MAPT and Alzheimer disease: Although some experts have suggested that the low-grade systemic inflammation induced by OA, as well as the faster accumulation of Aβ and the higher Aβ-dependent future tau protein deposition in the primary motor and somatosensory regions, may increase the risk of AD [21–23], a recent Mendelian randomization study based on individuals of European descent did not find a causal relationship between OA and AD [24].