Four observational studies reported no significant differences between DPP-4 inhibitors and other active treatments for various cardiovascular outcomes such as myocardial infarction, heart failure, ischaemic stroke, and hospitalisation for heart failure [33, 34, 47, 48], although in one study all-cause mortality was significantly lower in users of DPP-4 inhibitors than in controls [48]. This evidence concerns the gene DPP4 and heart failure.