Gay men who use methamphetamine have greater risk of HIV seroconversion

Large cohort study finds link between methamphetamine, unprotected sex, and HIV seroconversion

Investigators from the MACS cohort, an ongoing longitudinal study involving thousands of gay men recruited in waves since the mid-1980s, therefore designed a study to examine the association between methamphetamine, and other drug use, and sexual risk behaviour amongst men who were HIV-negative when they entered the cohort. In particular, they wished to see if the use of methamphetamine or any other drug increased the risk of unprotected sex and HIV seroconversion.

Every six months, men provided details of their drug taking and sexual behaviours and were tested for HIV. A total of 4,003 gay men, recruited to the cohort from 1985 to 2004, were included.

After adjusting for potentially confounding factors, the investigators found that men who reported use of methamphetamine had a relative risk of HIV seroconversion of 1.46 compared to men who did not use the drug. This risk increased to 2.10 if methamphetamine was used with poppers.

The investigators also established that the risk associated with methamphetamine use and HIV seroconversion increased, unsurprisingly, with the number of men a man had unprotected receptive sex with. A man reporting methamphetamine use and receptive unprotected sex with one partner had a relative risk of HIV seroconversion of 1.87. This risk increased to 9.32 for men who used methamphetamine and had receptive unprotected sex with five or more men.

Men who used both methamphetamine and poppers had an even greater risk of HIV seroconversion. Again, this risk increased with the number of partners a man had unprotected receptive anal sex with, the risk being 2.71 for men reporting one partner, but 13.57 for men using methamphetamine and poppers during unprotected receptive sex with five or more partners.

The investigators are unable to say from their research why the use of methamphetamine and poppers together contributed to an increased risk of HIV seroconversion, but speculate that “it is likely to be a multifactorial process involving behavioural disinhibition, anal trauma, and selection bias for higher risk sexual partners."

Use of methamphetamine (often called crystal meth) by gay men is associated with unprotected sex and HIV seroconversion, according to two recently published American studies.

Investigators from the Multicenter AIDS Cohort Study (MACS) found that gay men who used methamphetamine and poppers during sex, and who had unprotected sex with five or more partners had an extremely high risk of contracting HIV. Their findings are published in the May 1^st edition of the Journal of Acquired Immune Deficiency Syndromes.

A smaller study involving gay men in California, published in the June edition of Sexually Transmitted Diseases, also found a clear association between the use of methamphetamine and an increased risk of infection with HIV. The Californian investigators also found that methamphetamine use often occurred alongside the use of other illicit substances, reflecting the findings of UK research that the small number of British gay men who used methamphetamine were poly-drug users.

Use of methamphetamine has been popular with gay men in the US for many years. It has a powerful stimulating effect on the central nervous system and many individuals report that it enhances sexual enjoyment. Previous studies have suggested that gay men who use methamphetamine are more likely to have unprotected anal sex.

Few studies, however, have examined the link between use of methamphetamine and the risk of acquiring HIV infection. A better understanding of the relationship between drug use and HIV infection risk could, investigators believe, lead to the development of improved HIV prevention strategies.

Use of poppers can also enhance sexual pleasure and some studies have also suggested that their use can be associated with an increased risk of acquiring HIV infection. There is also substantial evidence suggesting that methamphetamine and poppers are often used together.

Californian study – methamphetamine use often occurring within the context of other drug use

Investigators in Los Angeles wished to determine the relationship between the use of illegal drugs and unprotected anal sex amongst gay men before and after seroconversion with HIV. They therefore designed a study involving 207 gay men with an estimated recent date of HIV seroconversion. These men were asked to provide details of their last three sexual partners and to say if drugs were used during sex with these men.

Data were collected a median of 13 weeks after the estimated date of HIV seroconversion. The men had a median age was 35 years, 70% were white, 46% were college graduates, and the median number of sexual partners in the previous three months was nine. Overall, 12% of all sexual partners were known to be HIV-positive, 42% were known to be HIV-negative, and 46% were of unknown status.

Before HIV seroconversion, unprotected sex was strongly associated with methamphetamine use (odds ratio, 7.12, p = 0.01). An association was also found between unprotected sex and the use of methamphetamine and other illicit substances (odds ratio, 4.06, p

“Methamphetamine use was associated with a greater odds of unprotected anal intercourse before HIV diagnosis but was not associated with unprotected anal intercourse after diagnosis”, write the investigators, adding, “in contrast, use of substances other than methamphetamine were not associated with unprotected anal intercourse before HIV diagnosis but were associated with a greater likelihood of unprotected anal intercourse after diagnosis.”

The investigators also recorded a “modest” reduction in the number of partners with whom men reported unprotected sex with after their HIV diagnosis. They suggest that this represents “a deliberate reduction in transmission behaviours.”

“There was a considerable overlap in use of many different substances (i.e. poly-drug use) with a single partner among our participants”, note the investigators. The 2005 UK Gay Men’s Sex Survey found similar evidence of poly-drug use amongst the few men it identified as using methamphetamine.

The investigators conclude “new interventions designed to reduce HIV transmission among men who have sex with men through cessation of substance use should consider different types of substance use, including poly-drug use.”