McDade and Bateman (2017) found that patients with high expression of Aβ42 in peripheral blood had an increased risk of dementia after 5 years. Assini et al. (2004) showed that women with mild cognitive impairment (MCI) had elevated Aβ42 in peripheral blood and suggested that elevated levels of Aβ42 and a decreased Aβ42/Aβ40 ratio in peripheral blood were risk factors for AD. Recently, a large study led by Fiandaca et al. (2015) showed that the tau concentration in peripheral blood was higher in patients with AD and was significantly correlated with future cognitive decline. The gene discussed is MAPT; the disease is Alzheimer disease.