Data sources, eligibility, and Data extraction
We searched in Medline (via PubMed), Cinahl (via Ebsco), Scopus, and Web of Sciences until December 2020 using the predefined search terms aspirin, cardiovascular disease (CVD), diabetes, efficacy, OR meta-analysis until December 2020. Ten trials included in a previous meta-analysis; 12 were also identified and included in the present meta-analysis. The inclusion criteria include only randomized clinical trials of Aspirin, except one which was a cross-sectional study. The Aspirin was compared with placebo or no treatment in patients with or without diabetes, and without a history or clinical evidence of CVD; screened for the eligibility. Studies had to be controlled (placebo or control group) but could be open-label or blinded. The patients above 18 years of age either who have diabetes was included, and full text was acquired for further evaluation if the citation was deemed pertinent. Studies were excluded if the patient was below 18 years of age, non-randomized studies comparing Aspirin with another antiplatelet agent, or use of Aspirin in combination with any other antiplatelet drug compared with placebo.
The data extracted from the selected trials included appropriate study-level information on type of study design; baseline of the study period, source of participants; total population including proportion of men; location; age range at baseline; allocation concealment; blinding; intervention and dosage; medication compliance; duration of the therapy, completeness of follow-up and also included trial population with diabetes as described in Table 1.
The quality of risk involved was assessed using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) criterion. If any disagreement arose, it was resolved by consensus among reviewers24.
The outcomes of major adverse cardiovascular event/s [MACE; defined as a combination of nonfatal myocardial infarction (MI), nonfatal stroke and cardiovascular death], other cardiovascular outcomes, all-cause mortality, and adverse events; and risk estimates were also evaluated in diabetic patients to rule out the efficacy of Aspirin to placebo.