Association between smoking and prognosis in idiopathic pulmonary fibrosis: A systematic review and meta-analysis

BACKGROUND: Although smoking is a well-established risk factor for idiopathic pulmonary fibrosis (IPF) development, its impact on clinical outcomes remains unclear. RESEARCH QUESTION: Is smoking associated with clinical outcomes of IPF? METHODS: A systematic search of PubMed, Embase, and the Cochrane Library was conducted to identify studies reporting associations between smoking status and IPF outcomes, including mortality, acute exacerbation (AE), lung cancer development, and baseline lung function. Summary estimates with 95% confidence intervals (CIs) were pooled using random-effects model. Subgroup analyses were conducted by study region. RESULTS: Forty-nine studies comprising 32 974 patients were included. Overall mortality did not differ by smoking status. However, significant regional differences were observed, with ever smokers demonstrating higher mortality in non - East Asian studies (Hazard ratio [HR] 1.17, 95% CI: 1.03-1.33) but lower mortality in East Asian studies (HR 0.75, 95% CI: 0.62-0.91, p-for-interaction < 0.001) compared with never smokers. Current smokers had a higher risk of developing lung cancer compared with non-current smokers (HR 1.88, 95% CI: 1.24-2.87). No significant associations were observed between smoking and the risk of AEs or baseline forced vital capacity. CONCLUSION: Smoking was not associated with overall mortality in IPF, although significant regional differences were observed.