Antiviral Therapy 9:407-414
Psychosocial determinants of adherence to highly active antiretroviral therapy among injection drug users in Vancouver Thomas Kerr1,2*, Anita Palepu3,4, Gordon Barnes5, John Walsh6, Robert Hogg2,7, Julio Montaner2,4, Mark Tyndall2,4 and Evan Wood2,7 1
Canadian HIV/AIDS Legal Network, Montreal, Que., Canada British Columbia Centre for Excellence in HIV/AIDS, St Paul’s Hospital, Vancouver, BC, Canada 3 Centre for Health Evaluation and Outcome Sciences, St Paul’s Hospital, Vancouver, BC, Canada 4 Department of Medicine, University of British Columbia, Vancouver, BC, Canada 5 Department of Human and Social Development, University of Victoria, Victoria, BC, Canada 6 Department of Educational Psychology and Leadership Studies, University of Victoria, Victoria, BC, Canada 7 Department of Healthcare and Epidemiology, University of British Columbia, Vancouver, BC, Canada 2
Corresponding author: Tel: +1 514 397 6828, ext 222; Fax: +1 514 397 8570; E-mail:
[email protected]
Background: Sub-optimal adherence to highly active antiretroviral therapy (HAART) among injection drug users (IDUs) is a significant concern. As such, there is an urgent need to identify psychosocial determinants of adherence that can be incorporated into interventions designed to promote optimal adherence. Objective: To identify psychosocial determinants of adherence to HAART, as well as self-reported reasons for missing doses of HAART among HIV-infected IDUs. Methods: We developed an eight-item adherence selfefficacy scale comprised of two sub-scales: adherence efficacy and self-regulatory efficacy. We examined correlates between adherence self-efficacy, outcome expectations, socio-demographic characteristics, drug use and risk behaviours, social support and HAART adherence among 108 HIV-infected participants in the Vancouver Injection Drug Users Study (VIDUS). Pharmacy-based adherence to HAART was obtained through a confidential record linkage to the province of
British Columbia’s HIV/AIDS Drug Treatment Program. Participants were defined as adherent if they picked-up 95% of their HAART prescriptions. Participants were also asked to indicate reasons for missing doses of HAART. Logistic regression was used to identify the factors independently associated with adherence to HAART. Results: Seventy-one (66%) HIV-infected IDUs were less than 95% adherent. Forgetting was the most frequently cited reason (27%) for missing doses of HAART. Factors independently associated with adherence to HAART included adherence efficacy expectations [OR=1.8 (95% CI: 1.0–3.1); P=0.039] and negative outcome expectations [OR=0.8 (95% CI: 0.7–0.9); P=0.027]. Conclusions: We found low rates of adherence to HAART among IDUs. Psychological constructs derived from selfefficacy theory are highly germane to the understanding of adherence behaviour, and interventions that address these constructs should be developed and tested among HIV-infected drug users.
Introduction The advent of highly active antiretroviral therapy (HAART) has significantly altered the course of HIV disease, producing substantial reductions in both AIDS-related morbidity and mortality [1–3]. However, in North America these advances have emerged amid growing concerns regarding inequitable access and lower levels of adherence among populations affected during later stages of the HIV epidemic [4–6]. Among those known to have low rates of adherence to HAART and consequently poor AIDS-related health outcomes are injection drug users (IDUs) [1,7,8]. Low levels of adherence among IDUs have resulted in low ©2004 International Medical Press 1359-6535/02/$17.00
rates of virological suppression among this population, and consequently high rates of AIDS-related morbidity and mortality [1,7]. Low levels of adherence to HAART among IDUs also indicate potentially adverse outcomes for public health due to the increased potential for the development of drug resistance and the transmission of resistant virus to others [9,10]. While there has been a rapidly growing body of literature addressing issues associated with adherence to HAART [11–13], there remains an urgent need to identify population-specific determinants of adherence that can inform interventions, particularly for highly 407
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marginalized populations [14]. In particular, there is a need to identify relevant psychosocial variables that are known to be amenable to improvement via established interventions. Further, the identification of psychosocial variables that may predict poor adherence to HAART may help to identify patients who should receive adherence interventions prior to initiating treatment. In particular, theories such as self-efficacy, which have been applied successfully in addressing a range of health-related behaviours [15,16], have not received adequate attention in adherence literature. Therefore, the present study was undertaken to identify psychosocial characteristics associated with adherence to HAART among IDUs, as well as self-reported reasons for missing doses of HAART, in a setting that delivers HAART and AIDS care free of charge. We hypothesize that adherence will be predicted by specific psychosocial characteristics, including adherence self-efficacy, outcome expectations and social support.
Methods The Vancouver Injection Drug Users Study (VIDUS) Beginning in May 1996, persons who had injected illicit drugs at least once in the previous month and resided in the Greater Vancouver region were recruited into VIDUS, a prospective cohort study of IDUs that has been described in detail previously [17,18]. Subjects have been recruited through selfreferral and street outreach efforts. Eligible subjects were those who had injected illicit drugs at least once in the previous month, resided in the Greater Vancouver area and provided written informed consent. All participants are informed of the nature of the study and asked to sign a consent form that permits linkages with external medical records. At baseline and semi-annually, participants provided blood samples and completed an interviewer-administered questionnaire. The questionnaire is designed to elicit demographic data and information about drug use, HIV risk behaviours and drug treatment. Participants are reimbursed $20 for each study visit, at which time referrals are provided for universal medical care, HIV/AIDS care, and available drug and alcohol treatment. The VIDUS study has ethical approval from the University of British Columbia/Providence Health-care Office of Research Services. The present analysis was restricted to the follow-up period occurring from 1 December 2001 to 30 November 2002.
The HIV/AIDS Drug Treatment Program (DTP) The British Columbia Centre for Excellence in HIV/AIDS supports the province-wide HIV/AIDS Drug Treatment Program (DTP) that distributes antiretro408
viral agents at no cost to eligible HIV-infected individuals, and
