One retrospective cohort study [18], assessing exenatide and/or insulin on heart failure outcome, included patients with heart failure at baseline, and the proportion of patients with history of heart failure was higher in the insulin group (3.2 %) than in the exenatide group (1.7 %) and exenatide + insulin group (2.4 %), which made the finding from this study biased. Here, INS is linked to heart failure.