Sharing of injection equipment among 3755 intravenous drug users in Valencia, Spain, 1987-1992.

Background: In order to identify, in a sample of heroin intravenous drug users (IVDU), those factors associated with the predominant risk behaviour related to the transmission of HIV-1 infection--sharing of injection equipment--a cross-sectional survey was carried out in Valencia, Spain from 1987 to 1992.
Methods: Informed consent and pertinent data were obtained from 3755 heroin IVDU recruited at two public AIDS Information Centres in two cities in the region of Valencia. Data were gathered on sociodemographic variables, and sexual and drug use behaviour by interview. The subjects were subsequently tested for HIV-1 antibody. A univariate analysis was carried out to identify variables that were significantly associated with sharing injection equipment. A logistic regression model was used to control for possible confounders.
Results: The IVDU who were teenagers, prostitutes (OR = 1.95), who had antibodies to HIV-1 (OR = 1.30) or who had an IVDU steady partner were at significantly higher risk for sharing of injection equipment. Higher levels of education, condom use (OR = 0.65) and living in the smaller city (OR = 0.75) were inversely related to sharing injection equipment.
Conclusions: Our results suggest that different subgroups of IVDU have different characteristics that place them at different risk for HIV-1 infection. These characteristics should guide the design and intensity of specific preventive interventions. Teenagers and IVDU with low educational levels should be targetted for special attention by health authorities.