In this respect, future studies should consider not only determinist model of AD (as the amyloid cascade hypothesis), but also recent probabilistic models of AD [56] according to which three variants of AD (autosomal dominant AD, APOE ɛ4-related sporadic AD, and APOE ɛ4-unrelated sporadic AD) feature decreasing penetrance and decreasing weight of the amyloid pathophysiological cascade and increasing weight of stochastic factors (environmental exposures and lower-risk genes). The gene discussed is APOE; the disease is Alzheimer disease.