Real-world evaluation of the impact of statin intensity on adherence, persistence and discontinuing of statin therapy: evidence from the Scottish population

Background: Recent treatment guidelines recommend high intensity statins for secondary prevention; however, the impact on patients’ medication taking behaviour is unknown. This study aimed to address this using Scottish datasets.
Methods: Retrospective cohort study, using the Scottish linked electronic health records, comprising adult patients (≥ 18 years) newly initiating statins between Jan/2010 and Dec/2015. Study outcomes were adherence, discontinuation, and persistence to treatment, stratified by three exposure groups (high, moderate, and low intensity) based on the level of cholesterol reduction. Discontinuation and persistence were calculated using the refill-gap and the anniversary methods (admissible gap 60 days). Proportion of Days Covered was used as a proxy for adherence. Kaplan-Meier survival curves and Cox Proportional Hazard models were used to evaluate discontinuation. Associations between adherence, persistence and statin intensity were assessed using logistic regression models; analyses were adjusted for the main confounders.
Results: 73,716 patients with a mean age of 61.4±12.6 years were included; the majority (88.3%) initiated on moderate intensity statins. Discontinuation rates differed significantly between intensity levels, with high intensity patients 57% less likely to discontinue treatment compared to moderate intensity (HR 0.43 [95% CI 0.34 – 0.55]; no prior CVD: 0.80 [0.74 – 0.86]). Persistence declined over time. High intensity patients had the highest persistence rates at all analysed time points. Overall adherence was 52.6%; higher among high-intensity (63.7%).
Conclusions: Interestingly, high intensity statins was associated with better persistence and adherence to therapy; however, overall long-term persistence and adherence to statins therapy remain a challenge, particularly among patients without prior CVD