Of the 2,599 individuals reporting injecting drugs in the past 6 months, 41% were White, 45% were Black, and 14% were Latino. The mean age was 39 years and ranged from 18 to 75 years. Seventy-five percent of the sample was male and 68% reported having a high school diploma or equivalent. Just over half (54%) reported having a primary sex partner. For outcome variables, 54% reported injecting in a private residence at their last injection, while 34% reported injecting in public venues and 12% attended a shooting gallery. Thirty-seven percent of the sample regularly used SEPs as their usual source for syringes. Thirty-four percent reported receptive syringe sharing and 44% had used water, cotton, or cookers after someone else.
shows mean distances (miles) between location pairs for the total sample and by race. When place of residence is included in the location pair, we see that distances traveled for Whites to buy (F2,1635=47.89, p<0.000) and use (F2,1562=24.69, p<0.000) drugs, and access SEPs (F2,1775=81.61, p<0.000), is on average twice the distance traveled for Blacks and Latinos. Thus, Blacks and Latinos live closer to where they buy and use drugs than do Whites. The distance between where drugs are bought and used is a relatively short distance for all race groups. Finally, SEPs in Philadelphia appear to be very appropriately placed. They are less than 1 mile away from drug purchasing locations and an average of 1.6 miles from injection drug use locations.
Two-point Manhattan Distances in Miles (Kilometers) by Race, Philadelphia, PA, USA, 2002-2006. (* P < 0.05)
Race, Distance and Place of Last Injection
We fit models examining the effects of two distances on place of last injection—the path from home to buy location to use location, “pathhbu,” and the average distance among these same locations. shows results from the two models with pathhbu as the primary predictor of injecting in a shooting gallery, public venue, or private residence (reference). No significant associations were observed between path distance and shooting gallery use, between race and shooting gallery use, nor between a distance by race interaction term and shooting gallery use. Blacks, however, were significantly less likely than Whites to inject in public places as path distance increased (OR=0.94, CI: 0.90-0.98). We fit a similar model using average distance, rather than path, and with a few exceptions, observed similar results. The effects of average distances were in the same direction, but greater in magnitude than those of pathhbu.
Multinomial Regression Results: Main and Interaction Effects of Path Distance (Miles) and Race on Place of Last Injection, Philadelphia, PA, USA, 2002-2006 (N=1,443)
Race, Distance and Regular Syringe Source
shows the associations of distances between the nearest SEP site and home, buy, and use locations, race and regular source of syringes. All models test the main and multiplicative effects of race and distance on the regular use of non-SEP sources. The three models differ with respect to the distance measure used. Model I uses the distance between the nearest SEP site and injectors’ homes (SEP-home); Model II uses the distance between the nearest SEP site and drug buy location (SEP-buy); and Model III uses the distance between the nearest SEP site and use location (SEP-use). Each model adjusts for age, gender, education, and partner status. The most common non-SEP sources used were “works sellers” (34%), friends (11%), diabetics (11%), and [drug] dealers and other users (8%). In Model I, because there were no significant interaction effects, we interpret the main effects of race and distance as independent effects. We found that for each mile of increased distance between SEP and IDUs homes increased, there was a 6% increased likelihood of using non-SEP sources for syringe access. In this same model, results show that both Blacks (OR=1.65, CI: 1.22-2.25) and Latinos (OR=1.57, CI: 1.03-2.39) were significantly more likely than Whites to access syringes from sources other than SEPs. In Models 2 and 3, we found evidence for significant interactions with distance for Latinos, but not Blacks. As distances increased, Latinos were more likely to use non-SEP sources to access syringes; distance did not affect where Blacks acquired syringes. In both Models 2 and 3, we find that the greater the distance between SEP and buy (OR=6.70, CI: 2.32, 19.4) and use locations (OR=5.35, CI: 2.53, 11.3), Latinos were much more likely than Whites to access syringes from non-SEP sources.
Logistic Regression Results: Main and Interaction Effects of Path Distance (Miles) and Race on Regular Use of non -SEP Sources for Syringes, Philadelphia, PA, USA, 2002 -2006
Race, Distance and Receptive Sharing of Injection Equipment
Results on the effects of distance on receptive sharing are displayed in . For these models, we used the average distance among all four injection-related sites--SEP, home, buy, and use locations. We also fit models using path distances that yielded similar results. We examined the effect of average distance on 1) receptive syringe sharing and 2) using water, cookers, and cotton after someone. Similar to our results for regular source of syringes, we observed significant interaction effects for Latinos, but not for Blacks. Main effects for Blacks indicate that they were the least likely group to use needles (OR=0.27, CI: 0.19-0.38) or other injection equipment (OR=0.37, CI: 0.27-0.52) after someone else, an effect not moderated by distance. Latinos’ use of injection equipment (needles, water, cooker, cotton), however, was moderated by distance, showing that their odds of using a needle or other works after someone else increased by 21% and 24%, respectively, with each mile increase in average distance among the four locations. Results also showed increased odds of receptive syringe sharing after a partner, relative, or friend (OR=1.94, CI: 1.51-2.50) and other non-kin, non-friend users (OR=1.59, CI: 1.10-2.31). With regard to the sharing of rinse water, cooker, and cotton, individuals were more than twice as likely to use these after a partner, relative or friend (OR=2.18, CI: 1.73-2.73), but not with “other” users. Regular use of non-SEP sources of syringes increased the odds of receptive syringe sharing by 60%, but had no effect on using water, cooker, and cotton after someone.
Ordinal Regression Results: Main and Interaction Effects of Average Distance (Miles) and Race on Receptive Syringe Sharing, Philadelphia, PA , USA , 2002-2006