Considering prior evidence pointing towards an association of circulating IL-6 levels with cerebrovascular events and vascular cognitive impairment [42,43], as well as towards additive or synergistic effects of vascular pathology on AD-related cognitive decline [44], we hypothesized that potential relationships of genetic predisposition for high circulating levels of IL-6 with AD pathology might be confounded, or mediated, by vascular pathways. This evidence concerns the gene IL6 and Alzheimer disease.