| Publication Abstract Display | | Type: Published Abstract | | Title: Additive effects of aging and HIV infection on semantic verbal fluency: A view of the cortical hypothesis through the lens of clustering and swtiching. | | Authors: Iudicello JE, Woods SP, Deutsch R, Grant I, and the HNRP Group | | Year: 2011 | | Publication: 2nd International Workshop on HIV & Aging, Baltimore, Maryland | | Volume: Issue: Pages: | | Abstract:Background: Recent findings of the neuropathological changes observed in older HIV-infected adults (e.g., cortical beta-amyloid) suggest that the increased neural burden of HIV and aging may lead to a neuropsychological profile akin to that observed in cortical dementias (e.g., degradation of semantic memory). This study sought to evaluate this hypothesis by examining semantic fluency and its component processes (i.e., clustering and switching) in older HIV-infected adults. As clustering is commonly associated with the integrity of the semantic memory system and may be dissociable from switching, which is more closely associated with executive functions and underlying frontostriatal loops, an examination of these component processes may provide a useful framework to explore the cortical hypothesis in older HIV-infected adults.
Material & Methods: Participants included 257 individuals across 4 demographically matched groups: Younger (i.e., ≤40 years) Healthy (n=93), Younger HIV-infected (n=50), Older (i.e., >50 years) Healthy (n=51), and Older HIV-infected (n=63) individuals. Participants were administered a standard semantic fluency protocol scored according to established clustering and switching guidelines (Troyer et al., 1997) as part of a comprehensive neuropsychological evaluation in our HIV Neurobehavioral Research Program (HNRP).
Results: Jonckheere-Terpstra tests revealed significant additive effects for overall semantic fluency output (p = 0.001) and switching (p = 0.015), with the lowest performance in the Older HIV-infected group. Specifically, the Older HIV-infected cohort demonstrated poorer switching performance relative to the Younger HIV-infected (p = 0.025; d = -0.51) and seronegative groups (p < 0.001, d = -0.70), although performed comparably to the Older HIV-seronegative adults (p = 0.473, d = -0.13). Nevertheless, older HIV-infected individuals with HIV-associated neurocognitive disorders (HAND; n = 27) demonstrated significantly worse switching relative to the unimpaired older HIV-infected participants (p = 0.004, d = -0.68) and older HIV-seronegative group (p = 0.016, d = -0.48). No significant between-group effects were found for cluster size (p = 0.826). Results were not better explained by confounding psychiatric, medical, or HIV-disease characteristics. Within the older HIV-infected adults, poorer switching was associated with learning and executive dysfunction (ps < 0.05), but not with semantic memory impairment (p = 0.226), and was a significant predictor of functional decline (p < 0.05), even when considering potentially confounding variables (e.g., affective distress).
Conclusions: Results suggest that HIV infection and aging may confer adverse additive effects on the executive components of semantic fluency (i.e., switching), which may reflect the combined frontostriatal neuropathological burden of these two conditions. These findings are consistent with the executive (i.e., switching) deficits found in other conditions characterized by frontostriatal damage (e.g., Parkinson’s disease; Troyer et al., 1998), and argue against a posterior neocortical pattern of neuropsychological impairment associated with HIV and aging. Nonetheless, these findings provide support for an increased risk for cognitive impairment and subsequent functional decline in older HIV-infected individuals, and highlight the need to address increased neurocognitive morbidity in this growing subpopulation of the HIV epidemic. |
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