Estimated premorbid intelligence mediates neurobehavioral change in individuals infected with HIV across 12 months.

This study tested whether estimated premorbid intelligence moderates worsening neurobehavioral dysfunction in HIV infection. 155 homosexual men (54 controls, 49 HIV+ asymptomatic, 24 HIV+ symptomatic, 28 AIDS) with stable disease status were tested on measures of executive function at baseline and 12-month follow-up. Premorbid intelligence was estimated on the basis of a demographically-based regression equation (Hamsher, 1984), and participants were classified as average or above-average intelligence. Regardless of disease status, participants with above-average IQ showed no declines on measures of executive function across time. In contrast, among those with average IQ, symptomatic groups showed declines, whereas the asymptomatic group did not. The findings support the hypothesis that estimated premorbid intelligence mediates declines in neuropsychological function in patients with stable HIV status. These findings are consistent with theoretical models of cognitive reserve capacity.