Data were collected and analyzed using SPSS Statistics version 18 (PASW Statistics) and were expressed as mean ± standard deviation (SD), median or number (%). Student’s t-test was used to compare continuous data. Pearson chi-square test or Fisher’s exact test were used to compare categorical data. Multiple logistic regression analysis was used to adjust for potential confounding factors by estimated odds ratio (OR) and 95% confidence interval (CI). Statistically significant differences were defined as p