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).