APOE and Alzheimer disease: The APOE ε4 allele was associated with lower mtDNAcn (p = 8.0 × 10− 7, random effects meta-analysis), but this association was attenuated considerably when adjusting for pathologies (p = 0.014, random effects meta-analysis) (Table 2) suggesting that a large fraction but not the complete APOE ε4 effect on mtDNAcn is mediated via AD pathology.