Asthma
Aiya Almogaber, PharmD
A recent study published in the January 2025 issue of JAMA Internal Medicine suggested that metformin, widely used to manage T2D, may also lower the risk of asthma exacerbations. Researchers analyzed data from thousands of patients with both conditions, uncovering an intriguing link that could have implications for asthma management.
Asthma and T2D are common chronic conditions that often coexist, particularly among individuals with obesity. Previous research has suggested a connection between metabolic dysfunction and poor asthma control, but the role of antidiabetic medications in asthma management remains unclear.
According to study author Chloe Bloom, BSc, MSc, PhD, many patients with asthma also have T2D, raising questions about whether medications used to regulate blood glucose could also influence asthma outcomes. In a recent population-based study, Bloom and colleagues explored whether metformin—an affordable, first-line treatment for T2D—could play a role in reducing asthma exacerbations. Their findings suggested a potential dual benefit, sparking interest in whether this widely used medication could be repurposed to help patients with both conditions.
The link between T2D and asthma
Obesity and T2D are common among adults with asthma and have been associated with an increased risk of asthma attacks. In a large population-based cohort, more than half of adults with asthma were overweight or obese, and nearly 7% had a T2D diagnosis. Despite this overlap, glycemic control is often overlooked in asthma patients. The authors noted that a majority of those with elevated A1C levels remained undiagnosed or untreated for diabetes.
Metformin’s effects extend beyond glucose control. Previous findings suggest metformin may reduce airway inflammation and hyperresponsiveness, potentially influencing asthma outcomes. However, epidemiological evidence on the association between metformin use and asthma attacks has been limited. To address this gap, researchers analyzed data from more than 12,000 patients with asthma and diabetes to assess whether metformin or other antidiabetic medications influence asthma exacerbations.
Study design and methods
Researchers conducted a population-based cohort study using data from the U.K. Clinical Practice Research Datalink Aurum, spanning from 2004 to 2020. To strengthen the reliability of their findings, they employed two complementary approaches: a self-controlled case series (SCCS) and an inverse probability of treatment weighting (IPTW) cohort study.
The SCCS approach included 4,278 patients with asthma and T2D who were new users of metformin. This design allowed each patient to serve as their own control, minimizing confounding factors. The IPTW cohort included 8,424 patients and compared asthma exacerbation rates between metformin users and nonusers while adjusting for potential confounders such as age, BMI, and glycemic control.
The primary outcome was the first asthma exacerbation within 12 months of follow up, defined as a short course of oral corticosteroids, an asthma-related emergency visit, hospital admission, or death. Researchers also assessed whether metabolic markers, including A1C levels, BMI, and blood eosinophil counts, modified the association between metformin use and asthma attacks.
Study results
Among the 12,702 patients included in the analysis, metformin use was associated with a lower risk of asthma exacerbations across both study approaches. In the SCCS analysis, metformin users experienced a 32% reduction in asthma attacks compared to the pre-exposure period. Similarly, in the IPTW cohort, metformin use was linked to a 24% lower risk of asthma attacks compared with nonusers.
The protective effect of metformin was greater than expected, Bloom noted, with reductions observed across various patient subgroups regardless of glycemic control, BMI, blood eosinophil counts, or asthma severity. Notably, GLP-1 receptor agonists provided an additional benefit, further lowering asthma attack risk by about 40%. These findings suggest that the impact of metformin and GLP-1s on asthma outcomes may extend beyond their effects on blood glucose regulation.
Negative control analyses, which examined unrelated conditions such as abdominal pain and fractures, found no significant associations, supporting the validity of the observed findings.
Future directions
Bloom said that metformin’s affordability, widespread availability, and ease of use make it an attractive option for patients, especially if future research continues to support its benefits.
Despite the promising results, the authors emphasized the need for further investigation to confirm these findings and provide definitive guidance for clinical practice. ■