Statin therapy and cardiovascular protection in type 2 diabetes: The role of baseline LDL-Cholesterol levels. A systematic review and meta-analysis of observational studies

Abstract

Aim: The guidelines recommend statins to prevent cardiovascular events in patients with type 2 diabetes (T2D) however, the importance of baseline LDL-Cholesterol (LDL-C) levels remains controversial. This study aimed to determine the association of statin use in T2D patients with major adverse cardiovascular events (MACE) and all-cause mortality and whether this association differs by baseline LDL-C levels. Data synthesis: Medline, Embase, and Web of Science were systematically searched from inception until January 2022. Observational studies in patients with T2D comparing statin users vs non-users, with reports of the baseline LDL-C levels, were included. Random-effects meta-analysis and meta-regression were performed to estimate the overall effect on the risk of all-cause mortality and MACE (a composite of myocardial infarction, heart failure, stroke, and revascularization events) and the modification in the association by baseline LDL-C levels. We categorized studies according to their baseline LDL-C levels into 1) <100 mg/dl (2.59 mmol/l), 2) 100–130 mg/dl (2.59–3.37 mmol/l) and 3) >130 mg/dl (3.37 mmol/l) categories. A total of 9 cohort studies (n = 403,411 individuals) fulfilled our criteria. The follow-up duration ranged from 1.7 to 8 years. The overall combined estimate showed that statin therapy was associated with a significantly lower risk of MACE (Hazard Ratio (HR): 0.70 [95% CI 0.59 to 0.83], Absolute risk reduction percentage (ARR%): 3.19% [95%CI 0.88 to 5.50%) and all-cause mortality (HR: 0.60 [95% CI 0.46 to 0.79], ARR%: 5.23% [95% CI 2.18 to 8.28%), but varied, albeit not statistically significant, by baseline LDL-C levels. Studies with baseline LDL-C levels higher than 130 mg/dl had the greatest reduction of MACE (HR: 0.58 [95% CI 0.37 to 0.90]) and all-cause mortality risk (HR: 0.51 [95% CI [ 0.29 to 0.90]). The HRs of MACE in studies with LDL-C levels of 100–130 mg/dl and <100 mg/dl categories were respectively (0.70 [95% CI 0.59 to 0.83]) and (0.83 [95% CI [0.68 to 1.00]); and that of all-cause mortality were respectively (0.62 [95% CI 0.38 to 1.01]) and (0.67 [95% CI [0.44 to 1.02]). Statin use changes the HRs of MACE (0.99 [95%CI, 0.98 to 0.99]; P = 0.04) and all-cause mortality (0.99 [95% CI 0.98 to 1.01]; P = 0.8) per each mg/dl increase in baseline LDL-C level in meta-regression analyses. Conclusion: Statin therapy in patients with T2D was associated with reduced risk of MACE and all-cause mortality. Significant differences across studies with different baseline LDL-C levels were not observed.