Sexually Transmitted Diseases:
The Effect of Venue Sampling on Estimates of HIV Prevalence and Sexual Risk Behaviors in Men Who Have Sex With Men
Xia, Qiang MD, MPH*†; Tholandi, Maya MPH*; Osmond, Dennis H. PhD‡; Pollack, Lance M. PhD‡; Zhou, Wei MS§; Ruiz, Juan D. MD, MPH, DrPH*; Catania, Joseph A. PhD‡
From the *California Department of Health Services, Office of AIDS, Sacramento, California; the †Neuropsychiatric Institute Center for Community Health, University of California, Los Angeles, Los Angeles, California; and the ‡Center for AIDS Prevention Studies, University of California, San Francisco, San Francisco, California; and the §Department of Statistics, University of California, Davis, Davis, California
This study would not have been possible without the extensive cooperation of the respondents who were willing to participant the project. The authors also thank Dr. E. Richard Brown at University of California, Los Angeles, Center for Health Policy Research, for his technical assistance, and J. Michael Brick, Ismael Flores Cervantes, W. Sherman Edwards, Alan Martinson, and Vasudha Narayanan at WESTAT Corporation for their data collection and statistical assistance.
Support for this study was provided by the California Department of Health Services, Office of AIDS under a cooperative agreement (01-16085) to Dr. Joseph A. Catania at the Center for AIDS Prevention Studies, University of California, San Francisco. Support for Dr. Catania was also provided by UARP ID04-SF-008 and NIH MH54320.
Correspondence: Joseph A. Catania, PhD, Center for AIDS Prevention Studies, University of California, San Francisco, 74 New Montgomery, Suite 760, San Francisco, CA 94105. E-mail: email@example.com
Received for publication July 7, 2005, and accepted December 14, 2005.
Objective: The objective of this study was to investigate differences in HIV prevalence and sexual risk behaviors among men who have sex with men (MSM) according to their gay venue visit patterns.
Methods: In a cross-sectional survey, a population-based sample of men aged 18 to 64 years who self-identified as gay or bisexual were interviewed by telephone regarding their sexual behaviors, HIV serostatus, and gay venue visit patterns.
Results: A total of 398 men were recruited for the study. The results showed that frequent gay venue visitors were more likely to engage in high-risk sexual behaviors. Among gay venue attendees who visited different types of gay venues, men who visited sex clubs/bathhouses reported the highest rates of 5 or more male sexual partners and unprotected anal intercourse (UAI) with secondary partners (62.6% and 34.6%, respectively), gay bar/club attendees and cruisers reported higher rates of having sex with women (8.5% and 14.8%, respectively), and circuit party attendees reported the highest HIV prevalence (40.4%) and serodiscordant UAI (30.2%).
Conclusions: MSM who visited different types of gay venues and with varied visit frequency showed marked differences in sexual risk behaviors, and the differences suggest the importance of weighting procedure to obtain unbiased estimates in venue-based studies.
SOCIAL SCIENTISTS HAVE INVESTIGATED THE environments outside the home where men who have sex with men (MSM) meet other men for casual, usually anonymous, sex. 1–3 The variety of settings is large, but in general they can be categorized into 4 groups: 1) commercial not-for-sex environments (e.g., gay bars/clubs), which provide services other than opportunities for sex but can be used as sex venues4–6; 2) commercial sex environments (e.g., sex clubs and bathhouses), which primarily provide opportunities for sexual encounters between men7–9; 3) public sex environments or cruising areas (e.g., parks, alleys, and beaches), which are public spaces where MSM actively seek sex10,11; and 4) circuit parties, which typically involve weekend-long series of social events, during which risky sexual behaviors and drug use may be particularly frequent.12–15
Recent studies have documented increased sexual risk-taking behaviors, sexually transmitted infections, and human immunodeficiency virus (HIV) infection incidence among MSM in the United States and the world.16–22 Some studies have been based on convenience samples from a few venues or venues of one particular type (e.g., gay bars/clubs, bathhouses, or cruising areas); therefore, the results may be biased, because participants from one venue may not be representative of all venues of that type or of other types of venues. Studies have demonstrated differences in sexual risk behaviors among MSM who visit gay bathhouses, public cruising areas, and both,23 and differences in sexual orientation between bathhouse and park users.24 However, no study has used a population-based sample to investigate differences in characteristics, HIV prevalence, and sexual risk behaviors among MSM from all 4 types of gay venues.
