Cases qualifying for both DSM-5 major NCD and DSM-IV dementia were also more likely to carry at least one APOE e4 allele (55.2%) compared to those meeting only the DSM-5 major NCD diagnosis (14.6%) (p < 0.001), with the latter being statistically not different from the APOE e4 allele frequency in cognitively normal participants (25.8%) (p > 0.05). Here, APOE is linked to dementia.