Injection drug use is a significant public health crisis with adverse health outcomes, including increased risk of human immunodeficiency virus (HIV) infection. Comorbidity of HIV and injection drug use is highly prevalent in the United States and disproportionately elevated in surrounding territories such as Puerto Rico. While both HIV status and injection drug use are independently known to be associated with cognitive deficits, the interaction of these effects remains largely unknown. The aim of this study was to determine how HIV status and injection drug use are related to cognitive functioning in a group of Puerto Rican participants. Additionally, we investigated the degree to which type and frequency of substance use predict cognitive abilities.

96 Puerto Rican adults completed the Neuropsi Attention and Memory-3rd Edition battery for Spanish-speaking participants. Injection substance use over the previous 12 months was also obtained via clinical interview. Participants were categorized into four groups based on HIV status and injection substance use in the last 30 days (HIV+/injector, HIV+/non-injector, HIV/injector, HIV-/non-injector). One-way analysis of variance (ANOVA) was conducted to determine differences between groups on each index of the Neuropsi battery (Attention and Executive Function; Memory; Attention and Memory). Multiple linear regression was used to determine whether type and frequency of substance use predicted performance on these indices while considering HIV status.

The one-way ANOVAs revealed significant differences (p’s < 0.01) between the healthy control group and all other groups across all indices. No significant differences were observed between the other groups. Injection drug use, regardless of the substance, was associated with lower combined attention and memory performance compared to those who inject less than monthly (Monthly: p = 0.04; 2-3x daily: p < 0.01; 4-7x daily: p = 0.02; 8+ times daily: p < 0.01). Both minimal and heavy daily use predicted poorer memory performance (p = 0.02 and p = 0.01, respectively). Heavy heroin use predicted poorer attention and executive functioning (p = 0.04). Heroin use also predicted lower performance on tests of memory when used monthly (p = 0.049), and daily or almost daily (2-6x weekly: p = 0.04; 4-7x daily: p = 0.04). Finally, moderate injection of heroin predicted lower scores on attention and memory (Weekly: p = 0.04; 2-6x weekly: p = 0.048). Heavy combined heroin and cocaine use predicted worse memory performance (p = 0.03) and combined attention and memory (p = 0.046). HIV status was not a moderating factor in any circumstance.

As predicted, residents of Puerto Rico who do not inject substances and are HIVnegative performed better in domains of memory, attention, and executive function than those living with HIV and/or inject substances. There was no significant difference among the affected groups in cognitive ability. As expected, daily injection of substances predicted worse performance on tasks of memory. Heavy heroin use predicted worse performance on executive function and memory tasks, while heroin-only and combined heroin and cocaine use predicted worse memory performance. Overall, the type and frequency of substance is more predictive of cognitive functioning than HIV status.