Demographic comparison of samples. Volume of hippocampus is the mean of right and left hippocampus, relative to total intracranial volume and expressed in ‰. Thresholds of p-tau were 75 pg/ml in HCB and 23 pg/ml in ADNI. Thresholds for t-tau were 450 pg/ml in HCB and 93 pg/ml in ADNI. Statistical significance criterion was set to p < 0.05 (in bold significant differences). ⁎Statistical tests were not calculated because different quantitation method was used in each cohort. That made values not to be comparable.