Twenty-five years after the AIDS epidemic was first recognized, men who have sex with men (MSM) remain disproportionately represented in national HIV/AIDS statistics in the United States. Approximately half (47%) of all HIV/AIDS cases diagnosed in 2004 in the 33 states and territories with name-based HIV reporting occurred among men who reported same-sex behavior [1,2].
HIV serostatus disclosure between sexual partners provides a public health benefit. Although disclosure between serodiscordant partners does not necessarily mean that safer sexual behaviors would occur, knowledge of a sexual partner's HIV serostatus can be a motivating force for many to engage in safer sex practices [3,4]. MSM have adopted sexual risk-reduction strategies related to HIV serostatus disclosure. Men may avoid penetrative anal intercourse or use condoms when they have sex with partners of unknown or serodiscordant serostatus [5–10]. Men may also practice serosorting: HIV-positive men preferentially select other HIV-positive men and HIV-negative men select other HIV-negative men as sexual partners for engaging in unprotected anal intercourse (UAI) [11–16].
However, there are many factors that may dissuade HIV serostatus disclosure, especially for persons with HIV, including potential rejection, stigmatization, or loss of privacy. HIV disclosure also requires particular communication skills . Studies of MSM show varied rates of disclosure: 74–89% and 25–41%, respectively, of HIV-positive men disclosed to their primary and secondary partners [18–20]; 92% and 45%, respectively, of HIV-negative men disclosed their HIV serostatus to their primary and secondary partners ; and 63–86% and 34%, respectively, of men knew their primary and secondary partner's HIV-positive serostatus [19,22].
Most of the studies investigating HIV serostatus disclosure and sexual practices among MSM [18–25] have been based on convenience samples and were conducted before the widespread availability of HAART. The ability to obtain a population-based sample of MSM has always been restricted by the prohibitive cost of screening a large number of households to obtain a sufficiently large sample for generalizable estimates. The California Health Interview Survey (CHIS), a random-digit dial survey, interviews more than 50 000 adults on a variety of health topics every other year . The results described here were obtained by taking advantage of the CHIS 2001 sample and the question on sexual orientation to obtain a statewide, population-based sample of MSM. The purpose of this study was to obtain generalizable findings of MSM's knowledge of sexual partner's HIV serostatus and sexual practices, including serosorting, since the era of HAART.
Sampling design and eligibility criteria
CHIS MSM Follow-up Study, conducted from May 5 through June 23, 2002, was a follow-up study to the CHIS 2001 based on a probability sample of MSM living in California. The methodology of the survey and measures to protect human subjects have been previously described in detail . Briefly, the target sample was men aged 18–64 years who self-identified as gay or bisexual in the CHIS 2001 but were screened for same gender sexual behavior in the past 10 years regardless of orientation. Of the 875 men who identified as gay (593) or bisexual (282) in the CHIS 2001, 741 (84.7%) agreed to participate in the CHIS MSM Follow-up Study. No statistical differences were found between the men who agreed to participate and those who did not in terms of age, race, or metropolitan statistical area status. (A metropolitan statistical area is defined by the US Office of Management and Budget as an area that has at least one urbanized area with a population of 50 000 or more .) In our study, participants' residence metropolitan statistical areas were divided into five categories: Los Angeles, San Francisco, other large areas throughout California, smaller areas throughout California, and non-metropolitan statistical area).
Among the 741 participants who gave consent for follow-up, 193 (26.0%) were not reached and 114 (15.4%) were screened out of the CHIS MSM Follow-up Study because they had not had sex with a male in the past 10 years, leaving 434 (58.6%) from the CHIS 2001 eligible for the CHIS MSM Follow-up Study. Of these, 398 (91.7%) completed the 30–45 min interview in either English or Spanish. Forty-four men who were found not to have sex with a male in the past year were subsequently excluded from the analyses, leaving a final sample of 354.
Demographic characteristics and HIV serostatus
Respondents reported their age, race/ethnicity, education, annual income, city/rural area of current residence, length of residency, and the result of their most recent HIV antibody test. Based on our previous study of home testing, in which 100% of self-reported HIV-positive men were confirmed to be positive by laboratory tests , only those in the present study who self-reported as HIV negative or of unknown HIV status were asked to provide a sample for HIV testing using a home urine specimen collection kit (Calypte Biomedical, Berkeley, California, USA). The presence of HIV antibodies was demonstrated by enzyme immunoassay (Calypte Biomedical), and positive results were confirmed by Western blot (Calypte Biomedical).
