Methamphetamine use significantly boosted a sexual risk score that predicts HIV acquisition in a study of 8,905 U.S. men who have sex with men (MSM). Researchers who conducted this six-year retrospective analysis propose that MSM who use meth "may represent ideal candidates" for pre-exposure prophylaxis (PrEP).
Use of illicit drugs including methamphetamine is more prevalent among MSM than in the general population, particularly before and during sex. Research links methamphetamine to HIV-risk behavior in MSM. But whether this central nervous system stimulant causes risky sex cannot be determined with certainty because a randomized trial would be unethical. Researchers at the University of California, San Diego (UCSD), tried to fashion a surrogate for randomization in this study by comparing sexual behavior before and after MSM started using methamphetamine.
The study involved MSM at least 13 years old who had at least one HIV test as part of the San Diego Early Test (SDET) HIV screening program between April 2008 and July 2014. For each testing encounter, researchers calculated SDET scores, which predict risk of HIV acquisition. On a scale of 0 to 10, scores above 5 are associated with a six-fold higher risk of acquiring HIV. A four-question survey completed at each test visit established whether men had used meth in the previous 12 months (defined as recent-meth use) or never used meth (never-meth). Researchers assigned men with two or more tests to one of four groups: (1) started using meth, (2) stopped using meth, (3) continued meth or (4) never-meth. The investigators determined changes in sexual risk behavior and SDET scores from the first test to the most recent test.
The analysis focused on 8905 MSM who had 17,272 HIV tests during the study period. Among those 8905 men, 1788 (20%) had a repeat test more than 12 months after the first test. While 754 men (8.5% of 8905) reported recent meth use, 5922 (66.5%) reported never using meth. The recent-meth and never-meth groups had the same median age (32 years), and similar proportions were white (53.6% and 53.5%), Hispanic (28.2% and 27.3%) or black (5.0% and 4.9%).
Median SDET sexual risk score was significantly higher among recent meth users than among never-users (5 versus 0, P < .001). While 54% of recent-meth users had an SDET score of 5 or greater, only 6% in the never-meth group had a score that high. Proportions of the recent-meth group and never-meth group that had condomless receptive anal intercourse with an HIV-positive partner were 29.4% and 5.7%, while respective proportions with 10 or more male partners were 59.7% and 31.4% (P < .001 for both).
Among 1788 MSM who had more than one HIV test at least 12 months apart, 185 (10.3%) reported recent meth use at the first and/or most recent test. Among these 185 meth users, 82 (44.3%) started using meth between their HIV tests, 48 (25.9%) continued using meth and 55 (29.7%) stopped using meth. Among 82 men who started using meth between their HIV tests, median SDET score rose significantly between testing visits from 3 to 5 (P < .001). Among men who stopped using meth or continued using meth between visits, median SDET score did not change significantly.
The researchers then broadened the analysis to include 2456 MSM with a repeat test at any time (rather than after at least 12 months). In that group, at their first and/or most recent test 224 men (9.1%) reported using meth. Among 89 of those 224 men (39.7%) who started using meth between HIV tests, median SDET score rose significantly from 3 to 5 (P < .001).
Multivariable logistic regression analysis identified recent meth use as the strongest predictor of an SDET score above 5 (odds ratio [OR] 3.191, 95% confidence interval [CI] 2.528 to 4.028), followed by recent gamma hydroxybutyrate (GHB, G, liquid G, liquid X) (OR 2.178, 95% CI 1.657 to 2.862) and recent nitrites (poppers) (OR 1.911, 95% CI 1.580 to 2.311) (P < .001 for all).
The authors note that methamphetamine use can heighten libido, boost sexual pleasure, prolong sexual performance and make receptive anal intercourse less painful. These effects could combine to favor transmission of HIV and other sexually transmitted pathogens. Methamphetamine also dries mucosa, the researchers add, and resulting sex-induced abrasions could further boost HIV-acquisition risk.
Because sexual risk behavior rose among MSM who started meth between HIV test visits and did not drop significantly in men who stopped using meth, the authors suggest that "meth use may be associated with a relatively rapid increase in risk behavior that may not be fully reversible." Therefore, they propose that MSM may need "very early prevention interventions" before they start using meth.