Identifying comorbidities associated with switching patterns of real-world asthma treatment: a drug utilization study

Comorbidities can aggravate asthma, influencing treatment needed to control symptoms or leading to under- or overtreatment when causing asthma-like symptoms. Little is known about how comorbidities affect asthma treatment trajectories in clinical practice. This study aims to predict subgroup differences within switching patterns of inhaled asthma medication. This retrospective inception cohort study uses the IADB.nl community pharmacy dispensing database. Included were 16- to 45-year-olds, who initiated inhaled asthma medication between 1994-2021 in the Netherlands. The parametric g-formula predicted the associations of age, sex, arthritis, atopic diseases, cardiovascular diseases, diabetes, use of immunosuppressants, mental health problems, gastroesophageal reflux disease, and thyroid disease, separately, with switching patterns of GINA treatment steps, within two years after initiation. 45-year-olds switched on average earlier and more often than 16-year-olds (8.7 vs. 9.0 months, p=0.04; 2.3 vs. 2.1 times, p<0.01). Fewer individuals switched in presence compared to absence of atopic diseases or mental health problems (both 66 vs 68%, p=<0.01), and if they switched, after longer treatment duration (both 9.0 vs. 8.8 months, p=0.03 and p=0.04, respectively). In presence compared to absence of gastroesophageal reflux disease, individuals switched later (9.1 vs. 8.8 months; p<0.01). For other subgroups, no evidence was found for differences in switching patterns. Even though comorbidities can significantly impact the burden of asthma, their individual impact on differential treatment switching patterns after initiation seems limited.