Assuming a two-sided alpha of 0.05, power of 85%, and a 20% drop-out, a sample sized of 30 would be needed for each group. The statistical analysis will be based on the intention-to-treat principle. Continuous variables will be compared by Student t test or Mann-Whitney U test; categorical variables will be analyzed by chi-square test, Fisher's exact test or Kruskal-Wallis H test as appropriate. For comparison between two time points, paired t-test or Wilcoxon signed rank test will be used as appropriate. A statistically significant difference was set at P<0.05.