Metabolic syndrome and subclinical carotid damage: a meta-analysis from population-based studies

Aim: Metabolic syndrome (MetS) is a phenotype of growing prevalence in the general population. Information on the association between MetS and vascular damage in this setting is only based on data provided by single reports. We performed a meta-analysis of populationbased studies aimed to assess the association of MetS with carotid atherosclerosis. Design: Studies were identified by the following search terms: 'metabolic syndrome', 'general population,' 'carotid intima-media thickness' (IMT), 'carotid atherosclerosis,' 'carotid damage,' 'ultrasonography.' The OVID-MEDLINE, PubMed, and the Cochrane Central Register of Controlled Trials databases were searched for English-language articles without time restriction up to 30 September 2016. Results: Overall, 34 635 study participants (22.9% with MetS) of both sexes were included in 21 studies (sample size range 182-11 502). Mean common carotid IMT was higher in MetS study participants as compared with their non-MetS counterparts (759 +/- 41 vs. 695 +/- 27mm), the standard means difference being 0.39 +/- 0.05 (confidence interval: 0.29-0.48, P< 0.0001). This was also the case when pooled data were separately analysed according to sex. Differences in carotid IMT were unaffected by the presence of publication bias or single-study effect. Conclusion: Our findings support the view that MetS is a risk factor for early carotid atherosclerosis in members of the general population, regardless of sex. From a practical perspective, the ultrasound search of subclinical carotid disease may refine cardiovascular risk stratification and decision-making strategies in MetS individuals.