Acute kidney injury in statin initiators.

PURPOSE: Statins are widely used for preventing cardiovascular disease, yet recent reports suggest an increased risk of acute kidney injury (AKI). We estimated the one-year risk of AKI associated with statin initiation and determined the comparative safety of individual statin formulations.
METHODS: We performed a cohort study in insurance billing data from commercial and Medicare insurance plans in the United States for the years 2000-2010. We identified statin initiators and non-users with histories of medication use and healthcare utilization. AKI diagnosis codes were identified in the one year following the index date. We estimated hazard ratios (HR) and 95% confidence intervals (CI) with adjusted and propensity score (PS)-matched Cox-proportional hazards models. Models were run separately in insurance groups and adjusted for cardiovascular and renal risk factors, markers of healthcare utilization, and other medication use.
RESULTS: We identified 3,905,155 statin initiators and 2,817,621 eligible non-users. The adjusted HR of AKI in statin initiators compared to non-users was: commercial, HR = 1.04 (95% CI: 0.99, 1.09); Medicare, HR = 0.72 (95% CI: 0.70, 0.75). PS-matching yielded: commercial, HR = 0.82 (95% CI: 0.78, 0.87); Medicare, HR = 0.66 (95% CI: 0.63, 0.69). As individual formulations, higher-potency simvastatin was associated with an increased risk of AKI over lower-potency simvastatin in adjusted models: commercial, HR = 1.42 (95% CI: 1.28, 1.58); Medicare, HR = 1.24 (95% CI: 1.15, 1.35).
CONCLUSIONS: As a class, statin initiation was not associated with an increase in AKI. However, higher-potency simvastatin did exhibit an increased AKI risk.