title: High rates of transitions to injecting drug use among Mexican American non-injecting heroin users in San Antonio, Texas (never and former injectors).
abstract: OBJECTIVE
  To assess the incidence and rate of transition to injecting among Mexican American noninjecting heroin users.
  
  
  METHODS
  In a prospective cohort study of street-recruited MA-NIU in San Antonio, Texas, 2002-2005, participants were administered structured interviews and tested for Human immunodeficiency virus (HIV), hepatitis B virus (HBV) and hepatitis C virus (HCV). The analysis sample comprised former injection drug users (last injected >6 months ago, n=47) and those who had never injected drugs and tested HCV negative (n=219). A transition to injecting was defined as the first injection of illicit drugs since baseline interview. Transition rates were based on person-years at-risk (PYAR). Proportional hazards regression was used to estimate crude and adjusted (for significant differences between former and never injectors) hazard ratios and 95% confidence intervals of injecting history on transitioning to injecting.
  
  
  RESULTS
  Sixty-three (24%) participants transitioned to injecting at a rate of 22.3/100 PYAR (95% CI: 17.2-28.2). Former-injectors were significantly more likely to transition than never injectors (43% or 20/47 vs. 20% or 43/219; p<0.001), and did so at a faster rate (40.4/100 PYAR, 95% CI: 24.6-60.0 vs. 18.5/100 PYAR, 95% CI: 13.4-24.4), with the crude HR=1.931 (95% CI: 1.116, 3.341) and adjusted HR=2.263 (95% CI: 1.192-4.294).
  
  
  CONCLUSIONS
  The rate of transitioning to injecting was high and greater among former injectors. Of particular concern is the high rate of injecting initiation among never injectors. Future analyses will examine factors associated with injecting initiation, including individual susceptibility and behaviors, social networks, and the cultural and drug market context.
authors.affiliation: Graduate College of Social Work, Center for Drug & Social Policy Research, University of Houston, 110HA Social Work, Houston, TX 77204-4013, USA. avaldez2@uh.edu
authors.forename: Avelardo
authors.initials: A
authors.lastname: Valdez
authors.forename: Alan
authors.initials: A
authors.lastname: Neaigus
authors.forename: Charles
authors.initials: C
authors.lastname: Kaplan
authors.forename: Alice
authors.initials: A
authors.lastname: Cepeda
mesh_terms: D000293:Adolescent; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006556:Heroin Dependence / Q000208:ethnology* / Q000523:psychology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D017058:Mexican Americans / Q000208:ethnology* / Q000523:psychology*; D011446:Prospective Studies; D012307:Risk Factors; D015819:Substance Abuse, Intravenous / Q000208:ethnology* / Q000523:psychology*; D013781:Texas / Q000208:ethnology; D055815:Young Adult