Anal Intercourse Among Young Heterosexuals in Three Sexually Transmitted Disease Clinics in the United States
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ARTICLES Anal Intercourse Among Young Heterosexuals in Three Sexually Transmitted Disease Clinics in the United States Pamina M. Gorbach, MHS, DRPH,* Lisa E. Manhart, PHD,† Kristen L. Hess, MPH,* Bradley P. Stoner, MD, PHD,‡ David H. Martin, MD,§ and King K. Holmes, MD, PHD† prevalence estimates range between 10% and 35% for hetero- Objective: To examine factors associated with heterosexual anal sexual women in the United States and UK1,2,4,5 and as high as intercourse (AI). 40% of US men report AI with a women partner.1 In absolute Methods: Between 2001 and 2004, 1084 heterosexual adults aged numbers, 7 times more US heterosexual women than homo- 18 to 26 attending public sexually transmitted disease clinics in Seattle, sexual men engage in AI.3 In heterosexual samples, reported AI New Orleans, and St Louis were interviewed using computer-assisted ranged from 23% of “nonvirgin” university students6 to 32% of self interview and tested for STIs; Chlamydia trachomatis, Neisseria sexually active women at high risk of HIV in the previous 6 gonorrhoeae, Mycoplasma genitalium, Trichomonas vaginalis, and months7 and is relatively frequent with 7% of sexually active genital herpes (HSV-2). Characteristics associated with AI were iden- respondents reporting AI at least once a month during the tified using logistic regression. previous year in a household survey.8 Results: Overall 400 (37%) reported ever having had AI, 266 Heterosexual AI has been associated with increased HIV (28.9%) reported AI with at least 1 of their last 3 partners, and 19% transmission within serodiscordant couples in the United States reported AI with their last partner. Fewer women than men reported and Brazil9 and with prevalent HIV infection among men and condom use at last AI (26% vs. 45%, P Ͻ0.001). Ever having AI was women attending sexually transmitted disease (STD) clinics in associated with sex on the same day as meeting a partner [AOR 3.9 India.10 This increased risk is likely due to greater efficiency of (95% CI, 2.46–6.21)], receiving money for sex [AOR 2.8 (1.40– transmission and low frequency of condom use during AI. The 5.45)], and Ͼ3 lifetime sex partners [AOR 2.8 (1.56–5.07)] among estimated unadjusted probability of transmitting HIV is 0.08 women, and sex on the same day as meeting a partner [AOR 2.0 per contact for receptive AI,11 as compared with 0.001 per (1.33–3.06]) among men. AI with the last partner was associated with coital act for vaginal intercourse.12 Associations between AI sex toy use [AOR 5.6 (2.63–12.0)] and having concurrent partners and sexually transmitted infections (STIs)9 other than HIV are [AOR 2.2 (1.21–4.11)] among men, and with sex within a week of less consistent. AI has been associated with gonorrhea in the meeting [AOR 2.4 (1.28–4.37)], believing the partner was concurrent general population but not in STD clinic patients.13 Among (AOR 1.9 [1.12–3.22]), and sex toy use [AOR 5.7 (2.31–14.0)] among women, AI has been significantly associated with abnormal women. Prevalent vaginal and urethral sexually transmitted infections anal cytology,14,15 yet little data exist on rectal carriage of other were not associated with AI. STI pathogens, largely because women’s ano-rectal sites are Conclusions: Many young heterosexuals attending sexually transmit- rarely tested. ted disease clinics reported AI, which was associated with other sexual risk There are few data on factors that may influence the behaviors, suggesting a confluence of risks for HIV infection. practice of AI among heterosexuals16 or whether AI places them at higher risk for STIs. Such data could help guide en who have sex with men represent a minority of the US interventions to reduce heterosexual HIV transmission via AI, Mmale population (estimated at 2.3%1–13%2) and most and perhaps clarify whether rectal microbicides for STI pre- (95%) report having engaged in anal intercourse (AI). Less is vention among heterosexuals are needed. Therefore, we as- known about this practice among heterosexuals,3 although sessed individual and partnership characteristics associated with AI among young heterosexual individuals attending 3 geographically distinct US STD clinics. From the *Department of Epidemiology, School of Public Health, University of California Los Angeles, Los Angeles, California; the †Departments of Epidemiology, Medicine, and Global Health, METHODS University of Washington, Seattle, Washington; and the ‡Depart- ments of Anthropology and Medicine, Washington University St. Study Population Louis, St. Louis, Missouri; and the §Louisiana State University Health Sciences Center, New Orleans, Louisiana Between November 2001 and May 2004, 1220 adults Supported by the UW STD CRC (NIH/NIAID AI31448). ages 18 to 26 recruited from waiting rooms in public STD Correspondence: Pamina