Statistical tests
To compare the participants and their distribution in the two different
groups, we used a Student t test, a chi-square test or a Fischer test.
We used a Pearson correlation test to determine the correlation between
age and the number of drugs. Statistical tests were performed with
GraphPad Prism 5.0 (GraphPad Software, San Diego, CA). Values of
probability lower than 5% (p < 0.05) were considered
significant.