Linear regression models amongst the MCI and AD individuals demonstrated that decreased Aβ levels (ß-coefficient = −0.08, 95% Confidence Interval (CI) = −0.01 to −0.003, p<0.01) and increased p-tau levels (ß-coefficient = 0.02, 95% CI = 0.006 to 0.03, p<0.01) significantly predicted hippocampal atrophy rate. The gene discussed is MAPT; the disease is Alzheimer disease.