Exploring the mechanisms and relationship between body mass index and asthma: findings from Mendelian randomization

The mechanism linking BMI and asthma remains unclear. Mendelian Randomization (MR) analysis was conducted using summary-level GWAS data from the FinnGen Biobank and the Open GWAS project. The analysis considering potential variables as mediators, including blood cell counts, blood pressure, and blood biomarkers. Three commonly used MR methods—the inverse-variance-weighted (IVW) method, weighted median (WM) method, and MR-Egger method—were employed to infer causal links. A two-step approach was used in mediation analysis to evaluate the causal links among BMI, candidate mediators, and asthma. Elevated BMI demonstrated a substantial correlation with increased asthma risk. Thirteen biomarkers mediated the relationship between BMI and asthma, mainly including leukocyte count (5.070%), apolipoprotein A levels (7.395%), cystatin C levels (5.345%), urate levels (9.057%), diastolic blood pressure (7.365%), and albumin levels (10.888%). These factors collectively explained over 50% of the increased asthma risk associated with BMI elevation. Additionally, eosinophil count and C-reactive protein were also identified as important mediators using the WM method. This study highlights the complex relationship between obesity, blood biomarkers, and asthma risk. Additional studies are required to validate these results and investigate causal relationships in various populations.