To take into account the difference in sexual risk behaviors among men who visit different types of gay venues, HIV behavioral surveillance and other studies have historically relied on venue–day–time sampling to recruit MSM.25–30 In venue–day–time sampling, a universe of venues is created during formative research by identifying all public venues within a defined area frequented by MSM. Ideally, every MSM who attends these venues has a known, nonzero probability of being selected. However, those making frequent visits have a greater chance of being enrolled, and the findings may be substantially biased toward the frequent visitors, who may practice riskier behaviors. One study demonstrated no association between frequency of gay venue attendance and HIV prevalence,29 but no study has shown the relationship between frequency of gay venue attendance and sexual risk behaviors.
Using data from a probability telephone sample, this report investigates the differences in HIV prevalence and sexual risk behaviors among MSM according to their gay venue visit patterns: type of venues and frequency of attendance.
Participants and Sampling Design
Data were from the California Health Interview Survey (CHIS) MSM Follow-up Study, a telephone survey conducted from May 5 through June 23, 2002, and based on a probability sample of MSM living in California. The methodology of this survey has been previously described in detail.31 Briefly, the target sample was defined by men aged 18 to 64 who self-reported as gay or bisexual in CHIS 2001 but, regardless of their orientation, were screened for same-gender sexual behavior in the past 10 years. Of a total of 875 men who self-identified as gay (n = 593) or bisexual (n = 282) in CHIS 2001, 741 (84.7%) agreed to participate in the CHIS MSM Follow-up Study. No statistical difference was found between the men who agreed to participate and those who did not in terms of age, race, and metropolitan statistical area (MSA) status (Los Angeles MSA, San Francisco MSA, MSA1 [other large MSA], MSA2 [smaller MSA], and not MSA).
Among 741 respondents who gave consent for follow up, 193 (26.0%) were not reachable and 114 (15.4%) men were excluded because of no sex with a male in the past 10 years, leaving a total of 434 (58.6%) respondents eligible for the study. Thus, the obtained sample was of sexually active (in the past 10 years) MSM aged 19 to 65. Of the 434 eligible respondents, 398 (91.7%) completed the interview in English or Spanish for 30 to 45 minutes.
Respondents reported basic demographic data, including age, race/ethnicity background, education, annual income, city/rural area of current residence, and length of residency.
Respondents reported the results of their last HIV antibody tests if they had tests done before. Men who self-reported HIV negative or of unknown HIV status and agreed to have an HIV test were provided a home urine specimen collection kit (Calypte Biomedical Corp., Berkeley, CA). The presence of HIV antibodies was demonstrated by enzyme immunoassay (Calypte Biomedical Corp.), and positive results were confirmed by Western blot (Calypte Biomedical Corp.). A card provided as part of the test kit contained the respondent's study identification number and instructed him to call for test results 3 weeks after sending in his urine sample. The card also provided a toll-free telephone number for this purpose and the days of the week and time of day when they could call. Respondents identified themselves on the telephone by their identification number only. Test results and counseling were provided over the telephone by a certified HIV counselor. Self-reported HIV-positive men were not tested because previous research had shown 100% confirmation of self-report by oral HIV test kit in a telephone sample of MSM.32 HIV prevalence data were computed based on the combined data from self-report and urine test results.
Frequency of Gay Venue Visit.
Respondents were asked a series of questions related to how frequently they visited specific gay venues in the past 12 months: “How often have you gone to a gay bar or club that primarily serves a gay crowd?” “How often have you gone to a bathhouse or sex club with primarily a gay clientele?” “How often have you gone to a t-room, adult bookstore, X-rated theater, park, beach, or other cruising area?” “How often have you gone to a gay ‘circuit party' in the United States or some other country?” The number of visits to each type of gay venue in the past 12 months was summed up to create a new variable of the frequency of “any gay venue” visit.
