MAPT and early-onset autosomal dominant Alzheimer disease: Aging is a complex and irreversible process that occurs in multiple organs and cellular systems and is characterized by a decrease in brain weight and volume, loss of synapses, and ventricular widening in specific areas, which are accompanied by deposits of amyloid beta and neurofibrillary tangles via hyperphosphorylation of tau protein, which can produce cognitive impairment, both of which are characteristic Alzheimer’s disease biomarkers [37].