Metformin effects on respiratory and metabolic outcomes in asthma and metabolic syndrome: a double-blind, randomized, placebo-controlled clinical trial

Introduction: Metabolic syndrome (MetS) could be associated with worsened asthma control and more severe and frequent asthma attacks. Metformin has been suggested as a potential treatment for MetS, which could decrease airway reactivity and lead to improved asthma control and reduced emergency department (ED) visits. However, the existing data have predominantly focused on diabetic patients only. Thus, in the present study, we aimed to investigate the effects of metformin in patients with concurrent asthma and MetS. Methods: This trial was conducted on two groups of patients (55 in each group) with concurrent asthma and MetS, each receiving either metformin hydrochloride or an identical placebo. Patients were followed up after 3 months and assessed regarding clinical outcomes, asthma control tests (ACTs), pulmonary function test parameters, C-reactive protein (CRP) levels, frequency of asthma attacks, ED visits, and hospitalization rate. Results: The metformin group showed statistically significant improvements in indices regarding ACT score, O 2 saturation, anthropometric indices, blood sugar control, CRP, and lipid profile compared to the placebo group (all P < 0.05). Additionally, the metformin group showed significantly higher forced expiratory volume in 1 s (FEV 1 ) ( P = 0.014, and effect size = 5.6%) and forced vital capacity (FVC) ( P = 0.001, and effect size = 9.2%) in the multivariate analysis after controlling for the confounding effects of baseline parameters and sex. Although the metformin group demonstrated a trend toward a reduction in severe asthma attacks, ED visits, or hospitalization rates, the effects were not statistically significant ( P > 0.05). Conclusion: Our findings demonstrate that metformin administration in patients with concurrent asthma and MetS could lead to substantial enhancements in ACT score, FEV 1 , and FVC.