Statistical analysis-
On the basis of previous validation studies, which defined normal endothelial function as RHI >1.67 and revealed a variance of ~ 15% in RHI measurement, 11 subjects in each group were required to detect a difference between groups of at least 15% (corresponding to absolute difference in RHI of 0.25 units) with 80% power and 5% type 1 error 21,22. Normally distributed data were described as mean ± standard deviation (SD), and non-normally distributed data were described as median and intra-quartile range (IQR). Univariate analyses were performed by t-test or Mann-Whitney test as appropriate for continuous variables and by Chi-square or Fisher’s exact test for categorical variables. Significant difference was defined as p<0.05. All analyses were conducted using SPSS 24 (SPSS Inc., Chicago, IL).