While the numbers of HIV infected veterans under the age of 50 are declining, the percentage of HIV infected veterans over the age of 50 is increasing with the largest percentage increases in the 50-59 age group and the 70+ age group. With increasing incidence rates of new cases among individuals over 50 years of age and the longer life expectancies of the current HIV-infected population, it becomes increasingly important to better understand the impact of the aging process on the clinical and behavioral manifestations of HIV/AIDS.

The project seeks to determine the effect of age on neuropsychological performance in HIV+ persons. This objective seeks to determine the degree to which older age represents an independent risk factor for neuropsychological impairment in HIV infected persons, with a particular emphasis on those cognitive processes that are preferentially impacted by both the normal aging process as well as HIV infection. Additionally, another aim of the study is to determine the impact of neuropsychological decline on everyday functional abilities among older vs. younger HIV+ adults. This objective seeks to determine the effects of advancing age and neuropsychological impairment on the ability of HIV+ persons to discharge more demanding requirements of independent living (e.g., driving, financial management, medication adherence). The project will last for a duration of 5 years. Subjects will be followed for 4 years, those who are enrolled in Year 1 will complete the study in Year 4 whereas those who enter in Year 2 will complete the study in Year 5.

HIV Infections

Over the past several years the HIV epidemic has changed from a disease primarily of younger, gay/bisexual, Caucasian men to one increasingly affecting people of color, women, and, of specific relevance to this application, the older adult. Indeed, the number of AIDS cases in individuals over the age of 50 has more than tripled over the last several years, with the CDC now estimating that in the United States 15% of all patients with AIDS are over age 50.1 There is reason to believe that the incidence, clinical manifestations and course of HIV-associated CNS dysfunction may differ as a function of age. Since the mid 1980's VA has been at the vanguard of institutions engaged in research and clinical care of HIV-infected adults. With specific regard to the issue of aging and HIV, HIV-infected veterans have tended to be significantly older than patients drawn from the general community. For example, at the West Los Angeles VA 303 of the 583 (52%) HIV-infected patients being followed by the Infectious Disease clinic are over the age of 50. Across the entire VA system, there are nearly twice as many HIV infected veterans over the age of 70 than under 30 years of age. 2 Yet, the vast majority of research conducted to date has been on younger adults

the degree to which such data will generalize to the older veteran population is unclear. Also unclear is whether advancing age confers an independent risk for cognitive impairment in HIV-infected persons. Additionally, the functional impact (i.e., impact on daily functioning such as driving ability, financial management, or medication adherence) of cognitive impairment in this group remains unknown. Exploratory studies performed in the applicants' laboratory have provided preliminary support for the hypothesis that advancing age will potentiate the deleterious neurocognitive effects of HIV infection. Given the "graying" of the HIV epidemic, particularly among the veteran population, research examining neurocognition among older HIV-infected veterans as well as the functional "real world" impact of such deficits is of great relevance to the VA mission. The results from this study could provide important insights into interactions of age and HIV disease, and will identify targets for intervention in advance of the burgeoning population of older infected persons.

SPECIFIC OBJECTIVES AND HYPOTHESES

Objective 1. To Determine the Effect of Age on Neuropsychological Performance in HIV+ Persons This objective seeks to determine the degree to which older age represents an independent risk factor for neuropsychological impairment in HIV infected persons, with a particular emphasis on those cognitive processes that are preferentially impacted by both the normal aging process as well as HIV infection.

Hypothesis 1.1 Controlling for potential confounding factors such as substance use and length of infection, there will be an interaction between effects of age and HIV serostatus on neuropsychological performance, and this will be evident both cross-sectionally and longitudinally. Specifically, we expect to find that older HIV+ individuals will exhibit greater rates of neuropsychological impairment (using age-corrected test norms) than younger HIV+ persons. Neurocognitive functions subserved by frontal-subcortical systems that are sensitive to the effects of both aging and HIV infection (learning, motor and psychomotor speed, executive function) will be disproportionately affected among the older HIV+ participants. While the synergistic effects of HIV and age will be evident on a cross sectional basis, they will be most pronounced when examined longitudinally over the course of the study.

Objective 2. To Determine the Impact of Neuropsychological Decline on Everyday Functional Abilities Among Older vs. Younger HIV+ Adults This objective seeks to determine the effects of advancing age and neuropsychological impairment on the ability of HIV+ persons to discharge more demanding requirements of independent living (e.g., driving, financial management, medication adherence).

Hypothesis 2.1 In both older and younger HIV+ persons, neuropsychological impairment will be strongly associated with increased impairment on measures of daily functioning. However, significant age by neuropsychological impairment interaction effects also are expected, indicating greater functional impact of neuropsychological impairment in the older HIV+ group. Although comorbid medical disabilities, depression, and drug/alcohol use also will have adverse effects on everyday functioning, the effects of neuropsychological impairment will remain significant even after controlling for these risk factors. While the synergistic effects of HIV and age will be evident on a cross sectional basis, they will be most pronounced when examined longitudinally.

Hypothesis 2.2 As a group, older HIV+ participants will demonstrate better medication adherence than will younger participants. However, older HIV+ participants who demonstrate neuropsychological impairment will evidence significantly worse adherence than all other HIV+ subgroups (older unimpaired, younger impaired, younger unimpaired). While adherence rates will drop for all participants over time, the steepest decline will be seen among neuropsychologically impaired older HIV+ participants.