Smoking and idiopathic pulmonary fibrosis: A meta-analysis.

INTRODUCTION: In this study, we aimed to systematically explore the relationship between smoking and idiopathic pulmonary fibrosis (IPF).

METHODS: The PubMed, Web of Science and Embase databases were searched to systematically identify eligible studies. The Newcastle‒Ottawa Quality Assessment Scale (NOS) was used to evaluate the quality of the selected studies. The pooled odds ratio (OR) and survival hazard ratio (HR) were calculated with a random effects model using Stata 16.0 software.

RESULTS: Thirty studies were enrolled. All of the included studies were considered to have intermediate or high quality. Nine studies were suitable for meta-analysis of ORs, and twenty-one studies were suitable for meta-analysis of survival HR. The pooled analysis revealed a significant difference in the risk of IPF between the smoking group and the never smoking group (OR 1.71, 95% CI 1.27-2.30, P < 0.001), indicating that smoking is a risk factor for IPF. When analyzing pooled survival HRs, never smoking was compared to former smoking or current smoking. Former smoking was shown to be a poor prognostic factor for IPF (HR 1.43, 95% CI 1.18-1.74, P < 0.001), but current smoking was not a significant factor.

CONCLUSIONS: Our results indicated that smoking is a risk factor for IPF patients.

IMPLICATIONS: In this study, we mainly concluded that smoking is a risk factor for IPF and that former smoking is a poor prognostic factor for IPF. To our knowledge, this is the first meta-analysis report focusing on the association between smoking per se and IPF. Through our current study, we hope to further raise awareness of the relationship between smoking and IPF.