Sexual Risk Behaviors.
Respondents were first asked whether they had had sex with men, women, or both in the past 12 months, followed by a series of questions about their sexual behaviors with male partners, including number of male sexual partners and number of partners with whom they had engaged in various sexual behaviors (insertive and receptive anal intercourse with and without a condom). They were also asked about their sexual behaviors on a partner-by-partner basis (frequency of insertive and receptive anal intercourse with and without a condom and their partner's HIV status) for their current primary partner and up to 3 other partners, or for up to 4 partners if they did not have a primary partner. The information was combined to determine whether a respondent had engaged in unprotected anal intercourse (UAI) with a secondary partner in the past 12 months. Partner-by-partner information, including knowledge of the partner's HIV status, was used to determine whether UAI occurred with a serodiscordant partner.
Cases were weighted to account for the probability of selection, nonresponse, and undercoverage. The replicate jackknife method was used to estimate standard errors by using 80 replicate weights, which were created with paired jackknife method. All data in this report were weighted unless indicated otherwise.
We described the frequency of visits to each particular type of gay venue among MSM living in California, and performed chi-squared tests to examine the differences between men who did and who did not visit any type of gay venue in the past 12 months.
Then, we presented estimates of HIV prevalence and sexual risk behaviors for MSM who visited each type of gay venue, MSM who visited at least once any type of gay venue in the past 12 months (the venue sample), and all MSM (the population sample), including the venue sample and men who did not visit any gay venue in the past 12 months. Because many men visited more than one type of gay venue and they could be included in more than one group (e.g., one man can be in both gay bar/club and sex club/bathhouse group), we made our comparisons based on the results of point estimates when we compared men who visited different types of gay venues.
Finally, logistic regression models were used to assess the relationship between the frequency of gay venue visits and HIV prevalence and its associated sexual risk behaviors using crude odds ratio (OR) and adjusted odds ratio (AOR) controlling for age, race/ethnicity, and residence. All analyses were conducted with SUDAAN,33 which accounts for the complex sample design.
Table 1 summarizes the gay venue attendance among MSM living in California. Overall, 83.5% (95% confidence interval [CI]: 71.0–96.5%) of MSM in our sample reported visiting a gay venue at least once in the past 12 months. Gay bars/clubs are the main venues that MSM frequented with 29.1% (95% CI: 23.7–35.2%) visiting more than once a month and 47.3% (95% CI: 40.4–54.3%) visiting less than or equal to once a month. Only 17.5% (95% CI: 12.3–24.5%) of MSM visited sex clubs/bathhouses. Approximately one in 9 (11.4%) MSM attended at least one circuit party in the past 12 months.
In Table 2, we first compared the difference between MSM who did and who did not visit any type of gay venue in the past 12 months. Younger MSM (P < 0.01) and MSM of color (P < 0.01) were more likely to attend gay venues. Less educated MSM reported attending gay venues more often than educated ones with marginal statistical significance (P = 0.06). There was no difference in HIV prevalence between the 2 groups: 19.0% (95% CI: 12.6–27.6%) of gay venue attendees and 19.5% (95% CI: 9.9–34.9%) of MSM who never visited a gay venue in the past 12 months were found to be HIV-positive. Among MSM who never visited any type of gay venue, 67.3% (95% CI: 50.3–80.8%) reported being sexually active with men and 0.7% (95% CI: 0.1–3.7%) with women in the past 12 months compared with 94.0% (P < 0.001) and 10.3% (P < 0.01) of gay venue visitors, respectively. A higher proportion of gay venue visitors reported riskier sexual behaviors: 5 or more male partners, 2 or more UAI partners, UAI with secondary partners, and serodiscordant UAI.
