PRNP and Alzheimer disease: Analysis of AD risk related to the status of PRNP of the age stratified data indicated that the association to the PRNP M129 allele previously found in the APOE ε4 carriers stratum (see Table 3) was mainly determined by individuals with earlier onset (onset before 74 years old: OR = 2.33, 95% CI: 1.23–4.42, p = 0.009; onset at or after 74 years old: OR = 1.47, 95% CI: 0.66–3.25, p = 0.35) (see Figure 1, right).