Statistical analysis
Statistical analyses were conducted utilizing statistical package software (IBM SPSS Statistics for Windows, v21.0. IBM Corp., Armonk, NY). The normality of data was examined using the Shapiro-Wilk normality test. In normally distributed data, independent t-test and one-way ANOVA tests were performed for comparisons. In non-normally distributed data, Mann-Whitney U and Kruskal-Wallis tests were performed for comparisons. Logistic regression and Cox regression analyses were performed to identify the association of risk factors. Statistical significance was assumed at p< 0.05.