Statistical analysis
Continuous variables are presented as mean ± standard deviation (SD) and were compared with Student t or Mann–Whitney test. For paired data, paired Student t and Wilcoxon signed rank test were used. Categorical variables are expressed as numbers and percentages and were compared by use of Pearson’s χ2 or Fisher’s exact test. Statistical significance was set at a 2-tailed probability level of <0.05. Statistical analyses were performed using IBM SPSS Statistics (version 24.0; IBM Corp, Armonk, NY).