Time-varying and dose-dependent effect of long-term statin use on risk of type 2 diabetes: a retrospective cohort study

Background We evaluated the effect of statin use on new-onset type 2 diabetes among individuals without atherosclerotic cardiovascular disease (ASCVD) using nationally representative South Korean claims data (2002-2013, N = 1,016,820). Methods A total of 13,698 patients (statin users 5273, non-statin users 5273) aged 40-74 years, newly diagnosed with dyslipidemia but without any history of diabetes or ASCVD, were selected in 2005. We followed up the final sample until 2013 and evaluated the cumulative incidence of type 2 diabetes. We used extended Cox regression models to estimate the time-varying adjusted hazard ratios of statin use on new-onset type 2 diabetes. We performed further analyses based on the cumulative defined daily dose of statin received per year to evaluate the degree of risk compared to non-statin users. Results Over the mean follow-up period of 7.1 years, 3034 patients developed type 2 diabetes; the number of statin users exceeded that of non-users, demonstrating that statin use significantly increased the risk of new-onset type 2 diabetes. The risk of new-onset type 2 diabetes differed among statin users according to cDDD per year (adjusted HR = 1.31 [95% CI 1.18-1.46] for less than 30 cDDD per year; 1.58 [1.43-1.75] for 30-120 cDDD per year; 1.83 [1.62-2.08] for 120-180 cDDD per year; and 2.83 [2.51-3.19] for more than 180 cDDD per year). The diabetogenic effect of pitavastatin was not statistically significant, but the risk was the largest for atorvastatin. Long-term exposure (>= 5 years) to statins was associated with a statistically significant increase in the risk of new onset type 2 diabetes in all statin subtypes explored, with the highest magnitude for simvastatin (HR = 1.916, 95% CI 1.647-2.228) followed by atorvastatin (HR = 1.830, 95% CI 1.487-2.252). Conclusions Statin use was significantly associated with an increased risk of new-onset type 2 diabetes. We also found a dose-response relationship in terms of statin use duration and dose maintenance. Periodic screening and monitoring for incident type 2 diabetes may be warranted in long-term statin users.