OBJECTIVES: To conduct a targeted literature review for the comparison of real-world prevalence of WHO-defined factors affecting adherence in asthma patients in Europe and the US

METHODS: We performed a targeted literature search on PubMed database (1999-2020) and Google Scholars search engine for English language publications on the factors affecting therapy adherence in asthma patients in Europe and the US. Only real-world, observational studies with PRO surveys or EMRs/EHRs/Online patient forum data collection methods were included. The factors were classified based on the 5 dimensions of adherence in the 2003 WHO report. The prevalence of adherence factors under each dimension were identified based on the number of studies and average of percentages (affected patients/total sample size) across studies. No statistical difference tests were conducted.

RESULTS: Six studies (n=2 inhaled therapies, n=3 oral and inhaled, n=1 unspecified) in Europe comprising 1,037 patients and six studies (n=5 inhaled therapies, n=1 unspecified) in the US comprising 1,833 patients were included in the literature review. The most prevalent factor in each dimension are as follows: 1.) Patient-related dimension: personal health and medication beliefs (Europe: n=4 studies, 40% patients; US: n=3 studies, 50% patients); 2.) Therapy-related: Adverse effect concerns (Europe: n=3 studies, 16% patients; US: n=2 studies, 18% patients); 3.) Condition-related: Reluctance to taking medication when asymptomatic (Europe: n=2 studies, 36% patients; US: n=2 studies, 45% patients). Socioeconomic-related and Healthcare system-related factors were not covered adequately by studies in both countries.

CONCLUSIONS: Findings from this literature review indicate that the prevalence of patient, therapy, and condition-related factors affecting asthma adherence in Europe are comparable to the US. The patients’ personal health and medication beliefs is the most prevalent factor impacting adherence in both Europe and the US.