Sexually transmitted diseases (STDs) including syphilis, gonorrhea, and chlamydia continue to be a significant cause of morbidity in the United States.1 More than 1.9 million cases of syphilis, gonorrhea, and chlamydia were reported to the Centers for Disease Control and Prevention in 2015, and national estimates predict that more than 20 million new infections occur each year.1 Despite advances in screening and treatment, STDs continue to have a disproportionate impact on gay, bisexual, and other men who have sex with men (MSM).1 In 2015, MSM accounted for 60% of all syphilis and 42% of gonorrhea cases, a 13% and 15% increase from 2014, respectively.1,2 Among MSM, behaviors such as condomless anal intercourse (CAI), engaging in casual or anonymous sex, and having multiple concurrent partners may increase the risk for STDs.1,3,4 Overlapping social and sexual networks are also associated with higher rates of STDs among MSM.1
Use of websites and geosocial networking mobile applications (apps) used to meet sex partners (i.e., “hookup sites”) may also lead to increased risk of infection with HIV and other STDs among MSM.5,6 Although websites and apps differ in architecture and how communication between users takes place, many share the primary purpose of facilitating sexual encounters.3,5–8 The MSM are up to 7 times more likely than non-MSM to have sex with a partner they met online,3 and an estimated 3 to 6 million MSM meet sexual partners worldwide using Internet-based technology.3,8 Research demonstrates that MSM who use hookup sites to meet sexual partners are more likely to engage in higher-risk behavior than men who do not meet partners online.5,6,8,9 Hookup site users may test less often for HIV/STDs,10 have higher rates of CAI,11 and have an increased rate of STDs.6,12 Because hookup sites represent a virtual risk environment for STDs, understanding the demographics and behaviors of men who meet partners on these sites can facilitate development and targeting of effective public health promotion messages.
One approach to evaluating sexual networks among MSM is social network analysis (SNA). The SNA describes the ties among network members (actors) and analyzes characteristics that influence disease transmission. It has previously been used to identify sexual networks of MSM and STD transmission.4,13–16 Specifically, SNA can be used to map where MSM meet sex partners by delineating “affiliation networks.” Although sexual networks depict linkages of individuals and their direct sexual contacts, affiliation networks represent connections between individuals and the venues where they meet sexual partners.14,17,18 The probability of a connection is higher among MSM who use the same venues for partner recruitment, but sexual contact among members of an affiliation network is not guaranteed and 2 venue affiliates with the same STD may not be epidemiologically linked.18 However, by linking MSM to specific venues, SNA can evaluate which venues may be “central” to the network (i.e., have the most connections) and which venues may be associated with testing positive for an STD.14 Previous network studies have focused on the role of physical venues (bars, bathhouses, sex parties, etc.) in facilitating the spread of STDs among networks of MSM.17,19 Internet venues have been found to have higher degrees of centrality (i.e., more connections to individuals in a network) than non-Internet venues,17,19 and clusters of interconnected venues may play pivotal roles in their potential for transmitting disease throughout a given network.19–21 However, few studies have used this approach to evaluate online hookup sites and STD diagnoses.13,18,19 This study describes the affiliation networks of online hookup sites among MSM and investigates the relationship of these networks with testing positive for an STD.
