team examined medical records of 249 patients with IPF, and evaluated the degree and severity of their disease, smoking history and survival.
The initial findings when unadjusted for disease severity were similar to the earlier study, which said that smokers had longer survival times than ex-smokers.
However, when they adjusted their data to reflect the extent and severity of the disease the findings gave new insights.
"We established that current smokers live longer, but this is mostly because they have much milder disease. Clearly, many patients stop smoking precisely because their disease is getting worse. This is the 'healthy smoker' effect: that current smoking is a marker for milder disease because advancing disease causes smoking cessation," he said.
"Symptomatic patients with more severe disease may be more likely to stop smoking for perceived health reasons. It can, therefore, be argued that current smoking might be a marker of less severe disease, associated with better survival."
"We speculate as to whether this reflects disease co-morbidity—that is, excess mortality from non-pulmonary disease ascribable to smoking— or an effect of smoking in driving progression of lung disease," he added.
Wells said that if they are able to understand the mechanisms linked to smoking for progression of pulmonary fibrosis this may harbour the possibility new treatment options.
The study is published in the second issue for January of the American Journal of Respiratory and Critical Care Medicine.