AD primarily affects people older than 75,[17] and primary age‐related tauopathy, in which tau deposition is directly correlated with cognitive deficits even in the absence of amyloid burden, is commonly observed in the brains of aged individuals.[18] Given that tauopathy has been considered an essential hallmark of neurodegeneration and normal brain aging, such a reduction in Smek1 expression levels in aged brains may be the underlying mechanism of tauopathies that are due to age‐related effects. This evidence concerns the gene PPP4R3A and Alzheimer disease.