Purpose: Cardiovascular complications account for over 50% of mortality among patients with type 2 diabetes mellitus. We quantify the cardiovascular benefit of lowering cholesterol, blood pressure, and glucose levels in these patients.
Methods: We conducted a meta-analysis of randomized controlled trials in type 2 diabetes or diabetes subgroups, comparing the cardiovascular effects of intensive medication control of risk factor levels in standard therapy or placebo. We identified trials by searching MEDLINE (1966 to 2000) and review articles. Treatment details, patient characteristics, and outcome events were obtained using a specified protocol. Data were pooled using fixed-effects models.
Results: Seven serum cholesterol-lowering trials, six blood pressure-lowering trials, and five blood glucose-lowering trials met eligibility criteria. For aggregate cardiac events (coronary heart disease death and nonfatal myocardial infarction), cholesterol lowering [rate ratio (RR) = 0.75; 95% confidence interval (CI): 0.61 to 0.93) and blood pressure lowering (RR = 0.73; 95% CI: 0.57 to 0.94) produced large, significant effects, whereas intensive glucose lowering reduced events without reaching statistical significance (RR = 0.87; 95% CI: 0.74 to 1.01). We observed this pattern for all individual cardiovascular outcomes. For cholesterol-lowering and blood pressure-lowering therapy, 69 to 300 person-years of treatment were needed to prevent one cardiovascular event.
Conclusion: The evidence from these clinical trials demonstrates that lipid and blood pressure lowering in patients with type 2 diabetes is associated with substantial cardiovascular benefits. Intensive glucose lowering is essential for the prevention of microvascular disease, but improvements in cholesterol and blood pressure levels are central to reducing cardiovascular disease in these patients.