In the present naturalistic study, we aimed to examine if detectable virus in blood, current CD4 count, nadir CD4, and increase in CD4 count after drug therapy for HIV, as well as pulmonary tuberculosis was associated with cognitive performance.

The study included 229 HIV participants, where we had data on HIV status, virus in plasma, current and nadir CD4 count, and diagnosis of pulmonary tuberculosis, which was treated within the last 6 months. Of the 229 participants 38 had a detectable HIV viral load in their blood. Detection level was viral load >= 40 cells/ml. All participants were treated with highly active antiretroviral drugs (ART) at the time of testing. Regarding tuberculosis, all (22 participants) were on treatment.

Using the Independent T test, we first compared the neurocognitive performance of the 229 HIV-seropositive participants with 324 seronegative participants. The participants were examined with 16 tests which were divided into seven cognitive domains: Executive functioning, working memory, learning, recall, verbal fluency, fine motor, speed of information processing and a composite General mean T-score.   Multilinear regressions were performed. The dependent variable was the Global mean T-score (overall composite score). Independent variables were age, education, sex, viral load, tuberculosis, nadir, current and increase in CD4 count from before to after ART.

In comparing the results between the HIV-positives and HIV-negatives, the former performed worse on all the cognitive domain T-scores, except for the motor domain. In all,  36% of the seropostives were seen to be cognitively impaired as measured by a Global Deficit Score, compared to 15.6% of the HIV seronegatives.

We did not find any direct effect of viral suppression in the blood on cognitive performance. However viral load was as expected associated with an increase of CD4 cells. In our analyses, the increase in CD4 cells was the best predictor of cognitive performance (p<.001). For every increase in CD4 count (before and after drug therapy) by 100, there is an increase in the Global mean score by 0.53 points, after adjusting for age, education, sex, viral load and tuberculosis. Not all participants had an increase in their CD4 count after medication. Twenty-one participants had a decrease in CD4 count and two had the same value after medication.

Increase in CD4 count is important for cognitive functioning after drug therapy in HIV-infection. The results from the study will be discussed.