A team of Korean researchers discovered that cigarette smoking significantly increases the risk of developing idiopathic pulmonary fibrosis (IPF), according to a study published in Thorax. The association between smoking and IPF was clear enough for a dose-response relationship to be observed. 

Medical researchers have long tried to establish the exact pathophysiology of IPF. A prevailing theory is that it is caused by repeated injuries to the pulmonary epithelium, which eventually causes defects in the healing process.

If that theory is correct, it follows that cigarette smoking is likely a major risk factor for the development of IPF since studies have proven that smoking injures pulmonary tissue, according to the researchers of this study. However, “data on the association between smoking quantity and IPF incidences are scarce,” they wrote.

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The researchers decided to conduct a study to research the effects that smoking status and amount have on the development of IPF. They used the Korean National Health Information Database to recruit IPF patients who were seen between 2009 and 2012.

Through this methodology, they identified 25,113 IPF patients, which constituted 0.11% of the total patients registered in the database. The researchers then collected information regarding the smoking status and history of these patients through a questionnaire. 

The results of this study demonstrated that the risk of developing IPF was significantly higher in patients who were either former or current smokers. For former smokers, the risk of developing IPF compared to patients who never smoked was 1.41-fold higher in men and 1.62-fold higher in women.

For current smokers, the risk of developing IPF compared to patients who never smoked was 1.74-hold higher in men and 1.90-fold higher in women. In addition, both smoking intensity as measured in packs per day and smoking duration demonstrated a dose-dependent relationship in the development of IPF. 

The methodology employed in this study involved using a large national health database and allowed it to demonstrate “the causal relationship between smoking and the development of IPF more clearly than previous cross-sectional and case-control studies,” the authors said.


Bae W, Lee C, Lee J, et al. Impact of smoking on the development of idiopathic pulmonary fibrosis: results from a nationwide population-based cohort study. Thorax. Published online September 30, 2021. doi:10.1136/thoraxjnl-2020-215386