Adherence to chronic medication in older populations: application of a common protocol among three European cohorts

Purpose The purpose of this study was to evaluate and compare medication adherence to chronic therapies in older populations across different regions in Europe. Methods This explorative study applied a harmonized method of data extraction and analysis from pharmacy claims databases of three European countries to compare medication adherence at a cross-country level. Data were obtained for the period between January 1, 2010, and December 31, 2011. Patients (aged ≥65 years) who newly initiated to oral antidiabetics, antihyperlipidemics, or antiosteoporotics were identified and followed for over a 12-month period. Main outcome measures were medication adherence (medication possession ratio, [MPR]; implementation) and persistence on index treatment. All country-specific data sets were prepared by employing a common data input model. Outcome measures were calculated for each country and pooled using random effect models. Results In total, 39,186 new users were analyzed. In pooled data from the three countries, suboptimal implementation (MPR <80%) was 52.45% (95% CI: 33.43–70.79) for antihy-perlipidemics, 61.35% (95% CI: 52.83–69.22) for antiosteoporotics, and 30.33% (95% CI: 25.53–35.60) for oral antidiabetics. Similarly, rates of non-persistence (discontinuation) were 55.63% (95% CI: 35.24–74.29) for antihyperlipidemics, 60.24% (95% CI: 45.35–73.46) for antiosteoporotics, and 46.80% (95% CI: 36.40–57.4) for oral antidiabetics. Conclusion Medication adherence was suboptimal with >50% of older people non-adherent to antihyperlipidemics and antiosteoporotics in the three European cohorts. However, the degree of variability in adherence rates among the three countries was high. A harmonized method of data extraction and analysis across health-related database in Europe is useful to compare medication-taking behavior at a cross-country level.