Real-world evaluation of the impact of statin intensity on adherence and persistence to therapy : a Scottish population-based study

Aim: To assess associations between statin intensity and adherence, persistence and discontinuation of statin therapy in Scotland. Method: Retrospective cohort study, using linked electronic health records covering a period from January 2009 to December 2016. The study cohort included adult patients (≥18 years) newly initiating statins within Greater Glasgow and Clyde, Scotland. Study outcomes comprised adherence, discontinuation and persistence to treatment, stratified by three exposure groups (high, moderate and low intensity). Discontinuation and persistence were calculated using the refill-gap and anniversary methods, respectively. Proportion of days covered (PDC) was used as a proxy for adherence. Kaplan-Meier survival curves and Cox proportional hazard models were used to evaluate discontinuation, and associations between adherence/persistence and statin intensity were assessed using logistic regression. Results: A total of 73 716 patients with a mean age of 61.4 ± 12.6 years were included; the majority (88.3%) received moderate intensity statins. Discontinuation rates differed between intensity levels, with high-intensity patients less likely to discontinue treatment compared to those on moderate intensity (prior cardiovascular disease [CVD]: HR 0.43 [95% CI 0.34-0.55]; no prior CVD: 0.80 [0.74-0.86]). Persistence declined over time, and high-intensity patients had the highest persistence rates. Overall, 52.6% of patients were adherent to treatment (PDC ≥ 80%), but adherence was considerably higher among high-intensity patients (63.7%). Conclusion: High-intensity statins were associated with better persistence and adherence to treatment, but overall long-term persistence and adherence remain a challenge, particularly among patients without prior CVD. This needs addressing