The impact of zidovudine on dementia-free survival in a population of HIV-positive men and women on antiretroviral therapy

Our objective was to characterize the effect of zidovudine therapy on AIDS dementia complex (dementia) free survival among HIV-infected men and women in a population-based cohort with free access to antiretroviral therapy in the province of British Columbia. Time to diagnosis of dementia among individuals was examined on the basis of zidovudine duration, CD4+ cell count at first treatment, gender, and transmission group [men having sex with men (MSM), intravenous drug users (IDU), heterosexuals]. We restricted the analysis to subjects with CD4+ cells counts within 12 months prior to treatment start date. Among 641 participants eligible for analysis, median duration of follow-up was 3.6 years, under which 86 (9.3%) events of dementia occurred. Participants were less likely to develop dementia with: increased zidovudine exposure (OR=0.26, 95% CI: 0.14-0.49), at least 260 CD4+ cells/mm(3) (median) (OR=0.52, 95% CI: 0.34-0.78), and MSM risk group (OR=0.57, 95% CI: 0.35-0.94). Those infected through heterosexual contact had an increased risk (RR=2.04, 95% CI: 1.02-4.07). Using Cox's proportional hazards model, controlling for CD4+ cell count at treatment start date, independent predictors of dementia-free survival were: duration of zidovudine (OR=0.28, 95% CI: 0.15-0.52) and MSM transmission group (OR=0.61, 95% CI: 0.37-1.00). In this observational treatment cohort, factors associated with dementia-free survival include duration of zidovudine (AZT) therapy and MSM transmission group. It is not clear from these data whether the AZT protective effect is exclusive to this agent or whether other therapies might offer a similar protective effect.