Statins and the risk of diabetes: evidence from a large population-based cohort study.

OBJECTIVE To investigate the relationship between adherence with statin therapy and the risk of developing diabetes. RESEARCH DESIGN AND METHODS The cohort comprised 115,709 residents of the Italian Lombardy region who were newly treated with statins during 2003 and 2004. Patients were followed from the index prescription until 2010. During this period, patients who began therapy with an antidiabetic agent or were hospitalized for a main diagnosis of type 2 diabetes were identified (outcome). Adherence was measured by the proportion of days covered (PDC) with statins (exposure). A proportional hazards model was fitted to estimate hazard ratios (HRs) and 95% CIs for the exposure-outcome association, after adjusting for several covariates. A set of sensitivity analyses was performed to account for sources of systematic uncertainty. RESULTS During follow-up, 11,154 cohort members experienced the outcome. Compared with patients with very-low adherence (PDC <25%), those with low (26-50%), intermediate (51-75%), and high (>= 75%) adherence to statin therapy had HRs (95% CIs) of 1.12 (1.06-1.18), 1.22 (1.14-1.27), and 1.32 (1.26-1.39), respectively. CONCLUSIONS In a real-world setting, the risk of new-onset diabetes rises as adherence with statin therapy increases. Benefits of statins in reducing cardiovascular events clearly overwhelm the diabetes risk.