Effects of the occurrence of a first cardiovascular event on statin adherence in type 2 diabetes: A matched cohort design

Objectives: Adherence to statin therapy is important for an effective reduction in cardiovascular events. We aimed to assess the effect of the occurrence of a first cardiovascular event on adherence rates in type 2 diabetes patients using a matched cohort design. Methods: A matched cohort study was performed within the IADB. nl pharmacy database among type 2 diabetes patients, who initiated statin treatment for primary prevention. Index patients experienced a first event (index date) after initiation whereas reference patients did not. Index and reference patients were matched on gender, age at statin initiation, statin initiation date, adherence level before the index date and follow-up period. Adherence was measured as percentages of days covered and classified into: non-adherent, partial-adherent or full-adherent. Adherence rates were measured from statin initiation until the index date, and from the index date until end of follow-up, for reference patients in both cases the same follow-up period was used. Mean adherence rates between index and reference before and after were compared by the use of an independent samples T-test. Results: From the 855 index patients 375 could be matched to a reference patient. Mean adherence rates before the index date were 79% for both groups. After the index date, mean adherence rates were 81% for index patients and 71% for reference patients (p-value