Adherence to statins and its impact on clinical outcomes: a retrospective population-based study in China

BACKGROUND: While the benefit of adherence to statins on clinical outcomes has been proved, this benefit may be heterogeneous among patients who initiated statins for primary or secondary prevention purpose. This study aimed to investigate the impact of statin adherence on clinical outcomes among patients who initiated statins for primary and secondary prevention in China. METHODS: Adult patients in Tianjin Urban Employee Basic Medical Insurance database who initiated ≥2 prescriptions of statins from 2012 through 2013 were included and grouped into primary and secondary prevention subgroups according to their cardiovascular diseases (CVD) history during the prior 12-month baseline period. Proportion of days covered (PDC) was used to measure statin adherence in the initial 12-month follow-up. Clinical outcomes were measured by the incidence of major adverse cardiovascular events (MACE) during the 13th–24th months follow-up, and were compared between the patients with PDC ≥ 0.5 and patients with PDC < 0.5 using Cox regression models in primary and secondary prevention subgroups. Sensitivity analyses were conducted in propensity score matched groups. RESULTS: 99,655 patients were finally included. The mean (SD) PDC was 0.19 (0.15) in primary prevention subgroup (N = 34,372), with 5.4% patients had PDC ≥ 0.5. The patients with PDC ≥ 0.5 had a 37% reduced risk of MACE compared with patients with PDC < 0.5 (Unadjusted incidence rate of MACE: 1.1% vs. 1.4%; all-adjusted HR = 0.63; 95% CI, 0.41–0.98). While, no significant difference was observed in the secondary prevention subgroup (N = 65,283) between patients with PDC ≥ 0.5 and patients with PDC < 0.5 (Unadjusted incidence rate of MACE: 4.6% vs. 2.8%; all-adjusted HR = 1.08, 95% CI, 0.92–1.28). These findings were confirmed by the sensitivity analyses in propensity score matched groups. CONCLUSIONS: Statin adherence was very poor in China, and statin adherence is associated with decreased risk of MACE in patients for primary prevention, while further exploration is needed for secondary prevention.