Introduction:
Asthma and chronic obstructive pulmonary disease (COPD) are two common respiratory ailments with an overlapping pathogenesis.

Material and methods:
In this study, using a two-sample Mendelian randomization (MR) approach and analyzing publicly available genome-wide association study (GWAS) datasets, we explored the causal impact of asthma on the onset of COPD.

Results:
Using genetic instrumental variables associated with asthma (p < 5 × 10–8) and applying multiple MR methods (IVW, MR-Egger, and weighted median), we identified a significant causal relationship between asthma and COPD. The inverse variance weighted (IVW) method indicated that asthma increases the risk of developing COPD with an odds ratio (OR) of 1.35 (95% confidence interval [CI]: 1.12–1.58, p = 0.002). Additionally, multivariable MR analysis was performed to account for potential confounders, such as eosinophil count, smoking, and falls, which demonstrated that the association remains significant even after adjusting for these factors (OR = 1.29, 95% CI: 1.08–1.50, p = 0.004).

Conclusions:
This study provides robust evidence supporting the causal link between asthma and COPD, offering a more comprehensive understanding of their relationship.