Statistical Analysis
Data are presented as mean ± standard deviation. Continuous variables were tested with the Kolmogorov-Smirnov test for normal distribution. Categorical variables are given as frequencies and percentages. A chi-square test was used for comparison of categorical variables between the groups. Student’s t-test was performed for comparison of normally distributed continuous variables and Mann-Whitney U test for non-normal distribution. Statistical significance was assumed when the null hypothesis could be rejected at P < 0.05. All P-values are the results of two-sided tests. Statistical analyses were conducted using R (version 3.4.1).