can affect a variety of brain regions, and the illness can take on many different trajectories
depending on associated comorbidities and cons equences of HIV, the overall course of an
NCD due to HIV infection has considerable heterogeneity. A subc ortical neurocognitive
profile may interact with age over the life course, when psychomo tor slowing and motor
impairments such as slowed gait may occur as a consequence of other age-related condi-
tions so that the overall progression ma y appear more pronounced in later life. 
In developed countries, HIV disease is primar ily a condition of adults, with acquisition
via risky behaviors (e.g., unprotected sex, inje ction drug use) beginning in late adolescence
and peaking during young and middle adulth ood. In developing countries, particularly
sub-Saharan Africa, where HIV testing and an tiretroviral treatments for pregnant women
are not readily available, perinatal transmis sion is common. The NCD in such infants and
children may present primarily as neurodevelopment al delay. As individuals treated for
HIV survive into older age, additive and in teractive neurocognitive effects of HIV and
aging, including other NCDs (e .g., due to Alzheimer’s dise ase, due to Parkinson’s dis-
ease), are possible. 
Risk and Prognostic Factors
Risk and prognostic factors for HIV infection. Risk factors for HIV infection include injec-
tion drug use, unprotected sex, and unprotecte d blood supply and othe r iatrogenic factors. 
Risk and prognostic factors for major or mild neurocognitive disorder due to HIV in-
fection. Paradoxically, NCD due to HIV infection ha s not declined significantly with the
advent of combined antiretrov iral therapy, although the most  severe presentations (con-