Although methamphetamine (meth) use is not a new phenomenon, meth may be one of the least understood major illicit substances used in the United States.1 One potential explanation is that in comparison with other major illicit substances such as marijuana, cocaine, or opiates, meth is a relatively new drug.1 Methamphetamine use is a significant problem in the United States because of its association with negative health outcomes including increased risk for acquiring sexually transmitted infections (STIs) in both men and women.2 According to the 2011 National Survey on Drug Use and Health (NSDUH), the overall prevalence of meth use in the past year was estimated to be 0.4%,3 with the highest prevalence among young adults aged 18 to 25 years (0.7%).3 An NSDUH report examining meth use by race/ethnicity from 2002 to 2004 found that past year meth use was higher among Whites (0.7%) as compared with Hispanics or Latinos (0.5%), Asians (0.2%), and Blacks or African Americans (0.1%).4 The report also indicated that meth use varies by region, with the highest prevalence in the Western and Midwestern United States (ranges from 0.98% to 2.21%).4
The association between meth use and sexual risk taking has been well documented in men and predominantly among men who have sex with men (MSM).5 Studies have shown that meth use in men has been associated with high-risk sexual behaviors such as having a higher number of sexual partners, infrequent condom use, trading drugs or money for sex, having sex with a partner who is an injection drug user (IDU), as well as report of a recent STI.2,6 However, fewer studies have been conducted to examine the relation between meth use and STI risk among women, although there are data suggesting that the proportion of meth use by sex is more similar than other illicit substances, as indicated by a 2007 literature review.7
Available literature suggests higher rates of bacterial STIs reported in female as compared with male drug users, who could be more susceptible to STIs owing to increased likelihood of asymptomatic infection and the practice of exchanging sex for money or drugs.8 One study of IDUs found that meth-injecting women were more likely to have unprotected vaginal sex and multiple sex partners as compared with women who injected other substances.9 A recent review of sexual behaviors among heterosexual drug users indicated that women meth users were at increased risk for engaging in unsafe sexual behaviors10; other studies document that women experience a heightened sex drive and increased number of sexual acts.11,12 Qualitative data also suggest that meth use increases sexual desire and pleasure and reduces inhibition, which can alter sexual behaviors in women.13
Despite existing evidence, there is a need for further research on risk behavior among women who use meth because of their potentially high risk for STIs/HIV.10 The available sexual risk behavior studies conducted on women meth users rarely use laboratory-confirmed STI test results, and many do not distinguish meth use from other types of illicit substance use.14,15 In addition, meth-using women attending sexually transmitted disease (STD) clinics are relatively understudied. This is of particular importance because STD clinics could potentially serve as outlets for delivering STI prevention and treatment interventions for drug users.8 Thus, our objective was to identify demographic and behavioral factors associated with meth use, including associations with STIs, among a diverse group of women attending public STD clinics in Los Angeles County. We hypothesized that women reporting meth use would have higher reported rates of risky sexual behaviors and would be at a higher risk for chlamydia and gonorrhea (CT/GC) as compared with non-users.
Study Population and Design
We conducted a cross-sectional study of female clients attending 12 public STD clinics in Los Angeles County, California. All women who came for a new visit, which was defined as an initial visit for a new complaint, between January 2009 and December 2010 were included in the analysis. A total of 22,885 visits to the STD clinics were completed by 16,300 unique women during the study period.
Demographic and sexual risk behavior data were collected as part of the clinic intake process in a face-to-face interview conducted by specialized clinical staff. Specifically, female clients were asked about the sex of sexual partners in the past 12 months and whether any of these partners were injection drug users, anonymous partners, men who also had sex with men, HIV positive or had been recently incarcerated. In addition, women reported whether in the past 12 months they had anal, oral, or vaginal intercourse; exchanged drugs/money for sex; were incarcerated; or used substances such as meth, cocaine or “crack,” marijuana, heroin, and ecstasy. Frequency of condom use (always, sometimes, or never) was reported for the past 90 days.
Laboratory results on CT/GC testing were collected from the laboratory database. Gen-Probe Aptima Combo 2 (San Diego, CA) nucleic acid amplification tests were used for all CT/GC tests. All women seen for new visits at the clinics were routinely tested for urogenital CT/GC. In addition, some women were also tested for rectal chlamydia/gonorrhea and/or pharyngeal gonorrhea. Clinic guidelines recommended targeted rectal CT/GC testing among women reporting recent anal intercourse (past 90 days) or rectal symptoms. Pharyngeal gonorrhea testing was recommended for women reporting any oral sex who also report symptoms, contact to a partner with gonorrhea, or other high-risk exposure. Data on routine HIV and syphilis screening were excluded. Sexually transmitted infection positivity was defined as any positive chlamydia or gonorrhea test result including urogenital, rectal, and pharyngeal infections.
