Phosphorylated tau (p-tau) and total tau (t-tau) in saliva were investigated in four studies, which altogether included 181 subjects with AD, 123 subjects with amnestic mild cognitive impairment (aMCI), twenty subjects with PD, sixteen subjects with frontotemporal dementia (FTD), and 317 healthy controls. This evidence concerns the gene MAPT and frontotemporal dementia.