Metformin, a first-line diabetes medication, was associated with approximately 30% fewer asthma attacks in patients with both asthma and type 2 diabetes, according to research published in JAMA Internal Medicine.

The UK population-based cohort study analyzed data from more than 2 million adults with asthma. Among these, researchers identified 4,278 patients for a self-controlled case series and 8,424 patients for an inverse probability of treatment weighting cohort.

The study found that metformin use was linked to fewer asthma attacks in both analytical approaches (incidence rate ratio [IRR], 0.68). When glucagon-like peptide-1 receptor agonists (GLP-1RA) were added to metformin therapy, researchers observed an additional 40% reduction in asthma attacks (IRR, 0.60).

The data revealed that one in three adults with asthma had obesity, and nearly half of those individuals had type 2 diabetes. The association between metformin and reduced asthma attacks appeared independent of glycemic control, body mass index, blood eosinophil cell counts, and asthma severity.

Study limitations included the inability to assess medication adherence beyond prescription records and lack of information about metformin dosage due to missing data. The researchers could not examine changes in weight, though typical metformin-associated weight loss (2% to 5% per year) was unlikely to explain the observed association.

Conflict of interests can be found in the published study.