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  3rd International Workshop on HIV and Aging
November 5-6, 2012
Baltimore, MD
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Higher VACS Index Linked to Neurocognitive Impairment With HIV
  3rd International Workshop on HIV and Aging, November 5-6, 2012, Baltimore
Mark Mascolini
A higher Veterans Aging Cohort Study (VACS) score, which predicts mortality in people with HIV, was associated with neurocognitive impairment in HIV-positive people tested at the University of California, San Diego (UCSD) [1]. The UCSD team noted, though, that the association is modest and its clinical significance remains to be established. Among the 7 VACS components, older age, lower hemoglobin, and hepatitis C virus (HCV) coinfection most strongly predicted neurocognitive impairment.
Veterans Administration researchers designed the VACS index to assess the impact of HIV and non-HIV variables on morbidity and mortality in people with HIV. VACS predicts mortality and some types of morbidity in HIV-positive people [2-4], but its potential association with neurocognitive function had not been assessed until this study. The index combines age, two HIV markers (CD4 count, viral load), and four non-HIV markers (hemoglobin, liver fibrosis [FIB-4], kidney function [estimated glomerular filtration rate], HCV infection). The score ranges from 0 to 160, with a higher score indicating worse clinical status.
This cross-sectional study involved 1274 HIV-positive people, all of whom had 7-domain neurocognitive testing. The researchers defined neurocognitive impairment as a global deficit score at or above 0.5. They also calculated a VACS score for each study participant.
Age averaged 41.9 in the study group, 85% were men, 53% white, 24% Hispanic, and 18% black. Median current CD4 count stood at 370 (interquartile range [IQR] 285 to 581), nadir CD4 count at 136 (IQR 25 to 295), HIV duration at 8.2 years (IQR 3.5 to 14.1), and antiretroviral exposure at 18.4 months (IQR 0.9 to 55.6). Two thirds of study participants were taking antiretrovirals, and 44% had a detectable viral load in plasma.
Of the 1274 study participants, 42% had neurocognitive impairment. VACS index averaged 24.9 (standard deviation 20.6, range 0 to 131). Every 10-unit higher VACS index raised the odds of neurocognitive impairment 20% (odds ratio [OR] 1.2, 95% confidence interval [CI] 1.1 to 1.3). That association held true when the researchers added AIDS to the statistical model. AIDS raised chances of neurocognitive impairment 50% (OR 1.5, 95% CI 1.2 to 1.9).
In a subset of 559 people with an undetectable viral load, VACS also conferred 20% higher odds of neurocognitive impairment in models with or without AIDS. In this subset AIDS no longer independently predicted neurocognitive impairment (OR 1.13, 95% CI 0.7 to 1.6).
In the whole study group, higher VACS was independently associated with worse performance in each of the 7 neurocognitive domains. That association was relatively small for verbal fluency (OR 1.06, 95% CI 1.00 to 1.13) and recall (OR 1.09, 95% CI 1.03 to 1.15) and strongest for information processing speed (OR 1.17, 95% CI 1.11 to 1.24) and motor skills (OR 1.16, 95% CI 1.09 to 1.23).
Of the 7 VACS components, older age (P = 0.01), low hemoglobin (P < 0.01), and HCV (P = 0.02) strongly predicted neurocognitive impairment in a statistical model without AIDS. With AIDS added to the model, hemoglobin (P = 0.02) and HCV (P < 0.01) remained significantly associated with neurocognitive impairment. Among the 559 study participants with an undetectable viral load, only low hemoglobin predicted neurocognitive impairment in the model without AIDS (P = 0.02) and the model with AIDS (P = 0.03).
The UCSD team concluded that a higher VACS index is associated with neurocognitive impairment. But because odds ratios were modestly positive, they cautioned that "the clinical significance of this association is yet to be established."
1. Marquine MJ, Moore DJ, Gouaux DJ, et al. Higher veterans aging cohort study (VACS) index scores are associated with concurrent risk of neurocognitive impairment. 3rd International Workshop on HIV and Aging. November 5-6, 2012, Baltimore. Abstract O_03.
2. Justice AC, McGinnis KA, Skanderson M, et al. Towards a combined prognostic index for survival in HIV infection: the role of 'non-HIV' biomarkers. HIV Med. 2010;11:143-51. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3077949/. 3. Justice AC, McGinnis KA, Skanderson M, et al. Towards a combined prognostic index for survival in HIV infection: the role of 'non-HIV' biomarkers. HIV Med. 2010;11:143-151.
4. Tate JP, Justice AC, Hughes MD, et al. The VACS index: an internationally generalizable risk index for mortality after one year of antiretroviral therapy. AIDS. 2012 Oct 22. Epub ahead of print.