The study was conducted between October 2014 and January 2017 at the Rhode Island STD Clinic, the only publicly funded STD clinic in the state. The clinic serves approximately 3000 patients per year, one third of whom identify as MSM. Men who reported having sex with another man in the past 12 months were offered enrollment into the study. Patients with multiple clinic visits during the study period were only eligible to participate once. A one-time, cross-sectional demographic and behavioral assessment was performed. Sociodemographic data collected included age, race, ethnicity, education level, income, and insurance (public/private/none). Behavioral data collected included number of male and female sex partners in the past 12 months (inclusive of oral, anal, and vaginal intercourse), cumulative number of lifetime partners, drug use, and condom use. Participants were asked where they had met sex partners in the past 12 months, choosing from an extensive list of local sites such as bars and clubs, gyms, bathhouses, sex venues, and parking/cruising sites, as well as virtual venues including hookup sites. Data were also reviewed on clinical outcomes, including the results of testing for syphilis and pharyngeal/rectal/urethral chlamydia and gonorrhea. Extragenital tests for chlamydia and gonorrhea were collected by self-performed swabs, which have demonstrated sensitivity and specificity comparable to physician-collected specimens.22 Nucleic acid amplification testing was used to detect presence of chlamydia or gonorrhea in urethral and extragenital specimens.22
χ2 test and Fisher's exact test were used to assess differences in sociodemographic and risk behavior differences between groups. A 2-sided P value of less than 0.05 was considered statistically significant. Bivariate regression models identified sociodemographic and risk behavior factors associated with meeting partners online and having a positive STD diagnosis, and assessed the association between specific hookup site use and a positive STD result. Multivariable logistic regression determined the relationship between testing positive for an STD and meeting sex partners online. Model 1 and all subsequent models were a priori adjusted for age, race, ethnicity, income, and education level. Model 2 investigated the association between STD results and use of hookup sites to meet sex partners. Additional behavioral risk factors were adjusted for in Model 3. All statistical analyses were completed using R statistical software version 3.3.2.
A venue-based, 2-mode affiliation network analysis was performed to examine the linkages between MSM testing positive for an STD and use of hookup sites to meet sexual partners. A person-hookup site matrix was transposed and multiplied by itself to create a sexual affiliation network (i.e., V = (AT)A).19,20 Core hookup sites, the mathematically defined most centrally and densely connected sites within the network structure, were identified by core-periphery analysis. UCINET 6 and NETDRAW were used for network centrality analysis and visualization.23 The ethics approval and research activities in this study were approved by The Miriam Hospital Institutional Review Board.
Demographics and Behaviors
A total of 415 MSM completed the demographic and behavioral risk assessment. The mean age of participants was 31 years (range, 17–81 years); 36% were nonwhite, 18% identified as Hispanic/Latino, 50% held a college degree or higher, and 80% were insured (Table 1). A total of 104 (25%) tested positive for an STD. More than three quarters of the population (78%) reported meeting a sex partner online in the last 12 months. Compared with MSM who were tested negative, men who were diagnosed as having an STD were more likely to use alcohol 2 or more times a week (47% vs. 35%) and report popper (44% vs. 25%) and methamphetamine (14% vs. 7%) use in the last 12 months (all P values < 0.05). Other behaviors were not associated with being diagnosed as having an STD.
The MSM reported meeting partners more frequently online compared with other venues (Table 2). Men who met partners online were more likely to have sex partners of the same gender rather than partners of different genders as compared with men who did not meet partners online (P < 0.01). Overall, MSM who met partners online were more likely to be white, have more than 10 lifetime sexual partners, and use poppers and other nonpopper, nonmarijuana drugs (Table 1). Use of Grindr was similar between white (76%) and nonwhite (92%, P = 0.20). The MSM who used Scruff were more likely to be white (42%) than nonwhite (23%, P = 0.03). In contrast, nonwhite MSM were more likely to use Adam4Adam (25% vs. 15%, P = 0.04) and Jack'd (24% vs. 13%, P = 0.01).
Most men (71%) who met partners online used more than one site to meet sex partners, using an average of 2.3 sites (range, 0–9). The MSM who used hookup sites also had twice the number of sex partners in the previous year (an average of 12.4 partners/year) compared with men who did not meet partners online (an average of 6.1 partners/year, P < 0.01). Grindr was the most commonly reported online site used, with 78% of MSM who used hookup sites reporting meeting sex partners on this site in the last year (Table 3), including 100% of hookup site users diagnosed as having gonorrhea (Fig. 1). Scruff was the only online hookup site to be associated with testing positive for an STD (P < 0.05), with 34% of Scruff users receiving an STD diagnosis (Table 3).
