The syndemic of incarceration, violence victimisation, needle/syringe sharing, & HIV infection: A population-based study of men who inject drugs in India

Materials & Methods

This was a secondary analysis of data obtained from a population-based, cross-sectional survey conducted during 2014/15 among men who inject drugs as part of the NACO’s Integrated Bio-Behavioural Surveillance (IBBS) study¹, which aimed to better understand HIV risk behaviours among key populations, with the goal of informing intervention efforts.

Analysis

The analyses followed directly from the conceptual considerations reviewed above, but the specific analytic plan was not preregistered. Given the complex survey design, we used the svyset command in Stata²⁹. No data were missing for HIV status or needle/syringe sharing. The exposures of violence victimisation and incarceration variables had 0.06 per cent and 1.91 per cent missingness, respectively. Given the small percentage of missing data, case-wise deletion was used.

To examine the model of synergistically interacting epidemics, we included product terms in the regression models to assess for two- and three-way interactions. This was done on both the additive and multiplicative scales³⁰, between three key variables, namely, past-year violence victimisation (yes/no), past-year incarceration experience (yes/no), and needle/syringe sharing during the previous episode of injection drug use (yes/no). The dichotomous outcome measure was HIV-positive status (yes/no). Regression models included covariates such as age, education, marital status, inconsistent condom use, HIV knowledge, and HIV programme exposure (Supplementary material 1).

Supplementary material 1

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To evaluate the model of serially causal epidemics, we conducted a mediation (path model) analysis (Figure) using MPlus (version 7.2)³¹. For this analysis, we specified needle/syringe sharing as a continuous variable ranging from 0 to 2, and the other two exposure variables (incarceration experience and severe violence victimisation) and the outcome variable (HIV status) as binary measures. Given that incarceration experience and violence victimisation are associated with HIV risk^8,12,19, we tested the extent to which the associations between incarceration experience and HIV status, and between violence victimisation and HIV status, were mediated through needle/syringe sharing. We estimated the bias-corrected confidence intervals of the direct, indirect, and total effects with 2000 bootstrap samples.

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Figure.

Path model linking incarceration experience, violence victimisation, needle/syringe sharing, and HIV-positive status.

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Results

The participants’ median age in this study was 29 yr, 45.6 per cent were currently married, and the median of education was standard 9 (range: 0 to 16) (Supplementary Table I). The weighted average national HIV prevalence among men who inject drugs was 9.9 per cent [95% confidence interval (CI), 9.0% to 10.9%]. Past-year incarceration was reported by 1,998 (10.2%) participants; among them, 568 (28.4%) reported having injected drugs within prisons, consistent with available knowledge about how drugs are readily accessible within prisons^17,22. Physical violence was reported by 6,915 (34.7%) participants. Among these, the reported violence was perpetrated by family members (40%; 2,766), strangers (33.1%; 2,351), fellow men who inject drugs (28.2%; 1,954), police (13.0%; 901), and goondas (thugs) (11.4%; 686).

Discussion

Using a probability-based cross-sectional survey data of 19,902 men who inject drugs in India, it was found that incarceration experience, violence victimisation, and needle/syringe sharing frequently co-occurred, and that needle/syringe sharing had a robust, a significant association with the HIV-positive status. We assessed two models of co-occurring epidemics²⁵, namely, synergistically interacting epidemics model, in which the combined effects of incarceration experience, severe violence victimisation, and needle/syringe sharing on HIV status were examined on both the additive as well as multiplicative scales, and a serially causal epidemics model, in which needle/syringe sharing was tested as a potential mediator of the effect of both incarceration experience as well as severe violence victimisation. On both multiplicative as well as additive scales, evidence for a synergistic three-way interaction between incarceration experience, severe violence victimisation, and needle/syringe sharing was found. However, on the multiplicative scale, evidence of synergistic two-way interactions between severe violence victimisation, and needle/syringe sharing was found. It is important to note that while this subgroup of individuals subjected to all three exposures should be considered extremely vulnerable, this subgroup represented only 0.3 per cent of all men who inject drugs sampled in the study. In testing the model of serially causal epidemics, the significant indirect effects of both incarceration experience and severe violence victimisation on HIV status through needle/syringe sharing were estimated. However, there were no significant direct or total effects of incarceration or violence victimisation on HIV status. Thus, the evidence of synergistically interacting epidemics model was strong but less strong for the model of serially causal epidemics.

