Residential segregation and injection drug use prevalence among Black adults in US metropolitan areas.

OBJECTIVES: We analyzed the relations of two 1990 dimensions of racial residential segregation (isolation and concentration) with 1998 injection drug use prevalence among Black adult residents of 93 large US metropolitan statistical areas (MSAs).
METHODS: We estimated injection drug use prevalence among Black adults in each MSA by analyzing 3 databases documenting injection drug users' encounters with the health care system. Multiple linear regression methods were used to investigate the relationship of isolation and concentration to the natural logarithm of Black adult injection drug use prevalence, controlling for possible confounders.
RESULTS: The median injection drug use prevalence was 1983 per 100000 Black adults (interquartile range: 1422 to 2759 per 100000). The median isolation index was 0.48 (range: 0.05 to 0.84): in half the MSAs studied, the average Black resident inhabited a census tract where 48% or more of the residents were Black. The multiple regression model indicates that an increase of 0.50 in the isolation index was associated with a 23% increase in injection drug use prevalence among Black adults. Concentration was unrelated to the outcome.
CONCLUSIONS: Residential isolation is positively related to Black injection drug use prevalence in MSAs. Research into the pathways linking isolation to injection drug use is needed.