CD4 and Cognitive impairment: The risk factors and comorbidities for HAND and implicitly HAD and/or non-HIV-related cognitive impairment include disease factors (i.e., low nadir CD4 cell count, high plasma or CSF HIV RNA, low current CD4, history of HIV-related CNS diseases, longer HIV duration), treatment factors (i.e., low cART adherence, episodes of cART interruption, non-optimal cART regimen, short cART duration), and comorbidities (i.e., positive HCV serostatus with high HCV RNA, history of acute cardiovascular event and presence of cardiovascular risk factors, anemia, and thrombocytopenia).