Title: Blood borne infections and duration of injection drug use among young, newly initiated injection drug users
Description: The purpose of this research is to examine select baseline characteristics and drug use and sexual behaviors by duration of injection drug use among young, newly initiated injection drug users (IDUs) to better understand factors associated with risk of infection during the early stage of an injection drug users' career. This research was conducted using questionnaire data from the Collaborative Injection Drug Users Study II (CIDUS-II), a CDC-sponsored prospective study of young (18-29) and/or newly initiated IDUs (duration of injection < 6 years). The study was conducted at six sites in five United States' urban areas: Baltimore, Chicago, Los Angeles, New Orleans, and New York City (Harlem and the Lower East Side). Investigators conducted interviews to assess baseline characteristics and injection drug use and sexual risk factors and obtained serum for testing of bloodborne infections including Hepatitis C (HCV). Duration of injection was calculated from the age of first injection to age at the time of the interview and roughly divided into tertiles by duration while maintaining years as whole numbers: 0-1 year, 2-3 years, and 4-6 years.

Among the 1836 participants included in the analysis, 34% (n = 619) had been injecting for 0-1 year, 38% (n = 697) for 2-3 years, and 28% (n = 520) for 4-6 years. Overall HCV prevalence was 34%. By duration of injection, HCV prevalence differed by site of recruitment. In Baltimore for blacks HCV prevalence increased from 33.3% among IDUs injecting <2 years to 79% among IDUs injecting 4-6 years. HCV prevalence in other cities (Chicago, Los Angeles, New Orleans and New York) showed less difference by duration. By racial and ethnic group, HCV prevalence was higher in blacks than non-blacks (=80% white) in all cities (OR = 1.43, 95% CI: 1.00 - 2.05) except Baltimore where prevalence was higher in whites (OR = 5.20, 95% CI: 2.94 - 9.18) than blacks (OR = 2.52, 95% CI: 1.38 - 3.07) as compared to whites in all other cities. The IDU groups of <2 years duration (n = 691) and 2-3 years duration (n = 697) had higher odds than the 4-6 year group (n = 520) of reporting injecting with others (Odds Ratio, OR = 1.52, and OR = 1.47, respectively) and injecting on average more now (OR = 1.44 and OR = 1.44, respectively).

The associations remained after multivariate adjustment for demographic variables. In addition, the frequency of several other important risky injection practices were found to be higher among more newly initiated including indirect sharing (sharing of cookers, cotton and rinse water) and backloading, and certain preventive behaviors was found to be lower among this group as well, including use of new needles and NEPs. Duration of injection did not appear to be associated with sexual risk behaviors such as giving or receiving sex for money or drugs or frequency of condom use with sex partners. These data confirm high prevalence of HCV soon after initiation of injection, and increases in HCV prevalence by duration of injection that differed across U.S. cities and by racial/ethnic group. In addition, these data provide support to the ongoing discussions about increased risk among young, newly initiated injection drug users, with risky injection practices higher among more newly initiated IDUs.

These findings help to improve our understanding about the periods of increased risk and provide important information about certain baseline characteristics and injection practices among young, newly initiated IDUs -- essential data to consider when developing risk reduction programs.