Statin adherence and the risk of major coronary events in patients with diabetes: a nested case-control study

center dot Statin therapy is recommended in diabetes to lower the risk of coronary events. However, large randomized trials of statins performed specifically among diabetic patients have produced conflicting results. No long-term follow-up studies are available on the incidence of major coronary events and adherence to statin therapy in real-life patients with diabetes. WHAT THIS STUDY ADDS center dot The study results demonstrate that good adherence to statins is associated with a reduced risk of major coronary events in patients with diabetes, irrespective of the presence of coronary heart disease at statin initiation. This study provides further justification for maintenance statin therapy in diabetes. AIMS To evaluate whether good statin adherence is associated with a reduced incidence of major coronary events (MCEs) among diabetic patients with and without coronary heart disease (CHD). METHODS Using data derived by linkage of nationwide health databases in Finland, we conducted a nested case-control analysis of 3513 cases with an MCE, a composite of acute myocardial infarction and/or coronary revascularization, and 20 090 matched controls identified from a cohort of 60 677 statin initiators with diabetes. Cases and controls were matched according to gender, time of cohort entry and duration of follow-up and further classified to two risk groups according to the presence of CHD at statin initiation. The incidence of MCEs was compared between patients with good statin adherence (the proportion of days covered >= 80%) and patients with poor statin adherence (< 80%). Odds ratios (OR) for MCEs were estimated by conditional logistic regression adjusting for several covariables. RESULTS Good statin adherence was associated with a reduced incidence of MCEs in those with prior CHD [OR 0.84 (95% CI 0.74-0.95)] and in those without it [OR 0.86 (95% CI 0.78-0.95)]. The association persisted among those followed up for 5 years or longer [OR 0.77 (95% CI 0.58-1.02) and OR 0.79 (95% CI 0.66-0.94) respectively]. In sensitivity analyses, a reduced MCE incidence was observed also in those without any documented cardiovascular disease (CVD) at statin initiation [OR 0.87 (95% CI 0.78-0.96) overall and OR 0.80 (95% CI 0.66-0.97) for those followed up 5 years or longer]. CONCLUSIONS In patients with diabetes, good adherence to statins predicts reduced incidence of MCEs irrespective of the presence of CHD at statin initiation.