Injection Drug Use, Unemployment, and Severe Food Insecurity Among HIV-HCV Co-Infected Individuals: A Mediation Analysis

Abstract

Severe food insecurity (FI), which indicates reduced food intake, is common among HIV-hepatitis C virus (HCV) co-infected individuals. Given the importance of unemployment as a proximal risk factor for FI, this mediation analysis examines a potential mechanism through which injection drug use (IDU) is associated with severe FI. We used biannual data from the Canadian Co-infection Cohort (N = 429 with 3 study visits, 2012-2015). IDU in the past 6 months (exposure) and current unemployment (mediator) were self-reported. Severe FI in the following 6 months (outcome) was measured using the Household Food Security Survey Module. An overall association and a controlled direct effect were estimated using marginal structural models. Among participants, 32% engaged in IDU, 78% were unemployed, and 29% experienced severe FI. After adjustment for confounding and addressing censoring through weighting, the overall association (through all potential pathways) between IDU and severe FI was: risk ratio (RR) = 1.69 (95% confidence interval [CI] = 1.15-2.48). The controlled direct effect (the association through all potential pathways except that of unemployment) was: RR = 1.65 (95% CI = 1.08-2.53). We found evidence of an overall association between IDU and severe FI and estimated a controlled direct effect that is suggestive of pathways from IDU to severe FI that are not mediated by unemployment. Specifically, an overall association and a controlled direct effect that are similar in magnitude suggests that the potential impact of IDU on unemployment is not the primary mechanism through which IDU is associated with severe FI. Therefore, while further research is required to understand the mechanisms linking IDU and severe FI, the strong overall association suggests that reductions in IDU may mitigate severe FI in this vulnerable subset of the HIV-positive population.

Association between household food insecurity and mortality in Canada: a population-based retrospective cohort study

“…Given the prevalence of deaths related to drug poisoning in our sample (results not shown), our finding on unintentional injuries may partly reflect the link between food insecurity and substance use, 49,50 which is often complicated by the coexistence of HIV infec tion and depression. [51][52][53] The higher risk of death from suicides is consistent with Canadian studies documenting links between food insecurity and suicidal ideation and attempts. [19][20][21] Suicide preven tion needs to be prioritized for adults experiencing food insecurity.…”

Which is the cart and which is the horse? Getting more out of cross-sectional epidemiological studies

“…However, even in the absence of repeated measurements on participants, regression analyses typically generate more meaningful estimates if there is at least a hypothesized temporality of the relationships under examination (3,4,7) . In our papers, we concluded that a hypothetical intervention on IDU may potentially reduce FI (10,11) . While this conclusion was contingent upon several assumptions (e.g.…”

“…After an examination of the relevant literature (13) , we decided to focus our attention on IDU as an exposure variable and FI as a potential consequence of this behaviour. We conceptualized this analysis (10) , in time, using a directed acyclic graph, which is a visual representation of the hypothetical relationship between variables (7,14) . Unlike the cross-sectional study by Patil et al (8) , we benefited from the use longitudinal cohort data, which allowed us to temporally order the exposure (IDU) and outcome (FI) measures in our data set through variable lagging (10,11) .…”

“…We conceptualized this analysis (10) , in time, using a directed acyclic graph, which is a visual representation of the hypothetical relationship between variables (7,14) . Unlike the cross-sectional study by Patil et al (8) , we benefited from the use longitudinal cohort data, which allowed us to temporally order the exposure (IDU) and outcome (FI) measures in our data set through variable lagging (10,11) . However, even in the absence of repeated measurements on participants, regression analyses typically generate more meaningful estimates if there is at least a hypothesized temporality of the relationships under examination (3,4,7) .…”

“…In our own work, we have documented the prevalence of FI and examined the relationship between injection drug use (IDU) and FI among people living with HIV–hepatitis C virus co-infection in Canada ( 10 , 11 ) . We considered past research which had suggested that the relationship between IDU and FI was bidirectional ( 12 ) , whereby IDU may impact FI and FI may also be a risk factor for IDU.…”