Theme: Epidemiology & Public Health Research Year: 2024
Background: Sharing of syringes and injecting equipment among people who inject drugs (PWID) persists with 50-70% recently sharing, posing significant risks for HIV and HCV transmission. Up until recently studies considering the role of interpersonal factors (e.g., the interactions and personal relationships between individuals) on transmission have been limited by the quality of measures to examine interpersonal dimensions of risk. This study aims to assess injecting-related interpersonal factors within injecting partnerships and their associations with high-risk injecting behaviors.
Methods: From 2015-2019, PWID and their primary injecting partners in Montreal, Canada, and San Francisco, USA, underwent HCV screening and separately completed questionnaires including a validated measure of injecting-related interpersonal factors (trust, intimacy, cooperation, power, and risk perception). Using Actor-Partner Interdependence Models, we estimated actor and partner effects of injecting-related interpersonal factors on equipment and needle sharing and assessed the moderating influence of partnership composition (age, gender, HIV/HCV serostatus.
Results: Among 180 PWID (136 dyads), median age was 30 and 74% were male, 21% were non-white, and 49% had HCV infection. Overall, 68% and 18% reported equipment and needle sharing, respectively. Actor’s risk perception (RR=0.89, 95%CI: 0.85-0.92) and partner’s cooperation (RR=1.10, 95%CI: 1.09-1.12) were associated with actor’s equipment sharing. While actor’s and partner’s power were negatively associated to actor’s equipment sharing (RR=0.81, 95%CI: 0.80-0.83 and RR=0.93, 95%CI:0.91-0.95, respectively). Trust was positively associated with actor’s equipment sharing for both actors and partners (RR=1.07, 95%CI: 1.03-1.10, RR=1.20, 95%CI: 1.16-1.24, respectively). We observed similar findings for needle sharing. Partnership composition moderated the relationship between interpersonal factors and equipment sharing for intimacy, cooperation, and risk.
Conclusion: Findings highlight the positive association of trust and cooperation with equipment sharing, while power dynamics were negatively linked to such behaviors. These insights underscore the importance of tailored interventions addressing both individual and relational factors to mitigate blood-borne infection transmission within this vulnerable population.