Systematic Review of the Effect of Adherence to Statin Treatment on Critical Cardiovascular Events and Mortality in Primary Prevention

Aim: Analyze the relative risks of critical cardiovascular outcomes and mortality associated with adherence to statin treatment in a clinical setting in people with no history of prior cardiovascular disease (CVD). Methods: A systematic review of the literature was conducted up to December 2016. The outcomes of interest were cardiovascular fatal or nonfatal events and all-cause mortality. Results: A total of 17 articles were included in a qualitative synthesis. Four were case-control nested in a retrospective cohort design and the other 11 were a cohort design. Seven studies compared the best adherer patients with the worst adherers. In the 3 studies (317 603 participants) that considered ischemic heart disease in this group, the pooled reduction in risk was 18% (95% confidence interval [CI]: 14%-22%, I-2 = 0%); for the CVD outcome, 2 studies (131 477 participants) showed a pooled reduction in risk of 47% (95% CI: 36%-56%, I-2 = 84.7%) with 1 included study showing a much larger reduction than the others; for the cerebrovascular event (CeVD) outcome, 2 studies (155 726 participants) showed a pooled reduction in risk of 26% (95% CI: 18%-34%, I-2 = 0%); and for mortality, the reduction in risk was 49% (95% CI: 39%-57%, I-2 = 62.4%). The other 4 studies (147 859 participants) compared the most adherent group with the rest. These showed a pooled risk reduction of CVD of 22% (95% CI: 6%-27%, I-2 = 0). Conclusion: Adherence to statins treatment is shown as a key element for primary prevention, although these are observational data and the risk of bias from confounding cannot be ruled out. Standardization of measures of adherence to treatment would improve comparability between studies. Further research is warranted to design effective interventions to improve patients' adherence.