Time trends in high-risk injection practices in a multi-site study in Massachusetts: effects of enrollment site and residence.

Time trends in needle sharing and bleach use were examined among needle users enrolled at drug abuse treatment and nontreatment sites in greater Worcester, MA, from 1987 through 1989. Substantial declines in high-risk behavior were found, with different trends at drug treatment versus nontreatment sites. The percentage of individuals sharing needles declined at treatment facilities but not at nontreatment sites. Among those sharing, the proportion using bleach increased at both drug treatment and nontreatment sites. The bleach distribution program in Worcester appears to be associated with increased bleach use among residents. Bleach use was associated with residence in Worcester, after controlling for age, gender, race, enrollment site, time period, and frequency of sharing. Risk reduction in the subpopulation of needle users entering treatment was greater than that among those not in treatment. As avoidance of sharing is likely to be more effective than bleaching for the prevention of human immunodeficiency virus (HIV) transmission, the subpopulation not in treatment should be targeted for prevention programs.