Differences in Clinical Characteristics and Outcomes Between Men and Women With Idiopathic Pulmonary Fibrosis: A Multicenter Retrospective Cohort Study

Background: Idiopathic pulmonary fibrosis (IPF) is a disease with a male predominance. Prior data suggest that male sex is associated with disease progression and survival. The basis for this sex difference is unknown. Research Question: Are there differences in clinical disease characteristics and outcomes between men and women with IPF? Study Design and Methods: Two tertiary care center IPF cohorts were pooled to analyze sex differences in outcomes of time to lung transplantation or death. Predictors of outcome that were analyzed included age, FVC % predicted, diffusion capacity for carbon monoxide (DLCO) % predicted, BMI, smoking history, and respiratory variables of cough, phlegm, and need for supplemental oxygen. The associations of these factors with mortality were estimated by sex and then compared using tests for interaction. Results: There were a total of 1,263 patients in the pooled cohort with follow-up data; approximately 71% of the patients were men. Male sex was independently associated with higher risk for death or lung transplantation after adjusting for age, FVC % predicted, and DLCO % predicted (hazard ratio for men, 1.4; 95% CI, 1.2-1.7; P < .001). Older age, lower DLCO % predicted, and presence of cough or phlegm were negatively associated with transplant-free survival in men but not in women, but only the association for cough differed statistically by sex (interaction P = .007). Interpretation: Male sex is associated with worse transplant-free survival in IPF. Cough may be a sex-specific predictor of survival in this population.