Mediterranean diet and cardiovascular disease: a systematic review and meta-analysis of observational studies

Purpose: To provide evidence of the relationship of Mediterranean diet (MD) on incidence/mortality for cardiovascular disease (CVD), coronary/ischemic heart disease (CHD)/acute myocardial infarction (AMI) and stroke (ischemic/hemorrhagic) by sex, geographic region, study design and type of MD score (MDS). Methods: We performed a systematic review and meta-analysis of observational studies. Pooled relative risks (RRs) were calculated using random-effects models. Results: We identified 29 articles. The RR for the highest versus the lowest category of the MDS was 0.81 (95% CI 0.74–0.88) for the 11 studies that considered unspecified CVD, consistent across all strata. The corresponding pooled RR for CHD/AMI risk was 0.70 (95% CI 0.62–0.80), based on 11 studies. The inverse relationship was consistent across strata of study design, end point (incidence and mortality), sex, geographic area, and the MDS used. The overall RR for the six studies that considered unspecified stroke was 0.73 (95% CI 0.59–0.91) for the highest versus the lowest category of the MDS. The corresponding values were 0.82 (95% CI 0.73–0.92) for ischemic (five studies) and 1.01 (95% CI 0.74–1.37) for hemorrhagic stroke (four studies). Conclusions: Our findings indicate and further quantify that MD exerts a protective effect on the risk of CVD. This inverse association includes CHD and ischemic stroke, but apparently not hemorrhagic stroke.