Aims: To determine whether patients with diabetes without prior myocardial infarction (MI) have the same risk of total coronary heart disease (CHD) events as non-diabetic patients with previous myocardial infarction.
Methods: Using MEDLINE, EMBASE, Cochrane and MeSH in this systematic review and meta-analysis, extensive searching was carried out by cross-referencing from original articles and reviews. The study consisted of cohort or observational studies with hard clinical endpoints, including total CHD events (fatal or non-fatal myocardial infarction), stratified for patients with diabetes but no previous myocardial infarction, and patients without diabetes but with previous myocardial infarction. Studies with less than 100 subjects, follow-up of less than 4 years and/or without provisions for calculating CHD event rates were excluded. The review of articles and data extraction was performed by two independent authors, with any disagreements resolved by consensus.
Results: Thirteen studies were included involving 45,108 patients. The duration of follow-up was 5-25 years (mean 13.4 years) and the age range was 25-84 years. Patients with diabetes without prior myocardial infarction have a 43% lower risk of developing total CHD events compared with patients without diabetes with previous myocardial infarction (summary odds ratio 0.56, 95% confidence interval 0.53-0.60).
Conclusion: This meta-analysis did not support the hypothesis that diabetes is a 'coronary heart disease equivalent'. Public health decisions to initiate cardio-protective drugs in patients with diabetes for primary CHD prevention should therefore be based on appropriate patients' CHD risk estimates rather than a 'blanket' approach of treatment.