Participants enrolled in the United States/Canada ( odds ratio @ , confidence intervals @-@ @ , vs. Latin America ) , taking more ( @ + ) prescription medications ( odds ratio @ , confidence intervals @-@ @ , vs. @-@ medications ) , and scoring lower on the Stroke Specific Quality of Life scale ( odds ratio @ , confidence intervals @-@ @ , per @ points ) were more likely to withdraw or become lost to follow-up in the study vs. completing the study on assigned antiplatelet therapy .