Am Fam Physician. 2008 Nov 15;78(10) Online.
Background: More than 170 million persons worldwide are estimated to have diabetes. This number is increasing rapidly. Studies have estimated the absolute risk of coronary mortality to be three to five times higher in persons with diabetes than in those without this disease. The risk of atherosclerotic vascular disease is believed to be similarly increased. Although the underlying type of dyslipidemia differs between type 1 and type 2 diabetes, both types are believed to benefit from lipid-lowering therapy. The Cholesterol Treatment Trialists’ (CTT) Collaboration considered data from 14 major randomized clinical trials to clarify the benefits of statin therapy for persons with diabetes.
The Study: The CTT collaborators conducted a meta-analysis of lipid-lowering studies that aimed to treat at least 1,000 participants for two years or longer. Studies were included if no other differences in modification of other risk factors between treatment groups were intended. The primary outcome was the number of clinical events per 1.0 mmol per L (38.7 mg per dL) reduction of low-density lipoprotein (LDL) cholesterol from baseline. Data were available on 18,686 persons diagnosed with diabetes before admission to the study, and on 71,370 other persons not known to have diabetes.
Results: Most participants with diabetes had type 2 diabetes (17,220 persons with type 2 and 1,466 persons with type 1). A total of 3,247 major vascular events were documented in participants with diabetes during an average follow-up of 4.3 years. The reduction in vascular events was 21 percent for each 1.0 mmol per L decrease in LDL cholesterol for participants with and without diabetes. For each mmol per L decrease in LDL cholesterol level, participants with diabetes achieved a 9 percent reduction in all-cause mortality, a 12 percent decrease in coronary artery mortality, and a 13 percent reduction in all-vascular mortality. These reductions were similar to those achieved by participants without diabetes. Participants with diabetes also achieved significant reductions in major coronary events, coronary revascularization, and stroke. In subgroup analysis, the reductions in vascular events were similar between participants with diabetes who had vascular disease or hypertension, and those who did not have these conditions at the beginning of trials. The reductions in vascular events were also similar in patients with different types of dyslipidemias.
Conclusion: The authors calculate that statin therapy was associated with a 10 percent reduction in major vascular events in the first year, and a 20 to 30 percent reduction in subsequent years of therapy. Among participants with diabetes, 42 fewer persons per 1,000 had major vascular events after five years. The authors also predict that statin therapy for major vascular events in patients with diabetes will be as cost-effective as in patients without diabetes.
Cholesterol Treatment Trialists’ (CTT) Collaborators. Efficacy of cholesterol-lowering therapy in 18,686 people with diabetes in 14 randomised trials of statins: a meta-analysis. Lancet. January 12, 2008;371:117-125.
Copyright © 2008 by the American Academy of Family Physicians.
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