The synergistic interactions between incarceration experience, violence victimisation, and needle/syringe sharing found in this study are consistent with existing research¹⁸. Studies from India have shown that injection drug use is prevalent within prisons, where clean needles/syringes are lacking, which may facilitate needle/syringe sharing^16,19 and, in turn, increase the risk of HIV infection⁹. The World Health Organization recommends a package of interventions, including needle/syringe programmes in prisons and in other closed settings³². Recently, NACO has begun to support HIV prevention intervention projects in prisons, but without needle/syringe exchange programmes^33,34. As noted earlier, physical violence victimisation may increase the risk for HIV infection by decreasing psychological well-being and/or the ability to protect oneself from infection, in turn leading to needle/syringe sharing and restricted access to HIV prevention and treatment services^15,19. Most studies of interpersonal violence have focused on the role of intimate partner violence and sexual violence on HIV-related risk behaviours³⁵. Given the lack of specific data on sexual violence against men who inject drugs in this dataset, we could not include sexual violence as part of the violence victimisation exposure variable.

Most studies exploring syndemics among PWID have assessed depression^6,7, intimate partner violence (particularly among women who use drugs)⁷, sexual risk behaviours⁷, and needle/syringe sharing³⁶ as exposures or outcomes. None of the studies of syndemics among PWID have focused directly on incarceration experience and HIV infection. Further, only a few studies among PWID have used appropriate statistical methods for assessing synergism³⁶. None have tested multiple models of co-occurring risks.

Our study has several limitations and strengths that warrant consideration (Supplementary material 2). Key limitations include the cross-sectional design precluding causal inferences, potential underreporting of incarceration due to social desirability bias, inability to directly compare non-nested models, and exclusion of women who inject drugs. Notable strengths include being the largest probability-based syndemic study among PWID to date and the use of appropriate statistical methods for assessing interactions. Despite using 2014/15 data, this study remains relevant by providing a baseline for understanding syndemic processes among PWID in India and identifying key gaps that persist in current interventions.

The study findings indicate that needle/syringe sharing independently, and in concert with incarceration experience and violence victimisation synergistically, increases the risk of HIV infection. This suggests that interventions targeting even one or two of these three exposures could potentially reduce HIV risk. However, integrated, multicomponent interventions addressing all these exposures, given the interconnections between these three exposures (as revealed in the serially causal model), could be more effective in reducing HIV risk. For exposures that lead to other exposures (e.g., incarceration leading to needle/syringe sharing), multi-level interventions might be more effective. For example, at the prison level - HIV prevention and substance use prevention and care interventions, such as screening and treatment of substance use disorders, provision of clean needles/syringes, naloxone for overdose, opioid substitution therapy, post-release employment, and mental health support, and actively linking recently-released men who inject drugs with HIV prevention services⁸; and at the individual level - screening and management of violence victimisation or its mental health consequences.

Overall, our research provides empirical evidence to suggest that there is a syndemic of violence victimization, incarceration experience, and needle/syringe sharing among men who inject drugs in India that amplifies their risk of HIV. Synergistic (additive and multiplicative) interactions were found between violence victimisation, incarceration experience, and needle/syringe sharing on HIV-positive status. Evidence for the model of serially causal epidemics suggests that preventing violence victimisation could potentially reduce needle/syringe sharing, thereby decreasing HIV transmission. Future studies should focus on gathering empirical evidence demonstrating the extent to which large-scale social and structural forces give rise to syndemics. These studies could adopt longitudinal mixed methods approaches and employ multi-level analyses, to elucidate interactions between various adverse psychosocial exposures. Such an understanding of the production and nature of syndemics will further contribute to both theory and program design and implementation.