Use of the recreational drugs, cannabis, cocaine, poppers, or amphetamines, does not adversely affect the number or percentage of CD4 or CD8 cells in either HIV-positive or HIV-negative gay men, according to data from the Multicenter AIDS Cohort Study (MACS) published online on January 3rd in the journal Drug and Alcohol Dependence. However, the investigators did not measure the quality or function of these cells.
Animal and test tube studies have previously shown that recreational drugs such as cannabis (smoked as marijuana), cocaine, poppers, and amphetamines may adversely affect animal and human T cell responses.
Notably, cocaine given to HIV-infected mice greatly increased HIV levels and reduced CD4 cell counts to one ninth of the levels of the mice in the control group.
However, studies examining the impact of these recreational drugs on CD4 and CD8 T-cells in real life have reported inconsistent and conflicting findings, possibly due to confounding factors such as antiretroviral drug use, injecting drug use, and differences in the level and frequency of recreational drugs used over time.
Consequently, Dr Chun Chao of the University of California at Los Angeles, and her colleagues, sought to assess the association between cannabis, cocaine, poppers, and amphetamine use and CD4 and CD8 counts by examining survey data and medical records from HIV-positive and HIV-negative gay men and other men who have sex with men enrolled in the Multicenter AIDS Cohort Study (MACS).
In particular, they wanted to calculate the rate of CD4 and CD8 change as a function of drug use both at baseline and throughout the study period. In order to explore possible dose-response relationships, they looked specifically at frequency and duration of self-reported recreational drug use.
A total of 3236 HIV-negative men were included in the analysis (which included men enrolled from between April 1984 and April 2003). The average follow-up time for HIV-negative men was ten years.
A further 481 HIV-positive men were included in the analysis. These men were HIV-negative at MACS enrolment and acquired HIV before a cut-off date of December 31st1995, chosen to avoid any confounding effects of highly active antiretroviral therapy (HAART). The average follow-up time for HIV-positive men was five years.
Recreational drug use at baseline was high both for men who remained HIV-negative and those who became HIV-positive during the study.
Of the men who remained HIV-negative, 59% used cannabis, 27% used cocaine, 58% used poppers, and 16% used amphetamines at baseline.
Of the men who seroconverted during the study, 61% used cannabis, 30% used cocaine, 58% used poppers, and 17% used amphetamines at baseline.
Surprisingly, however, the investigators found that fater controlling for smoking (which can raise CD4 cell counts) and other factors known to affect CD4 cell levels, the men who said they used any of the four drugs either at baseline, or any time during the study, had a (non-statistically significant) higher average CD4 cell count throughout the follow-up period, compared to those men who said they did not use any of the drugs.
Consequently, they write, “we did not find any clinically meaningful associations, adverse or otherwise, between use of marijuana, cocaine, poppers, or amphetamines and T cell counts and percentages in either HIV-uninfected or HIV-infected men.”
They add that they “also did not observe any threshold effect by frequency of use or duration of use (at least not with weekly or more frequent use or continuous use in the past year).”
They note that although their study found that the use of poppers was significantly associated with a lower CD4 cell count, “the size of the effect was tiny, even the strongest effect (for weekly or more frequent use) amounting to only a 4% reduction relative to [men] who did not use poppers.”
They also say that although other studies have suggested that cocaine use had an adverse effect on CD4 cell counts “this association was not observed in our study, even in those who used cocaine weekly or more frequently.”
The investigators also looked at the effect of tobacco smoking, and found that “tobacco smoking was associated with approximately 6% (p < 0.01) and 7% increase (p = 0.04) in mean CD4 cell count in HIV-uninfected and HIV-infected men.”
However, in their conclusion, the investigators concede that “although the circulating numbers of CD4 and CD8 T cells do not appear to be significantly affected by use of these substances, these findings do not preclude the possibility that substance use may adversely affect the functional properties of T cells.”
They also fail to point out that recreational drug use can affect sexual risk-taking; that use of poppers was significantly correlated with seroconversion during gay men’s unprotected sexual encounters; that amphetamine use can affect adherence to HAART; and that smoking may undermine the benefits of HAART.