Sexual risk behaviors and partner's HIV serostatus
Respondents were asked a series of general questions about their sexual behaviors with male partners, including number of male sexual partners overall and the number of partners with whom they had engaged in various sexual behaviors. Respondents were also asked about their sexual behaviors on a partner-by-partner basis, including frequency of insertive and receptive anal intercourse with and without a condom, as well as each partner's HIV serostatus, for their current primary partner and up to three other most recent secondary partners, or for up to four most recent partners if they did not have a primary partner. A primary partner was defined as a male sexual partner whom the respondent was currently in love with or felt a special commitment to (Interviewer: ‘I’d like to ask if you are currently in love with or feel a special commitment to [either/any one] of these men we just talked about?’) . A secondary partner was defined as a male sexual partner whom the respondent was not currently in love with or did not feel a special commitment to. Partner-by-partner information, including knowledge of the partner's HIV status, was used to determine whether UAI occurred with a serodiscordant partner.
Respondents reported if they or their sexual partners had ever injected or currently inject any recreational drugs.
The analyses were limited to the 354 men who reported having sex with men in the past year; of these, 102 (28.8%) reported having sex with primary partners only, 132 (37.3%) with secondary partners only, and 118 (33.3%) with both primary and secondary partners (two men did not report the relationship of their sexual partners). The responses were analyzed separately for men with primary partners (220) and men with secondary partners (250). Because the partner-by-partner questions enabled up to four secondary partners to be captured, and 32% of men in the sample reported five or more male sexual partners in the past year, the analyses were limited to knowledge of secondary partners' HIV serostatus and sexual practices to participants' most recent secondary partner.
The HIV serostatus of primary and secondary partners by respondent's HIV serostatus was analyzed using χ2 tests. Logistic regression models were then developed to identify associations with knowledge of primary or secondary partner's HIV serostatus using crude odds ratio (OR) and adjusted odds ratio (AOR) controlling for age, education, race/ethnicity, income, and respondent's HIV serostatus. Finally, point estimates with 95% confidence intervals (CI) were calculated for sexual practices (sex other than penetrative anal intercourse, 100% protected anal intercourse, serocordant UAI, and serodiscordant UAI) for primary and secondary partners by respondent and partner's HIV serostatus. P values < 0.05 were considered significant.
In the analyses, each study subject was weighted to account for the probability of selection, non-response, and undercoverage. The weighting process occurred in both the original CHIS 2001 study and subsequent CHIS MSM Follow-up Study. In the CHIS 2001, a base weight was computed as the inverse of the probability of selection of the sampled unit, and then the base weight was adjusted to account for additional stages of sampling and non-response to create a final weight for each participant . In the CHIS MSM Follow-up Study, the final weight in the CHIS 2001 for all eligible men who were between 18 and 64 years old and self-identified as gay/bisexual was used as an initial weight. A final full sample weight was then created by adjusting the initial weight to account for two types of non-response: men who said during the CHIS 2001 interviews that they were not willing to participate in a follow-up survey, and men who agreed to participate but were unable to participate in 2002 owing to mobility, physical health, death, and so forth. Eighty replicate weights were also created using the paired Jackknife method, and they were adjusted in the same way as the full sample weight. The analyses were conducted with SUDAAN , which accounts for the complex sample design, and Jackknife method was used to estimate standard errors. All data in this report were weighted unless indicated otherwise.
The weighted and unweighted characteristics of the sample are presented in Table 1. Participants ranged in age from 19 to 65 years, and 16.5% had a graduate degree. The majority (68.8%) of men were non-Hispanic White. Annual income was $80 000 or more for 20.3% of MSM. History of injecting recreational drugs was reported by 6.6% of men. About 16% of men self-reported as HIV positive and 78% as HIV negative.
Knowledge of partner's HIV serostatus
The majority (92.9%) of men with primary partners (220) knew their own HIV serostatus. Overall, 12.1% reported knowing that their primary partners were HIV positive and 74.2% knew that their primary partner was HIV negative (Table 2). That is, 86.3% knew their primary partner's HIV serostatus. No difference was found for knowledge of primary partner's HIV serostatus between HIV-positive (38.6% + 53.2% = 91.8%) and HIV-negative (6.6% + 85.0% = 91.6%) participants. Only 1 of the 10 men with unknown HIV serostatus knew his primary partner's status. Because of the small sample size and poor knowledge of their primary partner's HIV serostatus, 10 men who had a primary partner in the past year but did not know their own HIV serostatus were excluded from further analyses.
Among 250 men with secondary partners, 93.1% knew their own HIV serostatus. No difference was found in the knowledge of secondary partner's HIV serostatus between HIV-positive and HIV-negative men (68.2% versus 65.6%). None of the 10 men with unknown HIV serostatus knew the HIV serostatus of their most recent secondary partner. Because of the small sample size and poor knowledge of their secondary partner's HIV serostatus, 10 men who had a secondary partner in the past year but did not know their own HIV serostatus were excluded from further analyses. Five of these men reported having a primary partner in the past year and were also excluded from further analyses associated with primary partners.