Second, we compared the difference between MSM who visited different types of gay venues. Circuit party attendees were much younger than other groups with 47.6% aged 19 to 29 years and only 0.9% aged over 50. Cruisers and circuit party attendees were less educated than gay bar/club and sex club/bathhouse attendees. Although the majority of MSM in any given gay venue were white, white men visited more gay bars/clubs and sex clubs/bathhouses, whereas men of color visited more cruising areas and attended circuit parties. Cruisers reported lower income levels with 28.2% of MSM making less than $20,000 annually. All sex club/bathhouse attendees reported having ever had an HIV antibody test compared with only 88.5% of cruisers and 80.3% of circuit party attendees. Cruisers reported the highest proportion (47.6%) of MSM under age 30 and highest HIV prevalence (40.8%). Gay bar/club attendees and cruisers reported higher rates of having sex with women (8.5% and 14.8%, respectively) than sex club/bathhouse and circuit party attendees (1.7% and 0.7%, respectively). Sex club/bathhouse attendees reported the highest number of male sexual partners and the highest rate of having UAI with secondary partners, whereas circuit party attendees reported the highest rates of 2 or more UAI partners and serodiscordant UAI.
Finally in Table 2, we compared men who visited any gay venue at least once in the past 12 months (the venue sample) with the population sample, which included the venue sample and MSM who did not visit any gay venue in the past 12 months. The results showed that the venue sample had similar HIV prevalence (19.0% [95% CI: 12.6–27.6%] vs. 19.1% [95% CI: 12.8–25.3%]) and slightly higher rates of sex with men (94.0% [95% CI: 88.7–96.9%] vs. 89.6% [95% CI: 84.6–93.1%]), sex with women (10.3% [95% CI: 5.9–17.4%] vs. 8.7% [95% CI: 5.0–14.8%]), 5 or more male sexual partners (33.8% [95% CI: 26.7–41.6%] vs. 28.5% [95% CI: 22.7–35.2%]), 2 or more UAI partners (16.2% [95% CI: 10.7–23.9%] vs. 13.9% [95% CI: 9.0–20.8%]), UAI with a secondary partner (17.6% [95% CI: 13.2–23.1%] vs. 15.0% [95% CI: 11.2–19.8%]), and serodiscordant UAI (12.2% [95% CI: 7.7–18.8%] vs. 10.9% [95% CI: 6.9–16.7%]).
Although there was no statistical difference in HIV prevalence among MSM with different frequency of gay venue visits (Table 3), both bivariate and multivariate logistic regression analysis indicated that gay venue frequent visitors were more likely to engage in high-risk sexual behaviors: 5 or more male partners, 2 or more UAI partners, and UAI with secondary partners.
We further performed multivariate logistic regression analyses to assess whether HIV-positive MSM were more likely to engage in high-risk sexual behaviors controlling for age, education, race/ethnicity, residence, and frequency of gay venue visit. We found that HIV-positive MSM reported higher rates of 5 or more male sexual partners (AOR = 2.50, 95% CI: 1.11–5.88) and 2 or more UAI partners (AOR = 4.76, 95% CI: 1.96–11.11) given the same frequency of gay venue visits.
Our study showed that the majority (83.5%) of MSM living in California visited a gay venue in the past 12 months, with 76.4% of MSM visiting a gay bar at least once. Consistent with another population-based survey,34 we found that MSM who visited gay venues differed from those who did not in sexual risk behaviors. Gay venue attendees were more likely to be younger, men of color, and engage in high-risk sexual behaviors. MSM who did not visit gay venues had little or no chance to be selected in venue-based studies; therefore, results from these studies cannot represent all MSM and are likely to overestimate sexual risk behaviors. The magnitude of overestimation depends on the difference between those who did and did not visit gay venues, and the proportion of MSM who never visited gay venues. Nevertheless, risk estimates from venue-based studies are still useful. Our intervention activities usually target a subgroup of MSM who are at high risk and reachable. Venue-based studies provide useful information to develop appropriate intervention programs for targeted high-risk populations. In addition, although population-based sampling is the epidemiologic gold standard for prevalence measures, population-based surveys are prohibitively expensive to conduct on a frequent basis, so cost considerations preclude relying only on population-based sampling. If we keep our sampling strategy consistent, venue–day–time sampling-based HIV behavioral surveillance can still monitor trends in behavioral change among MSM populations unless a certain MSM group (e.g., high-risk men) frequenting gay venues changes substantially without changing their risk behaviors. When we conduct venue-based surveys, we can better understand the results if we have population-based data on the proportion and characteristics of MSM who do and do not visit gay venues at a local level.
