Crack cocaine use hastens HIV disease progression, investigators report in the January 1st 2009 edition of the Journal of Acquired Immune Deficiency Syndromes. The research, which was conducted amongst drug users in Miami, found that crack cocaine users had poorer adherence to antiretroviral treatment. But this was only a partial explanation, as the investigators found that crack cocaine users who were taking anti-HIV drugs experienced both more rapid falls in their CD4 cell count and increases in their viral load.
It is estimated that 18% of all HIV infections in the US are due to injecting drug use. Injecting drug users with HIV often experience rapid HIV disease progression with almost 50% progressing to AIDS within a year of their HIV diagnosis.
Non-injecting drug use is also widespread amongst people with HIV and studies have yielded conflicting evidence about its impact on HIV disease progression. One study has, however, shown that crack-cocaine users experience a faster decline in CD4 cell count in the short term than non-users of this drug. Studies in HIV-positive women have shown that crack cocaine users have lower CD4 cell counts and have a greater risk of AIDS or death.
Drug use can mean that individuals have poorer adherence to their antiretroviral therapy. It can be difficult for investigators to show if poorer outcomes in drug users are due to non-adherence to HIV treatment or to the physiological effects of drug use.
Investigators therefore designed a study to try and determine the relationship between drug use and HIV disease progression, as shown by falls in CD4 cell count and increases in viral load, in the era of modern HIV treatment.
Their research involved 222 HIV-positive drug users who were recruited in Miami between 2002 and 2005. The study lasted 30 months. At six-monthly intervals, individuals had blood tests to measure their CD4 cell count and viral load. They were also interviewed about their medical history, including use of antiretroviral drugs and other medication. Individuals were also asked to complete a questionnaire detailing their use of alcohol, tobacco and illicit drugs.
Most of the patients (77%) were black and the mean age was 42 years. Baseline median CD4 cell count was 314 cells/mm3 with median viral load at this point being a little under 12,000 copies/ml. Antiretroviral therapy was being taken by 63% of patients on entry to the study.
The most commonly used drug was crack cocaine (50%), followed by cannabis (35%) and powder cocaine (14). Alcohol was consumed by 55% of patients.
On entry to the study, 130 patients had a CD4 cell count above 200 cells/mm3. The investigators assessed the impact of illicit drug use on falls in CD4 cell count over the 30 months of the study. Patients were classified as a drug “user” if they reported illicit substance use in the previous six months.
After controlling for baseline CD4 cell count and use of antiretroviral drugs, only use of crack cocaine was found to have an independent effect on decline in CD4 cell count, the use of this drug doubling the risk of CD4 cell count falling to below 200 cells/mm3 (hazard ratio [HR] = 2/15, 95% confidence interval [CI]: 1.08-4.25, p = 0.029).
The relationship between crack cocaine use and rapid loss of CD4 cell count remained unchanged when the investigators controlled for alcohol use (HR = 2.093, p = 0.041).
Next the investigators restricted their analysis to drug users who were not taking antiretroviral treatment. Once again, only crack cocaine was associated with an increased risk of a fall in CD4 cell count to below 200 cells/mm3 (HR = 3.9, 95% CI: 1.049-14.85, p = 0.042).
Many individuals reported the use of multiple substances, but only use of both crack and cannabis (HR = 2.42, 95% CI: 1.042 – 5.617, p = 0.04) was associated with an increased risk of CD4 cell count falling below 200 cells/mm3.
The researchers also found that crack cocaine use was a significant predictor of higher viral load (p = 0.019).
To evaluate the effect of illicit drug use on adherence, the investigators compared the proportion of patients with a viral load below 400 copies/ml according to the type of substance used. At every study visit, crack cocaine users were significantly less likely to have a viral load below this level than individuals who did not use this drug.
The investigators write that their findings "show a significant acceleration of decline of CD4 cell count to a level considered diagnostic for AIDS and elevated viral load in crack-cocaine users independent of reported [antiretroviral] use over 30-month duration.”
They add, “according to our data, crack-cocaine use has a multifactorial mode of action in which both direct effects of disease progression and reduced adherence to antiretroviral medication seem to be compounded to accelerate disease progression.”
The investigators conclude, “these findings make a strong case for the need for targeted interventions to curb crack-cocaine use and to reduce overall drug use in those who are infected with HIV to slow disease progression in people who use crack-cocaine.”