Statistical analysis
Data analysis was performed using SPSS Statistics 19.0 software. Normally distributed data were presented as the means ± standard deviations (SD). Student's t test was utilized to compare measurements with normal distributions in a random block design. Nonnormally distributed continuous variables were analyzed using the Mann‒Whitney U test, while Tukey's multiple comparison test was used to compare measurements at different points within the same group. Comparisons between 2 groups were performed using the Bonferroni posttests, while proportions were compared using the Chi-square or Fisher's tests. A 