Infection with HIV is associated with a higher risk of death after an overdose amongst injecting drug users, according to a study conducted by investigators at Johns Hopkins University in Baltimore and published in the June 10th edition of AIDS. The investigators found that drug use behaviours, disease associated with HIV infection, and impaired liver function significantly contributed to the increased risk of death after an overdose.
“Among injecting drug users, two commonly reported causes of death include overdose, and in HIV epidemic areas, AIDS”, write the investigators. However, few studies have addressed the association between HIV and mortality from drug overdose, and the mechanisms associated with overdose deaths in HIV-positive individuals are unclear.
Investigators from Johns Hopkins University wished to explore the effect of HIV infection on the risk of overdose mortality amongst 1927 active injecting drug users who were prospectively followed from 1988 to 2001. Overdose mortality was compared between injecting drug users who became HIV-positive and those who remained HIV-negative.
All individuals had used injecting drugs within six months of their recruitment to the study. During the follow-up a total of 308 individuals HIV seroconverted. Predictors of seroconversion included younger age at baseline, younger age of initiation of drug use, and sex between men (p
A total of 13,871 person years of follow-up were available for analysis by the investigators. There were a total of 92 validated deaths due to overdose, of which 69 were amongst HIV-positive individuals. Although the overall mortality rate from overdose was 7/1000 person years, it was significantly lower amongst HIV-negative injecting drug users at 6/1000 person years than HIV-positive injecting drug users at 14/1000 person years (p
The investigators calculated the hazard ratio for overdose death amongst HIV-positive injecting drug users, adjusting for potential confounders including demographics, injecting drug use behaviours, alcohol abuse, substance misuse treatment and sexual orientation. The adjusted harzard ratio was 2.06.
In further analysis, the investigators used a marginal structural Cox regression model to estimate the total effect of HIV infection on overdose mortality. Adjusting for drug use behaviours, alcohol use, medical conditions and access to healthcare, the association between HIV and overdose mortality was 30%.
Adjustment was also made for liver function. When abnormal liver function was included in the extended marginal structural model, the association between HIV infection and overdose death was 35%. In addition, the investigators found that when they adjusted for drug and alcohol use, drug abuse treatment, employment, medical conditions, and health insurance, they found that abnormal liver function was associated with a significantly increased risk of death after overdose (hazard ratio 2.0; p = 0.04).
“The major finding of this study was the observation of a higher rate of overdose mortality among individuals with HIV infection”, write the investigators. They add, “factors accounting for approximately 35% of the association between HIV infection and overdose death included a combination of drug use behaviour, medical conditions, healthcare utilisation and abnormal liver function.”
“Special attention about overdose prevention should be directed to individuals with HIV infection who use illicit drugs”, conclude the investigators.
Wang C et al. The effect of HIV infection on overdose mortality. AIDS 19: 935 – 942, 2005.