Risk behaviour change and HIV infection among injection drug users in Montreal

Objective: To investigate the independent association between changes in ri sk behaviour and HIV seroconversion risk among Montreal injection drug user s (IDU). Design: A longitudinal study of risk behaviour change and the maintenance o f low-risk practices. At baseline and semi-annually, subjects were tested f or HIV, and questionnaires on risk behaviour were completed. Results: A total of 833 IDU were recruited from January 1992 to June 1998, and completed a minimum of three visits. Large fluctuations in risk behavio ur were observed, and the risk of HIV infection appeared to be dependent up on the consistency of risk behaviour practised. IDU who consistently engage d in risky behaviour were at high risk of HIV infection. IDU who attempted to practise low-risk behaviour but experienced relapses to risky behaviour were also at considerable risk of infection. IDU who managed to maintain lo w-risk practices were at minimal risk. Using Cox regression analysis, the h azard ratio (HR) of HIV seroconversion among IDU who consistently and incon sistently shared needles with an HIV-positive partner was 8.17 (95% CI 3.59 -18.59) and 2.63 (95% CI 1.33-5.17), respectively, relative to non-needle s harers. Corresponding HIV incidence rates were 30.42 per 100 person-years ( py) among consistent sharers, 13.78 per 100 py among inconsistent sharers a nd 2.51 per 100 py among non-sharers. Conclusion: Although some HIV risk reduction was evident, behaviour change seems to be effective only in IDU who adopt and maintain How-risk practices . Additional strategies may be needed to assist IDU in the maintenance of l ow-risk practices. (C) 2000 Lippincott Williams & Wilkins.