Abstract

Risk factors associated with HIV incidence in homosexual and bisexual men followed in an open cohort study: Project Horizonte, Brazil (1994-2009)

M. Greco, A.P. Silva, D.B. Greco, M. Carneiro

Federal University of Minas Gerais/Project Horizonte, Belo Horizonte, Brazil

Background: Project Horizonte, a component of the Brazilian AIDS Vaccine Program, is an open cohort of homosexual/bisexual HIV negative men, established in Belo Horizonte, Brazil (Project Horizonte). Its objectives are to evaluate: seroincidence, risk factors for HIV infection, preventive measures and willingness to participate in vaccine trials. Volunteers are monitored biannually through psychosocial interviews and medical consultation. We describe the risk factors associated with HIV incidence in this cohort.
Methods: This is a nested case-control study where each newly HIV converted volunteer (case) was compared with three controls randomly selected among the HIV negative, matched by admission time and age. Variables were selected from psychosocial/epidemiological questionnaire collected at HIV seroconversion visit: demographic characteristics; sexual behavior; risk factors for HIV infection; knowledge about HIV/AIDS. Conditional logistic regression models were performed.
Results: Overall incidence rate was 2.2/100 persons-years. Among 1085 volunteers enrolled, 75 tested positive for HIV on follow-up and they were matched with 225 HIV negative controls. Mean age was 35 years, 62% were mullatos, 55% received less than 3 minimum wages. Univariate analysis showed that cases had higher number of occasional and unknown partners, had greater difficulty in negotiating condom use, reported higher frequency of condom rupture and alcohol using in sexual intercourse. After adjustments, risk factors were: unprotected receptive anal sex with occasional partners (OR=3.8; 95% CI 1.6-9-3); reporting that condoms interfere with sexual intercourse (OR=2.7; 95% CI 1.3-5.7); failure to seek information about HIV/AIDS (OR=4.4, 95% CI 1.7-11.8).
Conclusions: Despite the volunteers' regular clinical and pshycosocial follow-up with access to prevention information and condoms, some still engage in high risk practices. Therefore, it is necessary to better investigate the individual and social aspects that interfere with unsafe sexual practices.