Methamphetamine use before or during a sexual encounter, which has a well-established association with risky behavior among men who have sex with men, may also be a predictor of risky behavior in heterosexual encounters. In a study conducted among injection-drug users in North Carolina, three of six risky behaviors examined were more likely to occur in heterosexual encounters involving use of the drug than in others; although use by one partner was not associated with elevated odds of any of these activities, use by both was associated with sharp increases in the likelihood of five of the six.¹

The study was based on data collected between 2003 and 2006 from 703 men and women aged 18 and older who said that they had injected drugs in the previous 30 days and were not currently receiving treatment for substance abuse. With information participants provided about a total of 1,213 recent heterosexual encounters, the researchers used multivariate generalized estimating equations to assess relationships between methamphetamine use and six behaviors: unprotected vaginal intercourse, anal intercourse, unprotected anal intercourse, vaginal and anal intercourse during the same encounter, sex with a new partner and unprotected intercourse with a new partner. The analyses controlled for each partner’s age, the male’s race, cocaine use during the encounter and, for all behaviors except the two involving new partners, partner type (main or casual).

Participants were 41 years old, on average; the majority were male (73%), black (62%) and unemployed (71%). Half had graduated from high school, two in 10 were married or living with a partner, and one-third were homeless. Eleven percent said that they had used methamphetamine in the past 30 days, and 62–72% reported having used each of several other drugs (crack, alcohol, heroin, powder cocaine and marijuana). Some 27% had had multiple sex partners in the past 30 days, 39% had had unprotected vaginal intercourse and 9% had had anal sex.

At the bivariate level, recent methamphetamine users were more likely than nonusers to be white, homeless and unemployed, and were less likely to be high school graduates. During the past 30 days, they were more likely to have used other drugs, to have had more than one sexual partner or a partner who injected drugs, and to have engaged in anal intercourse.

Nearly all sexual encounters (89%) involved vaginal sex, and 9% involved anal intercourse; in slightly more than half of each of these types of encounter, the couple did not use condoms. Eighteen percent of encounters involved no substance use, 28% involved use by one partner and 54% use by both. Alcohol was the most commonly used substance (reported in 56% of sexual encounters), and methamphetamine the least (7%).

In the multivariate analysis, any methamphetamine use before or during a sexual encounter was associated with a roughly doubling of the odds of three risky behaviors: anal intercourse (odds ratio, 2.4), both vaginal and anal intercourse (2.4) and sex with a new partner (2.0). However, results were strikingly different in separate analyses examining encounters involving one partner’s and both partners’ use of methamphetamine. Use by only one partner was not associated with any of the risky behaviors studied, but use by both partners was associated with an increased likelihood of four of the six: anal intercourse (4.7), both vaginal and anal intercourse (3.7), sex with a new partner (5.0) and unprotected sex with a new partner (5.0).

The researchers note that event-level analyses of substance use and heterosexual activity have been rare, and that more such studies will be key to creating effective STD prevention interventions that "address the possibility of multiple and varied sex acts—thus, multiple and varied infection risks—during any single encounter." Meanwhile, they conclude, health professionals who provide care to methamphetamine users should work toward "developing strategies and messages…for reducing risks associated with sex while using methamphetamine."

Reference

1. Zule WA et al., Methamphetamine use and risky sexual behaviors during heterosexual encounters, Sexually Transmitted Diseases, 2007, 34(9):689–694.