The Impact of Illicit Drug Use on Adherence to Antiretroviral Therapy among HIV-Infected US Women
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Background: Adherence to ART is associated with improved HIV prognosis and reduced mortality among HIV-infected individuals. Research suggests that adherence is improved with modern single-tablet ART regimens. Few studies have investigated the differential effects of specific illicit drugs on ART adherence; this gap is increasingly important in the era of marijuana legalization. Objective: We estimated the effects of overall illicit drug use, with specific attention to crack and marijuana use, on ART adherence among HIV-infected women in the United States. Methods: The Women’s Interagency HIV Study (WIHS) is the largest prospective cohort study of HIV among US women. Participants in this analysis were ART-exposed HIV-infected women, recruited in three enrollment cohorts: 1994-95, 2001-02 and 2011-12. Illicit drug use and ART adherence were self-reported at paired consecutive semiannual visits from April 2003 to March 2014. We applied the generalized estimating equations method with a log link function and a working exchangeable correlation structure to model sub-optimal (<95%) adherence on exposure data collected at the previous visit. Single-tablet ART regimen was considered as a potential effect modifier. Missing values for drug use and covariates were imputed. Results: The study population was comprised of 1,799 women, who contributed a total of 23,787 person-visits to the analysis. Adjusted for calendar time, baseline age, race, education, marital status, parity, AIDS diagnosis, depressive symptoms, HIV-related clinical symptoms, STI, drinking, current smoking, ever injection drug use, CD4+ count, detectable HIV viral load, class of ART regimen, single-tablet ART regimen, and enrollment cohort, illicit drug use was significantly associated with sub-optimal adherence (Prevalence ratio (PR)=1.20; 95% confidence interval (CI): 1.10 to 1.31). Compared to non-drug users, women using crack, but not marijuana (PR=1.39; 95% CI: 1.18 to 1.64), both crack and marijuana (PR=1.48; 95% CI: 1.24 to 1.77), and other drugs (PR=1.41; 95% CI: 1.19 to 1.67) all had significantly higher prevalence of sub-optimal adherence. No significant association was seen for marijuana use only (PR=1.05; 95% CI: 0.94 to 1.16). No significant interaction between illicit drug use and single-tablet regimen was seen. Conclusions: In this cohort of HIV-infected women, crack use was significantly associated with about 40% increase in the prevalence of sub-optimal adherence to ART, with marijuana use only having no significant impact on adherence. These findings highlight the importance of assessing, monitoring, and intervening on illicit drug use, and in particular crack use, to maintain effective ART adherence and consequent health outcomes among HIV-infected individuals.