Statistical analysis
All statistical analyses were performed using Statistical Package for the Social Sciences (SPSS) version 20.0 software (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.). Continuous variables with normal distribution are presented as mean ± SD. Non-normal variables are presented as median (interquartile range), and categorical data are presented as percentages (%). Continuous variables were analyzed using the independent-sample 