Am Fam Physician. 2008;78(10):online-only-
Background: More than 170 million personsworldwide are estimated to have diabetes.This number is increasing rapidly. Studieshave estimated the absolute risk of coronarymortality to be three to five times higher inpersons with diabetes than in those withoutthis disease. The risk of atheroscleroticvascular disease is believed to be similarlyincreased. Although the underlying type ofdyslipidemia differs between type 1 and type2 diabetes, both types are believed to benefitfrom lipid-lowering therapy. The CholesterolTreatment Trialists’ (CTT) Collaborationconsidered data from 14 major randomizedclinical trials to clarify the benefits of statintherapy for persons with diabetes.
The Study: The CTT collaborators conducteda meta-analysis of lipid-lowering studies thataimed to treat at least 1,000 participants fortwo years or longer. Studies were included ifno other differences in modification of otherrisk factors between treatment groups wereintended. The primary outcome was thenumber of clinical events per 1.0 mmol per L(38.7 mg per dL) reduction of low-densitylipoprotein (LDL) cholesterol from baseline.Data were available on 18,686 personsdiagnosed with diabetes before admission tothe study, and on 71,370 other persons notknown to have diabetes.
Results: Most participants with diabetes hadtype 2 diabetes (17,220 persons with type 2and 1,466 persons with type 1). A totalof 3,247 major vascular events were documentedin participants with diabetes duringan average follow-up of 4.3 years. The reductionin vascular events was 21 percent foreach 1.0 mmol per L decrease in LDL cholesterolfor participants with and without diabetes.For each mmol per L decrease in LDLcholesterol level, participants with diabetesachieved a 9 percent reduction in all-causemortality, a 12 percent decrease in coronaryartery mortality, and a 13 percent reductionin all-vascular mortality. These reductionswere similar to those achieved by participantswithout diabetes. Participants with diabetesalso achieved significant reductions in majorcoronary events, coronary revascularization, and stroke. In subgroup analysis, the reductionsin vascular events were similar betweenparticipants with diabetes who had vasculardisease or hypertension, and those who didnot have these conditions at the beginning oftrials. The reductions in vascular events werealso similar in patients with different types ofdyslipidemias.
Conclusion: The authors calculate that statintherapy was associated with a 10 percentreduction in major vascular events in the firstyear, and a 20 to 30 percent reduction in subsequentyears of therapy. Among participantswith diabetes, 42 fewer persons per 1,000had major vascular events after five years.The authors also predict that statin therapyfor major vascular events in patients withdiabetes will be as cost-effective as in patientswithout diabetes.