Statistical analysis
Statistical analyses were performed using SPSS version 22.0. Statistics of continuous variables conforming to a normal distribution (evaluated by skewness and kurtosis) were described as mean ± standard deviation. One‐way analysis of variance (ANOVA) was used for between‐group comparisons, and the least significant difference‐t method was used for two‐way comparisons. For continuous variables with skewed distributions, statistics were expressed as median and interquartile spacing, and the non‐parametric Kruskal‐Wallis H‐test was employed for two‐way comparisons between groups. Count data were expressed as frequency (rate) and compared using the χ