Metformin May Lower Exacerbation Risk in Patients With Both Asthma and Diabetes

The initiation of metformin therapy was associated with a lower risk for asthma exacerbations.

The initiation of metformin therapy was associated with a lower risk for asthma exacerbations, based on a lower hazard for asthma-related emergency department (ED) visits and hospitalizations, according to study results published in the Annals of the American Thoracic Society.

Investigators sought to determine whether treatment with metformin in a cohort of patients with diabetes and asthma is associated with a lower risk for the exacerbation of asthma. They conducted a 6-year, retrospective administrative claims-based cohort of patients with asthma and diabetes (age ≥18 years). To be eligible for the study, patients needed to be continuously enrolled for ≥1 calendar year and to participate in a health plan that submitted prescription claims during the study period. Individuals with a diagnosis of chronic obstructive pulmonary disease, bronchiectasis, or interstitial lung disease, as well as anyone with a contraindication for metformin, type 1 diabetes, or a rheumatologic disorder that might require the use of corticosteroids for symptoms unrelated to asthma were excluded from the study.

New users of metformin were matched with nonusers by propensity scores that were based on characteristics of medication use, demographics, and comorbidities. An exacerbation was defined as an asthma-related ED visit, hospitalization, or the filling of a systemic corticosteroid prescription within 14 days of an asthma-associated ambulatory visit. A total of 23,920 patients comprised the final propensity score-matched cohort. Overall, of all new users, 11,960 were matched successfully with nonusers. The mean patient age was 52 years; 66% were women, and 11% had experienced ≥1 asthma exacerbation in the past year.

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Over 27,577 person-years of follow-up, 3872 patients experienced an exacerbation of their asthma, for an overall incidence rate of 14.0 events per 100 person-years. The initiation of metformin was associated with a significantly lower hazard for asthma exacerbation (hazard ratio [HR], 0.92; 95% CI, 0.86-0.98; P <.01), which was linked to significantly lower hazards for asthma-related ED visits (HR, 0.81; 95% CI, 0.74-0.88; P <.01) and hospitalizations (HR, 0.67; 95% CI, 0.50-0.91; P <.01), but not with corticosteroid use (HR, 0.96; 95% CI, 0.90-1.03; P =.22). 

The investigators concluded that their findings suggest a possible benefit of metformin in more severe exacerbations of asthma. Additional studies are warranted, to explore the effects of metformin in well characterized patients with asthma, particularly in patients who are obese and exhibit metabolic dysfunction.


Wu TD, Keet CA, Fawzy A, Segal JB, Brigham EP, McCormack MC. Association of metformin initiation and risk of asthma exacerbation: a claims-based cohort study [published online August 15, 2019]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201812-897OC