The statistical analyses were performed using SPSS for Windows 13.0. Descriptive statistics of all variables were calculated. Some data have been reported as the mean±standard deviation and percentage where necessary. The t-test was performed to compare means between two groups for normally distributed data, and the Mann-Whitney U-test was used for the non-normally distributed data. The χ2-test was used to compare proportions among groups for categorical data. Values of P<0.05 was accepted as statistically significant.