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.