cumulative number of people living with HIV/AIDS has steadily increased. In 2006, the CDC estimated approximately 1.1 million people were living with HIV/AIDS in the United States (CDC, 2008). Over the past decade, the prevalence of HIV/AIDS in the United States has risen disproportionately among some racial and ethnic groups. Slightly more than 50 percent of HIV-positive individuals in the United States are African Americans, and 18 percent are Hispanic/Latino (CDC, 2007). In addition, adolescents and young adults account for an increasing proportion of all new cases of HIV infection. While 29 percent of people living with HIV/AIDS in the United States are between the ages of 13 and 29, this age group accounts for 34 percent of all new cases of HIV (Hall et al., 2008).

Pathogenesis of HIV

HIV damages the immune system by (1) depleting a critical element of the body’s immune system, the CD4+ T-cell pool (CD4 cells), and (2) causing a state of generalized activation and inflammation of the immune system. As a consequence of these two changes, patients with HIV infection are at an increased risk of other infectious diseases and virus-associated cancers as well as an array of noninfectious diseases. The diagnoses and clinical conditions associated with HIV infection are listed in Table C-1 (see Appendix C). In addition to the secondary complications of HIV infection, the virus is capable of directly infecting the nervous system, leading to neurocognitive dysfunction (Grant, 2008).

Comorbidities of HIV

Although the list of opportunistic infections and neoplasms associated with HIV infection is well characterized and has been relatively stable since the beginning of the epidemic, a new set of serious complications of HIV infection has emerged in recent years (Table C-1). These conditions have replaced opportunistic infections as the leading cause of death in patients with HIV infection (Buchacz et al., 2010). It is believed that the ongoing immune activation and inflammation characteristic of HIV infection in patients with or without treatment and manifest by elevated levels of interleukin-6 and D-dimer is responsible, at least in part, for these problems. It has been suggested that HIV infection leads to an accelerated senescence of multiple organ systems, or premature aging. Complicating this picture is the fact that many of these same problems are seen as side effects of some medications used to treat HIV infection.

The presence of comorbidities such as major depressive disorder, other mental disorders, or substance abuse may affect neurocognition in HIV-positive individuals. Cognitive limitations may impair many patients and



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