Finally, we apply our methods to the Alzheimer’s Disease Neuroimaging Initiative (ADNI) study to compare cerebrospinal fluid (CSF) biomarkers between dementia and non-dementia cohorts, which offers a fascinating insight into the differences between covariance structures of biomarkers amyloid β(1−42)(Aβ42), total tau (tau), and phosphorylated tau (ptau) for given values of age, sex, and years of education. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.