Review Article

Association of Metformin Use with Asthma Exacerbation in Patients with Concurrent Asthma and Diabetes: A Systematic Review and Meta-Analysis of Observational Studies

Table 1

Characteristics of the two eligible studies and their participants.

First author (year)RegionDesignNumber of MU/MNUAge MU/MNUGender F(M) MU/MNUInclusion and exclusion criteriaFollow-upOutcomesStatistical methods

Li [11], 2016Taiwan Province, ChinaRetrospective cohort444/88864 (10.1)/64 (10.1)268 (176)/536 (352)Inclusion criteria: (1) aged ≥18 years with concurrent asthma and diabetes; (2) patients who have had at least one inpatient or two outpatient diagnoses of asthma and diabetes during the enrollment period; (3) patients who had at least one prescription for asthma and diabetes medication during the enrollment period; (4) matched patients’ date of the asthma and diabetes diagnosis must be earlier than the index date3 yearsAdjusted odds ratio of asthma hospitalization, emergency room visit, and exacerbationMultivariable logistic regression
Exclusion criteria: (1) patients who had a metformin prescription within 1 year before the index date; (2) patients if they had been diagnosed with COPD, any respiratory tract cancer, or bronchiectasis during the preindex period; (3) patients if they had an asthma-related hospitalization or emergency room visit during the preindex period; (4) patients with invalid or missing information of age, gender, diagnosis codes, medication prescriptions, and enrollment records
Wu [12], 201950 states of USARetrospective cohort11960/1196051.9 (9.3)/51.9 (9.9)7894 (4066)/7902 (4058)Inclusion criteria: (1) adult participants (age 18 or older) with both asthma and diabetes; (2) patients who had at least two compatible outpatient codes or one inpatient code during enrollment; (3) qualifying outpatient claims to be within one year6 yearsAdjusted odds ratio of asthma hospitalization, emergency room visit, exacerbation, and corticosteroid useCox proportional hazards model
Exclusion criteria: (1) individuals with any diagnosis of chronic obstructive pulmonary disease, bronchiectasis, or interstitial lung disease; (2) those with a contraindication for metformin use, type I diabetes, and a rheumatologic condition that may require systemic corticosteroids for symptoms unrelated to asthma

MU: metformin user; MNU: metformin nonuser.