Low-Dose Aspirin for Primary Prevention of Cardiovascular Events in Patients With Diabetes: A Meta-Analysis

Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, 73104, USA.
The American Journal of the Medical Sciences (Impact Factor: 1.39). 01/2011; 341(1):1-9. DOI: 10.1097/MAJ.0b013e3181f1fba8
Source: PubMed


The use of low-dose aspirin for primary prevention of cardiovascular events in patients with diabetes is recommended by existing guidelines, but definitive evidence supporting its efficacy is lacking. The authors undertook a meta-analysis of published trials to determine the effect of low-dose aspirin for primary prevention of cardiovascular events in patients with diabetes.
Randomized controlled trials comparing low-dose aspirin versus placebo or no treatment in patients with diabetes (either exclusively or as a subgroup) with no previous history of cardiovascular disease were identified through MEDLINE and EMBASE databases.
Seven randomized controlled trials met the inclusion criteria. Two studies included exclusively patients with diabetes, whereas the remaining 5 studies included patients with diabetes as a subgroup. Two studies were excluded because they did not provide diabetes-specific data. Overall, aspirin was associated with a nonsignificant reduction in the hazard rate of the composite endpoint of major cardiovascular events compared with control (hazard ratio = 0.89, 95% confidence interval: 0.70-1.13, P = 0.33). Similarly, there was a nonsignificant reduction in the hazard rate of the individual endpoints of myocardial infarction, stroke, cardiovascular and all-cause mortality. The risk of major bleeding increased nonsignificantly with aspirin compared with control (relative risk = 3.02, 95% confidence interval: 0.48-18.86, P = 0.24).
The role of low-dose aspirin for primary prevention of cardiovascular events in patients with diabetes remains unproven, and its routine use cannot be justified at present. More trials are needed to definitively address this issue.

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    • "Composite primary outcomes in the primary prevention of CVD in diabetes show that for all seven of the included systematic reviews and meta-analyses, all upper 95% confidence intervals included the possibility of no improvement, and for some, confidence intervals clearly implied the possibility of a greater risk from aspirin [30,31,32]. "
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    ABSTRACT: Aspirin has been recommended for primary prevention of cardiovascular disease (CVD) and cancer, but overall benefits are unclear. We aimed to use novel methods to re-evaluate the balance of benefits and harms of aspirin using evidence from randomised controlled trials, systematic reviews and meta-analyses. Data sources included ten electronic bibliographic databases, contact with experts, and scrutiny of reference lists of included studies. Searches were undertaken in September 2012 and restricted to publications since 2008. Of 2,572 potentially relevant papers 27 met the inclusion criteria. Meta-analysis of control arms to estimate event rates, modelling of all-cause mortality and L'Abbé plots to estimate heterogeneity were undertaken. Absolute benefits and harms were low: 60-84 major CVD events and 34-36 colorectal cancer deaths per 100,000 person-years were averted, whereas 46-49 major bleeds and 68-117 gastrointestinal bleeds were incurred. Reductions in all-cause mortality were minor and uncertain (Hazard Ratio 0.96; 95% CI: 0.90-1.02 at 20 years, Relative Risk [RR] 0.94, 95% CI: 0.88-1.00 at 8 years); there was a non-significant change in total CVD (RR 0.85, 95% CI: 0.69-1.06) and change in total cancer mortality ranged from 0.76 (95% CI: 0.66-0.88) to 0.93 (95% CI: 0.84-1.03) depending on follow-up time and studies included. Risks were increased by 37% for gastrointestinal bleeds (RR 1.37, 95% CI: 1.15-1.62), 54%-66% for major bleeds (Rate Ratio from IPD analysis 1.54, 95% CI: 1.30-1.82, and RR 1.62, 95% CI: 1.31-2.00), and 32%-38% for haemorrhagic stroke (Rate Ratio from IPD analysis 1.32; 95% CI: 1.00-1.74; RR 1.38; 95% CI: 1.01-1.82). Findings indicate small absolute effects of aspirin relative to the burden of these diseases. When aspirin is used for primary prevention of CVD the absolute harms exceed the benefits. Estimates of cancer benefit rely on selective retrospective re-analysis of RCTs and more information is needed.
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    ABSTRACT: Reduction of cardiovascular disease (CVD) events in patients with type 2 diabetes remains an area of intense interest and research. Recent trials of lower systolic blood pressure goals and combination lipid therapy have failed to show a significant reduction in CVD events in patients with diabetes. Antiplatelet agents are an additional option for CVD risk reduction in patients both with and without diabetes. However, two recent trials have questioned the role of aspirin in the primary prevention of CVD events in patients with diabetes. Although sub-analyses of larger trials have suggested a potential benefit of thienopyridine therapy in patients with diabetes, direct comparative trials are lacking and aspirin remains the appropriate first-line agent. Recent guidelines issued by the American Diabetes Association, American Heart Association, and American College of Cardiology Foundation on the use of aspirin for primary prevention in patients with diabetes remain the standard of practice. Two ongoing trials will help to address the question of the relative benefit of aspirin in patients with diabetes. The Aspirin and Simvastatin Combination for Cardiovascular Events Prevention Trial in Diabetes (ACCEPT-D) and A Study of Cardiovascular Events in Diabetes (ASCEND) are both randomized trials of 100 mg of aspirin compared to placebo and will enroll a combined 15,000 patients with diabetes between the two trials. Results may become available as soon as 2012.
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