Interventions to encourage users of illicit injection drugs must take into consideration the social and geographic networks of users, is the conclusion of a paper co-authored by Dr. April Young, assistant professor of epidemiology at the University of Kentucky College of Public Health. The paper appears in the May edition of the American Journal of Epidemiology.

[Photo: Dr. April Young]

The study analysis uses social network and spatial data to examine associations between one’s injection status and social and/or spatial proximity to others who inject. Subjects were drawn from the rural Appalachian population, a group with significant rates of injection drug use.

503 rural persons who use drugs were recruited to participate in the Social Networks among Appalachian People (SNAP) Study (2008-2010). Interviewer-administered surveys collected information on recent sex, drug use, and social support network members (n = 897 ties).

Using network simulations, investigators determined a threshold for the association between social proximity to others who inject and recent injection status (‘socially proximal’ defined by shortest path≤2). They defined ‘geographically proximal’ as the median road-network distance between pairs of individuals who both injected (≤7 miles). Logistic regression was used to determine the independent and joint association between socially and geographically proximal injecting peers and one’s injection status.

After adjustment, the odds of recent injection increased by 0.4 percent for each injecting peer who was geographically but not socially proximal, 12 percent for each geographically and socially proximal injecting peer, and 22 percent for each injecting peer who was socially but not geographically proximal.

The investigators conclude that “network-based interventions which promote injection cessation should consider collecting sociometric network data to examine whether the intervention diffuses through the network and whether there are additive or threshold effects.”