Individual, study, and neighborhood level characteristics associated with peer recruitment of young illicit drug users in New York City: optimizing respondent driven sampling.

Recruiting a representative sample using respondent driven sampling (RDS) relies on successful peer recruitment. While prior studies have identified individual-level characteristics associated with peer recruitment, study- and neighborhood-level factors may also influence peer recruitment. This analysis aimed to identify individual-, study-, and neighborhood-level factors associated with RDS peer recruitment. 390 young adult (18-40 years) heroin, crack and/or cocaine users in New York City (NYC) were recruited via RDS into a cohort study aiming to identify social risk factors for transitioning from non-injection to injection drug use (2006-2009). Individual-level baseline characteristics (demographics, drug use, and network characteristics) and study factors (number of recruitment coupons received and participant attendance at RDS training sessions (RDST) on peer recruitment) were ascertained. Aggregate measures of neighborhood attitudes about drug use, drug users, and HIV were obtained from a separate anonymous NYC resident random-digit-dialing survey (2002) and linked with baseline data by zip code. Descriptive statistics and multilevel modeling were used to identify factors associated with peer recruitment. After adjustment, recruiting each additional eligible peer recruit was associated with receiving additional recruitment coupons, RDST attendance, and a greater proportion of community residents in one's recruitment neighborhood believing that clean needles should be made available to IDUs; heroin use was negatively associated with recruiting additional eligible peers. After adjustment, recruiting each additional peer (regardless of eligibility) was associated with receiving additional recruitment coupons and RDST attendance. Our data highlight the importance of neighborhood factors and suggest that RDS may not be as effective in areas characterized by negative attitudes about drug use. Group-facilitated recruitment training sessions may help counter negative social norms when implementing RDS in drug user studies.