Statistical analysis
Continuous variables (e.g., age) were given as mean±SD, and were
analyzed with t tests if they conformed to a normal distribution and
Mann-Whitney U tests if not. Comparisons between more than 2 groups made
with one-way analysis of variance. Categorical variables (e.g., gender)
were compared using the χ2 test or the Fisher exact
test. P <0.05 was considered significant. All analyses were
performed using JMP Pro statistical software (version 10, SAS Inc, Cary,
NC) and Microsoft Excel.