Evaluating different low-density lipoprotein cholesterol thresholds to initiate statin for prevention of cardiovascular diseases in patients with type 2 diabetes mellitus: A target trial emulation study

Aim: The present study aimed to evaluate the effect of statin therapy for primary prevention of cardiovascular diseases (CVDs) when initiating therapy at different baseline low-density lipoprotein cholesterol (LDL-C) levels in patients with type 2 diabetes mellitus (T2DM). Materials and Methods: Using territory-wide public electronic medical records in Hong Kong, we emulated a sequence of trials on patients with T2DM with elevated LDL-C levels in every calendar month from January 2008 to December 2014. Pooled logistic regression was applied to obtain the hazard ratios for the major CVDs (stroke, myocardial infarction, heart failure), all-cause mortality and major adverse events (myopathies and liver dysfunction) of statin therapy. Results: The estimated hazard ratios (95% confidence intervals) of CVD incidence for statin initiation were 0.78 (0.72, 0.84) in patients with baseline LDL-C of 1.8-2.5 mmol/L (i.e., 70-99 mg/dL) and 0.90 (0.88, 0.92) in patients with baseline LDL-C >= 2.6 mmol/L (i.e., >= 100 mg/dL) in intention-to-treat analysis, which was 0.59 (0.51, 0.68) and 0.77 (0.74, 0.81) in per-protocol analysis, respectively. No significant increased risks were observed for the major adverse events. The absolute 10-year risk difference of overall CVD in per-protocol analysis was -7.1% (-10.7%, -3.6%) and -3.9% (-5.1%, -2.7%) in patients with baseline LDL-C 1.8-2.5 and >= 2.6 mmol/L, respectively. The effectiveness and safety were consistently observed in patients aged >75 years initiating statin at both LDL-C thresholds. Conclusions: Compared with the threshold of 2.6 mmol/L, initiating statin in patients with a lower baseline LDL-C level at 1.8-2.5 mmol/L can further reduce the risks of CVD and all-cause mortality without significantly increasing the risk of major adverse events in patients with T2DM, including patients aged >75 years.