M. Gorbach, MHS, DrPH, Department of clinics in Seattle, WA, (n ϭ 605), New Orleans, LA (n ϭ 367), Epidemiology, School of Public Health and Division of Infec- and St Louis, MO (n ϭ 248) were interviewed and tested for tious Disease, Geffen School of Medicine, Box 957353, 10880 STIs in the young adults, partnerships, and STD study. Eligi- Wilshire Blvd., Suite 540, Los Angeles, CA 90095-7353. E- bility criteria included presenting with a “new problem” con- mail: [email protected]. Received for publication June 13, 2008, and accepted October 3, 2008. sisting of symptoms of STI, or sexual contact with someone DOI: 10.1097/OLQ.0b013e3181901ccf with STI. IRBs at the University of Washington, WA Univer- Copyright © 2009 American Sexually Transmitted Diseases sity at St. Louis, and Louisiana State University approved all Association study procedures, and approval for data analysis was received All rights reserved. from the University of California, Los Angeles IRB. Sexually Transmitted Diseases ● Volume 36, Number 4, April 2009 193 Gorbach et al. Survey Instrument Of the 920 participants who provided detailed informa- All study subjects participated in a combination of in- tion on their most recent partner, 201 (22%) reported an age terviewer-and computer-assisted self interviews lasting approxi- difference of 5 years or more; more common among women mately 1 hour, which included questions from Wave III of the (33.6%) than men (12.4%), (P Ͻ0.001). Fifty-one percent National Longitudinal Study of Adolescent Heath (Add reported a current partner and among these, an exclusive part- Health)17 as well as more detailed sexual behavior questions. ner was reported by 271 (57.8%), 91 (19.4%) reported a non- The computer-assisted self interview posed questions about the exclusive dating relationship, 48 (10.2%) characterized the participant’s 3 most recent romantic and sexual relationships, partnership as dating infrequently, and 59 (12.6%) said the characteristics of these, sexual experiences, history of and relationship was only for sex. Among women, 59% reported exposure to STI, involvement with the criminal justice system, initiating sex equally, 12% said she initiated sex more; and 29% and substance use. All participants also underwent routine said the male partner initiated sex. A similar proportion of men clinical examination with STI screening. Analyses focus on (57%) reported initiating sex equally; 31% said that he initiated ever having practiced AI and AI with each of the past 3 sex; and 12% said their women partner initiated sex. Overall, partners. Because few participants provided complete informa- 123/587 (21.0%) reported having experienced physical abuse tion on more than 1 partner, our detailed analyses focused on from their most recent partner (i.e., said ‘yes’ to the question AI reported with the most recent partnership. “your partner slapped, hit, or kicked you,”) and 70/587 (11.9%) reported being forced to have sex (i.e., said ‘yes’ to the question Clinical and Laboratory Methods “your partner insisted on or made you have sex when you Clinicians posed questions on sexual history and symp- didn’t want to.”) More men reported physical abuse (27.3%, toms, and performed an external genital (men and women) and 81/297) than women (14.5%, 42/248, P Ͻ0.001). Similar per- speculum (women) exam. Men provided a urine specimen cent of men and women reported being forced to have sex and/or urethral swab, while women provided a urine specimen (13.1% vs. 10.7%, respectively). Physical abuse and forced sex and/or cervical swab, and a self-obtained vaginal swab for STI in the last partnership were significantly associated with re- testing. Mycoplasma genitalium was detected by PCR and ported AI with last partner in men but not women. transcription mediated assay, and Chlamydia trachomatis and Neisseria gonorrhoeae were detected using culture or nucleic Prevalence of AI acid amplification tests, as previously described.18–20 Sus- Overall 400 (37%) reported ever practicing AI; this was pected genital herpes (HSV-2) infection was confirmed by viral significantly different by gender and STD clinic (Fig. 1) al- culture and Trichomonas vaginalis was diagnosed by wet- though not for men across different clinics (Table 1). Of those mount microscopy. “Any STI” was defined as a positive test for who reported AI, 36% (n ϭ 144) reported condom use during any of these pathogens. last AI, but this was reported by fewer women (26%) than men (45%) (P Ͻ0.001). AI with at least one of the last 3 partners Statistical Methods was reported by 266 (28.9%); AI with the last partner was In univariate analyses, categorical variables were as- reported by 15.7% of men and 22.6% of women (P ϭ 0.008). sessed using Fisher Exact or Pearson chi squared test, whereas Overall, the proportion ever engaging in AI increased steadily continuous variables were assessed using the Wilcoxon rank with age, going from 23% among 18 year old to 46% of 25 year sum test.