Our study found differences in characteristics and sexual risk behaviors among men who visited different types of gay venues. Circuit party attendees were much younger than the other groups. MSM attending gay bars/clubs and sex clubs/bathhouses were more likely to be white than men using cruising areas or attending circuit parties, although the majority of MSM who visited gay venues were white. Cruisers reported lower income levels, with 28.2% making less than $20,000 annually. All sex club/bathhouse attendees (n = 74) reported having had an HIV test compared with only 88.5% of cruisers and 80.3% of circuit party attendees. Gay bar/club attendees and cruisers reported higher rates of having sex with women (8.5% and 14.8%, respectively) in the past 12 months. Heterosexual transmission of HIV may need to be addressed in any intervention programs designed for them. Sex club/bathhouse attendees reported the highest number of male sexual partners and the highest rate of UAI with secondary partners, whereas circuit party attendees reported the highest rate of 2 or more UAI partners and serodiscordant UAI.
Samples from one particular type of gay venue may not be generalizable to the larger MSM community; together, they provide a more complete picture of characteristics, HIV prevalence, and risk behaviors for the MSM community as a whole. Gay bar/club attendees showed similarity in all aspects (demographic characteristics, HIV prevalence, and sexual behaviors) with the venue sample. Given the similarity in the results and the fact that the majority (91.5%, weighted; 91.3%, unweighted) of gay venue visitors in California were gay bar/club attendees and many MSM (86.3%, weighted; 84.8%, unweighted) visited other gay venues could also be captured in gay bars/clubs, just sampling gay bars/clubs would give a very good venue-based sample and there might not be any need to cover all gay venues.
Our study also demonstrated that frequent gay venue visitors were more likely to engage in risky sexual behaviors. MSM making frequent visits have a greater chance of being enrolled, so HIV behavioral surveillance and studies using venue–day–time sampling would overestimate HIV risk behaviors if no weighting procedure for frequency of attendance is applied to adjust for the possibility of selection. To make this adjustment, the weight is calculated as the inverse of the probability that the person was enrolled during the study. The more frequently a person attends venues in the sampling frame, the lower the weight that person contributes to the estimate. The enrollment probability depends on the person's pattern of attendance at venues included within the study sampling frame, the probability of choosing each venue for sampling within this pattern of attendance, and the sampling fraction obtained at venues where participants were enrolled in the study.28
The sample of our study was representative of sexually active adult MSM in California who self-identified as gay or bisexual, and the results may not be generalizable to a larger MSM community in California and elsewhere. HIV prevalence and HIV-related risk behaviors may differ among men who self-identified as heterosexual but had sex with men.35,36 Studies have shown a high percentage (88–93%) of MSM self-identify as gay or bisexual in California,37,38 so we do not expect that the exclusion of nonself-identified MSM biased our estimates markedly. Not all but some of our findings may be generalizable. MSM who visited different types of gay venues and visited gay venues with different frequencies may differ in sexual risk behaviors in other areas as well, although the degree of difference may not be the same as it is in California. This difference should be taken into account whenever and wherever we conduct venue-based studies.
In agreement with one previous study among young MSM,29 we did not find any association between frequency of gay venue attendance and HIV prevalence. One explanation for this is that HIV-positive MSM may decrease or stop their visits to venues after they receive a diagnosis of HIV infection. The similarity of the HIV prevalence estimate from the population-based sample and the subsample who reported venue attendance may suggest that venue samples can obtain good estimates of HIV prevalence in MSM. We suggest caution in interpreting this result, however, because our results reflect a particular stage of an epidemic now more than 20 years old in MSM in California. The relationship among age, HIV infection, and visiting gay venues may change with time as the population ages further.
In conclusion, MSM who visited different types of gay venues and with varied visit frequency showed marked differences in sexual risk behaviors, and the differences suggest the importance of determining respondents' enrollment probability based on their pattern of venue attendance and applying weighting procedure in data analysis to obtain unbiased estimates in venue-based studies.
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