Not surprisingly, HIV-positive men were more likely than HIV-negative men to have sex with HIV-positive partners. Likewise, HIV-negative participants were more likely to report HIV-negative partners. More than one-third (38.6%) of HIV-positive men reported that their primary partners were HIV positive, whereas only 6.6% of HIV-negative men had HIV-positive primary partners (P < 0.01); 27.8% of HIV-positive men reported that their most recent secondary partner also had HIV, whereas only 2.6% of HIV-negative men reported an HIV-positive secondary partner (P = 0.05).
Correlates of knowledge of partner's HIV serostatus
None of the demographic characteristics (age, education, race/ethnicity, and income) or other factors, including respondent's HIV serostatus (HIV positive or HIV negative), sexual risk behaviors (having sex with secondary partner, and five or more male sexual partners), or history of injection drug use, was associated with knowledge of primary partner's HIV serostatus (Table 3).
No significant associations were found between knowledge of secondary partner's HIV serostatus and respondent's demographic characteristics or HIV serostatus. Men with five or more male sexual partners in the past year (AOR, 0.45; P < 0.05), men who ever injected recreational drugs (AOR, 0.25; P < 0.05), and men with a primary partner (AOR, 0.31; P < 0.01) were less likely to know their most recent secondary partner's HIV serostatus.
Table 4 displays the percentage of MSM who reported safer sex, categorized as ‘sex other than anal intercourse’ and ‘100% protected anal intercourse’, and unsafe sex, including ‘serocordant UAI’ and ‘serodiscordant UAI’, over the previous 12 months, by participant and partner's HIV serostatus and partner type (primary and secondary).
Sex with primary partners
With known HIV-positive primary partners, 59.4% of HIV-positive men engaged in safer sex (sex without penetrative anal intercourse or anal intercourse with condoms) and 40.6% had UAI that was serocordant; with known HIV-negative primary partners, 82.8% engaged in safer sex and 17.2% had UAI that was serodiscordant; with primary partners of unknown HIV serostatus, 36.7% engaged in safer sex and 63.4% had UAI, which was also considered to be serodiscordant in our study.
With known HIV-positive primary partners, more than half (57.4%) of HIV-negative men engaged in sex other than penetrative anal intercourse and 27.4% used condoms during anal intercourse, but still 15.2% had serodiscordant UAI with their primary partners; with known serocordant HIV-negative primary partners, about two-thirds (61.8%) of HIV-negative men practiced serosorting (i.e., serocordant UAI) with their primary partners, and the remaining (38.2%) practiced safer sex.
Sex with secondary partners
About two-thirds (67.3%) of HIV-positive men engaged in safer sex and one-third (32.7%) had serocordant UAI with their most recent secondary partners whom the respondent knew were also HIV positive. When the secondary partners were known to be HIV negative, 92.4% of HIV-positive men would practice safer sex, but still 7.6% engaged in serodiscordant UAI, putting the partners at risk of HIV infection.
None of HIV-negative men reported having UAI with their secondary partners who were known to be HIV positive. When men knew their secondary partners were serocordant HIV negative, 79.8% practiced safer sex and 20.3% had serosorting, serocordant UAI.
One of the objectives of our study was to describe knowledge of sexual partners' HIV serostatus among a population-based sample of MSM. We found that 86.3% and 61.5% of MSM, respectively, knew their primary and secondary partner's HIV serostatus. Our estimate of HIV serostatus disclosure for primary partners was similar to the rate found in other studies [18–21] but our estimate for secondary partners was almost double the estimates previously reported [18,21]. In addition to the apparent effectiveness of on-going efforts to promote disclosure of one's HIV serostatus to sexual partners and learn one's partner's HIV serostatus, web dating may play a large role in the increase of serostatus disclosure [33–35]. MSM may learn a secondary sexual partner's HIV serostatus by the profile posted on the Internet; these posting may also specifically request a sexual partner of the same HIV serostatus. The anonymity of the Internet helps men to eliminate the awkwardness of initiating discussions related to HIV serostatus disclosure and the fear of rejection that may occur in face-to-face discussions.
As explained in a previous paper , our weighted and unweighted data generally did not vary greatly, but there were a few notable exceptions. In our sample, the unweighted and weighted estimates for young men 19 to 29 years of age were 9.6% and 21.2%, respectively. Men in these ages are an especially mobile population. As our survey was conducted a year after the original CHIS 2001, loss to follow-up in the interim period accounted for the large effect of weighting in this age group. Probably for the same reason, similarly large increases attributable to weighting occurred among Hispanic men and among men with a high school education or less. The loss to follow-up of this young and highly mobile population suggested that weighted analysis might be more appropriate.
