Aims: To evaluate statin non-persistence and non-adherence as discrete processes in diabetes patients, and identify pharmacy-based predictors of these processes in the first year after statin initiation.
Methods: We conducted a retrospective cohort study of statin initiators using a pharmacy database. Persistence and adherence were measured in the first, second and third year. Non-persistence was defined as a gap >180 days. Non-adherence was calculated in persistent patients and defined as a medication possession ratio <80%. Cox regression hazard ratios (HRs) and logistic regression odds ratios (ORs) were assessed for sociodemographic and medication-related factors as possible predictors.
Results: Of 12,741 initiators, 20.0% were non-persistent in the first year, while 9.0% and 7.5% were non-persistent in the second and third years. Non-adherence in persistent patients increased from 13.4% in the first to 15.6% and 18.1% in the second and third years. Predictors of non-persistence were female gender (HR: 1.10; 95% CI: 1.01-1.19), older age (HR: 1.52; 95% CI: 1.31-1.75), primary prevention (HR: 1.10; 95% CI: 1.00-1.20), initiating on low dose (HR: 1.44; 95% CI: 1.07-1.94) or standard dose (HR: 1.56; 95% CI: 1.16-2.10), and no cardiovascular co-medication (HR: 1.19; 95% CI: 1.07-1.33), while patients with four or more other medications were more likely to be persistent. Age <50 years (OR: 1.47; 95% CI: 1.22-1.77), low socioeconomic status (OR: 1.27; 95% CI: 1.12-1.45) and primary prevention (OR: 1.21; 95% CI: 1.07-1.38) were predictors of non-adherence, while females were more likely to be adherent (OR: 0.87; 95% CI: 0.77-0.98).
Conclusion: Non-persistence was the foremost problem in the first year after statin initiation, while non-adherence in persistent patients increased in the second and third years. Pharmacy-based predictors of statin non-persistence were different from predictors of non-adherence among persistent patients.
Keywords: Medication adherence; diabetes mellitus; hydroxymethylglutaryl-CoA reductase inhibitors.