Statistical analysis
The data were analysed using SPSS 22.0 statistical software (IBM Corp., Armonk, NY, USA). For categorical variables, Pearson’s chi-square test was performed to determine the difference between the two groups. The independent t test (normal distribution) or Mann-Whitney U test (nonnormal distribution) was used to compare the two groups for continuous variables. For regularly distributed continuous data, the mean and standard deviation (SD) are reported. For nonnormally distributed continuous variables, the median and interquartile ranges (IQR) are shown. For each group, the paired t test or the paired Wilcoxon signed-rank test was used to compare baseline and posttreatment data. The variance inflation factor (VIF) was used to assess collinearity. VIFs of 10 were deemed acceptable (