A body of neuropathological evidence shows that key features of Alzheimer's disease, such as extracellular deposits of amyloid β and intraneuronal aggregates of hyperphosphorylated tau, are not more frequent in patients with type-2 diabetes compared to individuals without (Arvanitakis et al., 2006; Abner et al., 2016; Pruzin et al., 2018). This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.