Efficacy of cholesterol-lowering therapy in 18 686 people with diabetes in 14 randomised trials of statins: a meta-analysis

Background: Although statin therapy reduces the risk of occlusive vascular events in people with diabetes mellitus, there is uncertainty about the effects on particular outcomes and whether such effects depend on the type of diabetes, lipid profile, or other factors. We undertook a prospective meta-analysis to help resolve these uncertainties. Methods: We analysed data from 18 686 individuals with diabetes (1466 with type 1 and 17 220 with type 2) in the context of a further 71 370 without diabetes in 14 randomised trials of statin therapy. Weighted estimates were obtained of effects on clinical outcomes per 1·0 mmol/L reduction in LDL cholesterol. Findings: During a mean follow-up of 4·3 years, there were 3247 major vascular events in people with diabetes. There was a 9% proportional reduction in all-cause mortality per mmol/L reduction in LDL cholesterol in participants with diabetes (rate ratio [RR] 0·91, 99% CI 0·82-1·01; p=0·02), which was similar to the 13% reduction in those without diabetes (0·87, 0·82-0·92; p<0·0001). This finding reflected a significant reduction in vascular mortality (0·87, 0·76-1·00; p=0·008) and no effect on non-vascular mortality (0·97, 0·82-1·16; p=0·7) in participants with diabetes. There was a significant 21% proportional reduction in major vascular events per mmol/L reduction in LDL cholesterol in people with diabetes (0·79, 0·72-0·86; p<0·0001), which was similar to the effect observed in those without diabetes (0·79, 0·76-0·82; p<0·0001). In diabetic participants there were reductions in myocardial infarction or coronary death (0·78, 0·69-0·87; p<0·0001), coronary revascularisation (0·75, 0·64-0·88; p<0·0001), and stroke (0·79, 0·67-0·93; p=0·0002). Among people with diabetes the proportional effects of statin therapy were similar irrespective of whether there was a prior history of vascular disease and irrespective of other baseline characteristics. After 5 years, 42 (95% CI 30-55) fewer people with diabetes had major vascular events per 1000 allocated statin therapy. Interpretation: Statin therapy should be considered for all diabetic individuals who are at sufficiently high risk of vascular events.