Purpose: Controversy exists on whether endothelial function is enhanced in athletes. We sought to systematically review the literature and determine whether endothelial function, as assessed by flow-mediated dilation (FMD), is greater in athletes across all ages relative to that in their age-matched counterparts. Methods: We conducted a systematic search on MEDLINE, Cochrane, Scopus, and Web of Science since their inceptions until July 2013 for articles evaluating FMD in athletes. A meta-analysis was performed to compare the standardized mean difference (SMD) in FMD of the brachial artery between athletes and age-matched control subjects. Subgroup analyses and meta-regression were used to identify sources of heterogeneity. Results: Twenty-one articles were included in this analysis, comprising 530 athletes (452 endurance trained, 49 strength trained, and 29 endurance and strength trained) and 376 control subjects. After data pooling, FMD was higher in athletes than that in control groups (SMD, 0.48; P = 0.008). In subgroup analyses, young athletes (<40 yr) presented increased baseline brachial artery diameter (mean difference, 0.40 mm; P < 0.00001) and similar FMD (SMD, 0.27; P = 0.22) compared with those in controls. In contrast, master athletes (>;50 yr) showed similar baseline brachial artery diameter (mean difference, 0.04 mm; P = 0.69) and increased FMD (SMD, 0.99; P = 0.0005) compared with those in controls. Conclusions: The current meta-analysis provides evidence that master athletes but not young athletes exhibit greater FMD compared with that in age-matched healthy controls, thus suggesting that the association between high levels of exercise training and increased FMD is age dependent.
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