χ2 Tests were used to compare the prevalence of reported meth use among women with different demographics, sexual risk behaviors, condom use, substance use, and STI test results. Differences in meth use by age were analyzed using a Wilcoxon rank sum test. We used a multivariable logistic regression model to identify predictors of meth use after controlling for the potentially confounding effects of age, race/ethnicity, condom use, other illicit substance use, partner type, and the occurrence of a new recent sexual partner. We also checked for an interaction between anonymous partner and exchanging sex, which was not found to be significant. Because it was possible for a client to have multiple clinic visits during the study period, we used a hierarchical regression model with type 3 generalized estimating equations to account for within-participant correlations and to avoid analyzing paired data. We explored potential correlates of meth use based on the information that was available via preexisting standard risk behavior intake forms in use at the STD clinics. To be included in the final model, all covariates were required to be specified a priori as risk factors for meth use based on previously existing literature.2,10 Owing to missing data for several variables, a total of 13,273 observations were used in the final model. All statistical analyses were performed with the SAS software version 9.2.
Demographic and Behavioral Characteristics
From 2009 to 2010, there were a total of 22,885 clinic visits completed by women and included in the analysis. These include 16,300 unique women at their most recent visit. Their mean (SD) age was 31.5 (12.5) years, with 57% of women being younger than 30 years (Table 1). Most women were African American (47%) or Hispanic (32%), whereas 13% identified as White. Most women across all visits (94%) reported only male sex partners, and almost one third had a new sex partner in the past 90 days. A total of 2722 women, or 13%, were tested positive for chlamydia and/or gonorrhea at one of their clinic visits.
Prevalence of Meth Use by Sample Characteristics
Methamphetamine use in the past year was reported by 1.4% (n = 277) of women across all study visits (Table 2). The prevalence of meth use was highest in Whites (4.4%), followed by Hispanics (2.4%), and lowest among African Americans (0.2%). Younger women (mean age, 28.5 years) and those who reported both male and female partners were more likely to use meth compared with older women (mean age, 30.5 years) or women reporting only male or only female partners. In addition, most women who reported meth use also reported using other substances (Fig. 1). Of those women who reported meth use in addition to at least one other substance, more than 80% reported also using marijuana; 32%, cocaine/crack; 21%, ecstasy; and 16%, heroin in the past 12 months. In contrast, non-meth users who reported using at least one other substance had a much lower prevalence of marijuana, cocaine/crack, ecstasy, and heroin use as well as polysubstance use (Fig. 2).
The prevalence of meth use also varied by sexual risk behaviors (Table 2). Women who reported a new sexual partner in the preceding 90 days were more likely to report meth use than those who did not (2.2% vs. 1.1%; P < 0.01). Other reported sex partner characteristics related to meth use included having a recently incarcerated partner and having a partner who reported sex with both women and men, with the highest prevalence noted among women who reported a sex partner who was an IDU (33.1% vs. 1.1%; P < 0.01). Meth use was also higher among women who reported transactional sex or being incarcerated and was inversely associated with condom use. Specifically, women who reported consistent condom use for vaginal sex had a substantially lower prevalence of reported meth use as compared with those who reported using condoms only “sometimes” or “never” (0.7% vs. 1.3% vs. 1.8%, respectively; P < 0.01). Finally, women who tested positive for chlamydia or gonorrhea had a higher prevalence of meth use in comparison with those who tested negative (1.9% vs. 1.3%; P = 0.04).
Factors Associated With Meth Use
In a multivariable model controlling for age, race/ethnicity, condom use, having a new sex partner, and other illicit substance use (including marijuana, cocaine/crack, ecstasy, heroin, or “other”), we found that certain partner characteristics as well as STI status were associated with meth use. Women who reported sex with an IDU were nearly 10 times more likely to report meth use as compared with those without an IDU sex partner (adjusted odds ratio [AOR], 9.90; 95% confidence interval [CI], 5.86–16.75; Table 3). Other characteristics associated with meth use included sex with a recently incarcerated partner (AOR, 3.24; 95% CI, 2.16–4.86), anonymous partner (AOR, 2.49; 95% CI, 1.54–4.04), and trading sex for drugs or money (AOR, 3.26; 95% CI, 1.69–6.32). Furthermore, women who tested positive for chlamydia or gonorrhea had a 48% increased odds of meth use as compared with those who were not test positive.
Our study is one of the few to associate sexual risk behaviors among female meth users with verified STI diagnoses in a clinic-based sample. We found the prevalence of meth use in the past 12 months to be 1.4%, which is higher than the 0.5% prevalence estimated from a 2002–2004 national survey of women older than 12 years.4 Meth use by racial/ethnic group was similar to national patterns, with a higher prevalence occurring among Whites as compared with Hispanics and African Americans. Our findings suggest that more women who attend STD clinics use meth than those in the general population; however, it is also possible that our sample is a reflection of the higher prevalence of meth use that occurs in the Western region of the United States.16 Past year prevalence of meth use from 2002 to 2005 in California was estimated to be 1.13% according to an NSDUH report,17 which is more similar to our finding of 1.4%. The prevalence of past-year meth use in our study was lower than that reported among other high-risk subgroups in California, such as HIV-positive women receiving treatment (11%; n = 122) in 200618 and the past 30-day prevalence of meth use among homeless women (9%; n = 100) from 1996 to 2003.19 Although fewer women attending STD clinics reported meth use than in these very high-risk subgroups, women attending STD clinics represent an important group for assessing substance use such as meth because of their added increased risk for STIs/HIV.
