# Genetic association between smoking and DLCO in idiopathic pulmonary fibrosis patients

## TL;DR

This study finds that smoking is linked to reduced lung function in patients with idiopathic pulmonary fibrosis, suggesting quitting smoking could help slow disease progression.

## Contribution

The study uses Mendelian randomization to provide evidence of a causal link between smoking and decreased DLCO in idiopathic pulmonary fibrosis patients.

## Key findings

- A genetically predicted increase in smoking index was associated with decreased DLCO in IPF patients.
- The inverse-variance weighting analysis showed a statistically significant association (ORIVW = 0.54; 95% CI 0.32–0.93; P = 0.02).
- Sensitivity analyses confirmed the robustness of the observed association.

## Abstract

Observational studies have shown that smoking is related to the diffusing capacity of the lungs for carbon monoxide (DLCO) in individuals with idiopathic pulmonary fibrosis (IPF). Nevertheless, further investigation is needed to determine the causal effect between these two variables. Therefore, we conducted a study to investigate the causal relationship between smoking and DLCO in IPF patients using two-sample Mendelian randomization (MR) analysis.

Large-scale genome-wide association study (GWAS) datasets from individuals of European descent were analysed. These datasets included published lifetime smoking index (LSI) data for 462,690 participants and DLCO data for 975 IPF patients. The inverse-variance weighting (IVW) method was the main method used in our analysis. Sensitivity analyses were performed by MR‒Egger regression, Cochran’s Q test, the leave-one-out test and the MR-PRESSO global test.

A genetically predicted increase in LSI was associated with a decrease in DLCO in IPF patients [ORIVW = 0.54; 95% CI 0.32–0.93; P = 0.02].

Our study suggested that smoking is associated with a decrease in DLCO. Patients diagnosed with IPF should adopt an active and healthy lifestyle, especially by quitting smoking, which may be effective at slowing the progression of IPF.

The online version contains supplementary material available at 10.1186/s12890-024-02974-2.