Daily alcohol use as an independent risk factor for HIV seroconversion among people who inject drugs

To estimate the relationship between daily alcohol use and HIV seroconversion among people who inject drugs (PWID) in a Canadian setting.

Data from an open prospective cohort study of PWID in Vancouver, Canada, recruited via snowball sampling and street outreach between May 1996 and November 2013. An interviewer-administered questionnaire including standardized behavioural assessment and HIV antibody testing were conducted semi-annually. Baseline HIV-seronegative participants completing ≥ 1 follow-up visits were eligible for the present analysis.

A total of 1683 eligible participants, were followed for a median of 79.8 [interquartile range (IQR) = 33.3-119.1] months.

The primary end-point was time to HIV seroconversion, with the date of HIV seroconversion estimated as the mid-point between the last negative and the first positive antibody test results. The primary explanatory variable was self-reported daily alcohol use in the previous 6 months assessed semiannually. Other covariates considered included demographic, behavioural, social/structural and environmental risk factors for HIV infection among PWID (e.g. daily cocaine injection, methadone use, etc.).

Of 1683 PWID, there were 176 HIV seroconversions during follow-up with an incidence density of 1.5 [95% confidence interval (CI) = 1.3-1.7] cases per 100 person-years. At baseline, 339 (20.1%) consumed alcohol at least daily in the previous 6 months. In multivariable extended Cox regression analyses, daily alcohol use remained associated independently with HIV seroconversion (adjusted hazard ratio: 1.48; 95% CI = 1.00-2.17).

Daily alcohol use appears to be an independent risk factor for HIV seroconversion among our cohort of PWID.