Statistical analysis
All statistical analyses were performed using SPSS (version 25.0; IBM Corp., Armonk, NY, USA) and Python 2.7 (Python Software Foundation, Beaverton, OR, USA). Quantitative data with normal distribution are expressed as mean ± standard deviation, while quantitative data with non-normal distribution are expressed as median ± interquartile interval. At the same time, the classification variables are expressed in numbers and percentages. The chi-square test, two independent samples, Student’s 