However, an earlier prospective study of a HIV-infected cohort with mean absolute CD4+ cell counts of approximately 350/mm3, “sufficient to avoid opportunistic infection” (Corder et al. 1998), reported a statistically significant excess of cognitive impairment symptoms and peripheral neuropathy in individuals with the ApoE4 isoform, some of whom had been treated with zidovudine ART. Here, APOE is linked to Cognitive impairment.