Changes in HIV/AIDS risk behaviors in drug users in St. Louis: Applications of random regression models

A National Institute on Drug Abuse demonstration project in AIDS prevention among drug users was conducted in St. Louis during the years 1990 through 1994. The main objective was to reduce the spread of HIY by counseling drug users and by improving drug-treatment programs in the area. A second objective was to examine the correlates of risk behavior. A structured interview was administered six times over an 18-month period Of those persons assessed at baseline (n=475), 95.0% (n=451) were also reinterviewed in the last interview at 18 months. Both group and individual level changes in risk behavior were assessed using random regression models. We report on three potential risk behaviors for HIV/AIDS: (1) number of sexual partners, (2) frequency of condom use, and (3) injection drug use. For each risk behavior a separate statistical model was estimated. The results of the random regression models showed significant reductions in number of sexual partners and injection drug use. Additionally a number of variables, such as perceived risk for AIDS and knowledge of HIV/AIDS, were statistically significantly covariates of risk behavior.