The effects of low literacy and cognitive impairment on medication adherence in HIV-positive injecting drug users.

Low literacy and cognitive impairment have each been separately identified as risks for non-adherence in HIV infection. However, no studies to date have evaluated these skill deficits in combination. We therefore characterized the nature of literacy and cognitive skills in a sample of HIV-positive injecting drug users and assessed their combined effects on adherence. A community-recruited sample of 57 HIV-positive injecting drug users completed the study. Participants were classified into one of four groups based on their performance on a reading test and a brief neuropsychological battery: high literacy/high cognition, low literacy/high cognition, high literacy/low cognition and low literacy/low cognition. Chi-square and bivariate analyses were used to characterize the literacy and cognitive skills of the overall sample and logistic regression analysis was used to test the relation of the four groups to non-adherence (< 95%). In general, performance on measures of literacy and cognitive functioning were below average, with severe deficits noted in psychomotor functioning. Additionally, after adjusting for recent cocaine use, those classified as low literate/low cognition were over nine times more likely to be non-adherent than the referent high literate/high cognition group. Low literacy and cognitive impairment placed HIV-positive drug users at high risk for non-adherence, even after adjusting for recent cocaine use. The findings suggest that targeted interventions to improve these skill deficits in this population may help to improve adherence to HIV medications.