Statistical analysis
We used SPSS for the statistical analyses.28 We present data as
means with standard deviations or as percentages. We compared
continuous data by using Student’s t test (and non-parametric
tests if appropriate) and categorical data by using the 2 test or
Fisher’s exact test. We considered associations with P < 0.05 to be
significant. We also calculated relative risks and associated 95%
confidence intervals