Because of the legal and ethical responsibility related to non-disclosure of HIV-positive serostatus, HIV-positive men may be more likely to report social desirability responses to the interviewers rather than admitting non-disclosure. In an attempt to reduce this bias, we did not directly ask about HIV serostatus disclosure but asked men their sexual partner's HIV serostatus. Studies show that HIV serostatus disclosure was a reciprocal process. Men who asked their partner's HIV serostatus were more likely to disclose their own, and men who disclosed their HIV serostatus expected their partners to do the same . The findings in our study may also provide some evidence of this reciprocal process: men of unknown HIV serostatus were less likely to know their partner's HIV serostatus. (In our sample, only 1 in 10 knew his primary partner's HIV serostatus, and none knew their most recent secondary partner's HIV serostatus.)
There are several other limitations in this study that should be acknowledged. First, in addition to disclosure, our self-reported data are subject to recall and social desirability bias. Second, respondents were asked about their sexual partner's HIV serostatus but were not asked how they obtained the information. Some respondents may have been told directly by their sexual partners, but some may have obtained the information from other sources (e.g., partner's hint, assumption that since partner did not disclose he must be HIV negative, or from other persons) . We were unable to determine how many men in our sample obtained their sexual partner's HIV serostatus through partners' direct disclosure or other means. If respondents were directly told by their sexual partners, we believe that most MSM were receiving their partners' true HIV serostatus, as most HIV-positive MSM neither want to nor intend to transmit the virus [3,4,17], and few if any HIV-negative men want to be infected with the virus. If obtained from non-verbal hints, the information may not always be accurate [38,39]. Third, only 44 HIV-positive men reported having sex with their primary partners, and 45 HIV-positive men reported having sex with their secondary partners in the past year. Such small sample sizes limited our capability to produce precise estimates. Finally, our study was conducted in California and included only MSM who were willing to admit to such behavior. Therefore, the results may not be generalizable to all MSM throughout California or to other regions of the United States.
Among men with a secondary partner in the past year, we found that men with a primary partner were less likely to know their secondary partner's HIV serostatus (OR, 0.37; AOR, 0.31), but no difference was found in their sexual risk behaviors (data not shown). Men with primary partners may not have the communication skills to discuss HIV serostatus with their secondary partners, and/or less frequently use web dating, which many men use to find secondary partners with the same HIV serostatus.
We found that serosorting was not particularly an uncommon practice in this population. Two-fifths (40.6%) of HIV-positive men and three-fifths (61.8%) of HIV-negative men engaged in serocordant UAI with their primary partners, whereas 32.7% HIV-positive men and 20.3% HIV-negative men did so with their most recent secondary partners. The risk of HIV transmission associated with serosorting depends on how recently the two men receive an HIV-negative test result or whether they are forthcoming during discussions related to HIV serostatus. In our sample, 93.2% of MSM had ever had an HIV test, and 35.1% of HIV-negative men received their HIV-negative test results in the past 12 months. Among 75 HIV-negative men who practiced serosorting with their primary partners and 21 men who practiced serosorting with their secondary partners in the past year, 28 (36.7%, weighted; 37.3%, unweighted) and 7 (25.0%, weighted; 33.3%, unweighted) men, respectively, received their HIV-negative test results in the past 12 months. Five men who self-reported as being HIV negative (three) or of unknown status (two) were later tested HIV positive using home urine specimen collection kit. Four of them reported having safer sex with their partners in the past year, but one man reported engaging in ‘serocordant’ UAI with his HIV-negative primary partner and would have unknowingly placed his partner at risk of HIV transmission. The results demonstrated that serosorting did present some risk of HIV transmission, but the risk was low in our sample, which represented sexually active adult MSM in California.
Our study and data from San Francisco may indicate that HIV-negative MSM are increasingly selecting partners known or presumed to be HIV negative [40,41], suggesting an increase in HIV serosorting. One study conducted in Montreal, Canada, also documented an increase in UAI with regular seroconcordant partners . Since serosorting behavior presents lower risk of HIV transmission but equal or higher risk of transmission of other sexually transmitted diseases, the findings provide cautious optimism that the continuing rise in overall unprotected sex and sexually transmitted diseases observed in recent years among MSM population may not necessarily translate into concurrent increases in HIV incidence [40,41,43–47].
In conclusion, MSM had considerable levels of knowledge of their sexual partner's HIV serostatus, and serosorting was not an uncommon practice, especially within primary partners. Since serosorting (i.e., serocordant UAI) presents significant lower risk of HIV transmission, and an increase over time in the percentage of men reporting UAI does not necessarily mean an increase in the level of sexual risk taking, we recommend that researchers separately report serocordant and serodiscordant UAI in their behavioral studies.
The study would not have been possible without the extensive cooperation of the respondents who were willing to participant in the project. The authors would also like to 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.
Sponsorship: 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.
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