Moreover, the relationship between the APOE genotype and AD is not only determined by genetic factors but is also modulated by complex gene–environment interactions such as diet, physical activity, cognitive stimulation, and cardiovascular health, which may modify the risk conferred by the APOE genotype; for example, Panza et al. reported a significant reduction in serum APOE levels from APOE ε2 to ε4 carriers. The gene discussed is APOE; the disease is Alzheimer disease.