Statistics
Statistical analysis was performed using the Statistical Package for the Social Sciences version 26.0 software (SPSS Inc., Chicago, IL, USA). The chi-square or Fisher’s exact tests for categorical variables were used. The Shapiro–Wilk test was used to test the distribution of normality. The differences between groups were analysed using Student’s t-test or the Mann–Whitney U test when only two groups were compared, or by the Kruskal-Wallis H test when more than two groups were compared. If there was a significant difference between multiple groups, the Bonferroni correction for post hoc multiple comparisons was used. Correlations between variables were analysed using the Spearman correlation test. P-values < 0.05 (two-sided) were considered statistically significant.