| 301 |
RISK FACTORS FOR HIV AMONG FEMALE AND MALE INJECTION DRUG USERS: DOES SEXUAL TRANSMISSION EXPLAIN WHY FEMALE IDUS ARE BEING DISPROPORTIONATELY AFFECTED BY HIV IN VANCOUVER?
PM Spittal, M Tyndall, K Li, N Laliberte, E Wood, K Craib, MV O’Shaughnessy, MT Schechter
Vancouver Injection Drug Study, British Columbia Centre for Excellence in HIV/AIDS, St Paul’s Hospital; University of British Columbia
Objectives: Vancouver has experienced an explosive HIV epidemic among injection drug users. It was earlier reported that the HIV prevalence among women in this setting was higher than men. Follow-up of this cohort now allows an investigation aimed at identifying the constellation of risk factors among female IDUs that may explain the higher HIV risk.
Methods: The Vancouver Injection Drug User Study is a prospective cohort of over 1400 IDUs that began in 1996. In order to evaluate variables associated with seroconversion among men and women separately, two concurrent case-control studies of male and female seroconverters respectively were performed.
Results: Between May 1996 and December 2000, the seroconversion rate was higher among females than males (17% vs 11%; p=0.057). Among men, cases were significantly more likely than seronegative male controls to report borrowing needles (p=0.001), as well as frequent cocaine injection (p=0.001). In contrast, women seroconverters were more likely than seronegative female controls to report sexual risk behaviour (p=0.044), crack cocaine use (p=0.067), and frequent heroin injection (p=0.054). Tests for heterogeneity demonstrated that rates of needle borrowing (p=0.033) and sexual risk (p=0.033) were significantly different between genders. The multivariate analysis found significant gender interactions with regards to borrowing needles (OR=4.7 in men versus 1.3 in women) and frequent heroin use (OR=0.8 in men versus 2.0 in women).
Conclusions: This study confirms that HIV incidence is higher among female than male IDUs in our setting, a finding that has not been previously described. Furthermore, there are distinct differences regarding HIV risk factors between women and men. Whereas the epidemic in men appears to be cocaine-driven, there is strong evidence that sexual transmission and heroin-related risk may explain the elevated incidence of HIV among female IDUs.