APOE and Cognitive impairment: The HIV-infected and SN subject groups had similar ages and prevalence of the Apoε4 allele; 29 (42%) of HIV-infected subjects had HAND while 4 (6%) of SN controls had cognitive deficits “comparable to HAND.” Chang et al. did observe poorer cognitive performance (verbal fluency, learning, executive function, memory) in HIV-infected Apoε4 carriers compared to HIV-infected noncarriers and SN controls.