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.