Statistical Analysis
Continuous variables are expressed as the mean ± SD and categorical variables were reported as counts and frequencies. Intergroup differences were compared by using analysis of variance or the Kruskal-Wallis test for overall comparisons and the T-test or Mann-Whitney U test for two-group comparisons. Statistical analyses were performed with SPSS statistical software version 11.0 (Cary, North Carolina). All statistical tests were 2 sided, and a p value < 0.05 was considered significant.