We confirmed previous findings that women who reported meth use were also likely to report high-risk sexual behaviors such as transactional sex, history of an STI, sex with an IDU partner, and decreased condom use.2,6,10,15 We detected a much stronger association (ie, larger odds ratio) between having an IDU partner and meth use than that reported in a similar study of non–injection drug–using women.2 Because having an IDU partner was independently and strongly associated with meth use, this suggests that women presenting at STD clinics who report meth use are not only at increased risk for CT/GC but are also at greater risk for HIV and hepatitis B and C.20,21 This is in agreement with previous studies indicating that women may be more likely than men to have overlapping drug use and sexual partner networks22,23 and suggests that female meth users are at increased risk for HIV/STIs and other adverse health outcomes.
Women presenting at STD clinics who report meth use may need tailored interventions to address the level of risk associated with their sexual partnerships. For example, it may be important to assess whether sex with an IDU partner is a transactional event or a main partnership and the level of risk involved (ie, condom use), to tailor counseling messages accordingly. Understanding the context of sexual partnerships can lead to better targeted prevention messages. In addition, interventions could directly address prevention or treatment of meth use among women to reduce meth-related risky behaviors, such as by enrolling in drug treatment or needle-exchange programs.8,24 Sex-specific and partner-centered harm reduction and treatment interventions would be especially beneficial given the importance of meth-using sexual partnerships in maintaining risk behaviors.25 Integration of services is important in preventing STIs and because meth use was found to be relatively common in this population attending STD clinics, these women could benefit from a coordinated approach at STD clinic facilities.8
Few studies have examined the prevalence of polysubstance use in relation to meth use among female substance users attending STD clinics. Polysubstance use is an important factor to consider because meth users may face additional health risks due to polysubstance use.26 Results from our multivariable model indicated that the use of other illicit drugs is associated with meth use, and this was true even when marijuana was not included in the definition of “other illicit substance use” (data not shown). Although many women reported substance use in addition to meth, meth use remained associated with STIs and high-risk sexual behaviors even when the use of other illicit substances besides meth was taken into consideration. This suggests that among women, similar to MSM,2 the relationship between meth use and STI risk is independent of the use of other illicit drugs.
There are several limitations to our study. First, assessment of meth use and sexual risk behaviors was based on self-report during a face-to-face interview. Sensitive or illicit information that is self-reported during an interview is susceptible to bias because respondents may be reluctant to disclose this type of information even when collected in the context of health care.27 It is likely that use of all substances including meth was underreported, as was other sexual behaviors that may be difficult to report to an interviewer. Our assessment of positive CT/GC results using confirmed laboratory tests instead of self-reported measures is a strength because it increases the accuracy of our outcome measures and limits the misclassification that would have been associated with self-report of STI diagnosis. Second, participants in this study were women who voluntarily attended public STD clinics, and this population may not be generalizable to other populations of women. Because our sample is limited to Los Angeles County, we may have detected a higher prevalence of meth use because of regional variations in the pattern of meth use. Third, the risk of HIV and syphilis was not addressed in this study owing to the lack of a sufficient number of HIV cases and the difficulty involved in distinguishing true syphilis cases. Fourth, STI event-level and partner linkage data were unavailable, which makes it unclear as to which partner conferred the highest STI risk. Finally, because this is a cross-sectional study, we cannot directly infer that meth use causes high-risk sexual behavior because of our uncertainty regarding the time ordering of events. However, the strong association observed between meth use in the past 12 months and high-risk sexual partner types indicates that female meth users may be part of a high-risk sexual network, which increases STI risk.
The prevalence of meth use and its relation to sexual risk behavior is an important issue that has not been closely studied among women with a current STI diagnosis. This study contributes to a better understanding of the pattern of meth use among women at risk for or infected with HIV/STIs by examining women attending public STD clinics. We found a high prevalence of meth use among women attending public STD clinics in Los Angeles County in comparison with the national population. Furthermore, our findings indicate that meth use is an important marker for high-risk sexual behaviors and polysubstance use in women, although the reasons for its use as well as its behavioral correlates may differ from that in men.11,15,28,29 Our results warrant the need for improved resources and interventions for meth-using women because of their unique STI risk as compared with non-users. Our study provides evidence for the association between meth use and STI risk among women that is consistent with previous research and further elaborates upon the partner type and substance use patterns of these women. In particular, further research is needed to better describe the risk factors among meth-using women and infections associated with chronic diseases such as HIV and hepatitis C.
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