In the multivariable analysis, those who earned an income in the range of $12,000 to $29,000 (adjusted odds ratio [aOR], 2.38; P < 0.05) and those who held a college degree or higher (aOR, 2.15, P < 0.05) had higher odds of testing positive for an STD (Table 4). Use of Scruff to meet sexual partners was also associated with testing positive for an STD (aOR, 2.16; P < 0.05). Higher frequency of alcohol consumption (aOR, 2.87; P < 0.01), crystal meth use (aOR, 4.49; P < 0.05), and lower frequency of condom use (aOR, 2.30–3.67; P < 0.05) were all behaviors associated with testing positive for an STD (Table 4).
Affiliation Network Analysis
The 2-mode affiliation network of MSM who met partners online and tested positive for a given STD is depicted in Figure 2. Each line represents a connection between an individual and a hookup site used to meet sex partners. The network rendered a diameter of 3.0, indicating that any one individual was only 3 degrees of separation from any other individual in the network. There were no disconnected substructures of linked users or sites separate from the larger network depicted. The sexual affiliation network displayed in Figure 3 represents strength of ties (calculated as sum of cross products) connecting online hookup sites to each other by shared MSM users who tested positive for an STD. The network centralization was 0.21, expressing low variability in centrality between sites, meaning that many sites influenced connections in the network. K-core analysis evaluates network organization, measuring how network members are interconnected into subgroups, wherein subgroup members are interlinked to at least k other sites in the group. The output resulted in an 8-core maximal subgroup (Fig. 3), illustrating the most cohesive regions of the network and suggesting that Black Gay Chat, Mister, Jack'd, Bareback.com, and Recon are less connected sites. The affiliation network typified core/periphery structure, composed of several highly connected sites occupying the center of the network, encircled by a larger number of peripheral sites with fewer connections to each other than those in the center. Core/periphery analysis identified Scruff and Grindr as the network's densely connected central core. Among the 84 MSM with a positive STD result who met partners online in the past year, 91% reported meeting a sex partner on Scruff or Grindr.
This study is among the first to evaluate online hookup sites and STD transmission networks among MSM. Use of online hookup sites to meet sexual partners is a common practice among MSM. More than three quarters of individuals presenting for screening used at least one hookup site. Both individual-level risk behaviors and network-level structure were found to have an impact on STD diagnoses. Similar to other studies, we found that MSM who tested positive for an STD were more likely to have a lower income, have higher alcohol consumption, use methamphetamines, and report less frequent condom use. Although disparities among race and STD diagnosis are well documented,1 no difference between STD diagnosis (any, gonorrhea, chlamydia, syphilis) and race was noted in this cohort. However, certain sites were associated with higher use among different racial groups. In addition, specific online hookup sites were also found to be central components of affiliation networks among MSM (Grindr and Scruff) and were associated with a greater likelihood of testing positive for an STD (Scruff). These data suggest that sexual networks within the context of specific online hookup sites may facilitate STD transmission among MSM.
Grindr and Scruff, the 2 core hookup sites that accounted for the most connections among MSM, are both apps that use a smartphone's internal global position system to identify other users in close proximity. Such apps are commonly used by men for the purposes of meeting other men and not always for the purposes of having sex. Grindr was first launched in 2009 with significant and substantial uptake since its release. Previous studies demonstrate that individuals who meet sexual partners on Grindr had greater odds of contracting both gonorrhea (aOR, 1.25) and chlamydia (aOR, 1.37) compared with individuals who did not meet partners online.6 Additional research has demonstrated that men who meet partners on hookup sites engage in behaviors associated with HIV/STD transmission.8,9 Our prior work demonstrates that a significant number of those that are newly HIV diagnosed have met partners online.3 This study expands on this existing literature to investigate the central nature of specific online hookup sites and their association with STD diagnoses.
Given the extensive use of online hookup sites among MSM to meet sexual partners, these sites offer an ideal approach for health promotion and HIV/STD prevention messaging. For example, this study demonstrates that most MSM who are diagnosed as having an STD, including 100% of men who tested positive for gonorrhea, met partners on Grindr. Although no causality can be inferred between using online hookup sites and STD transmission, this study suggests that once an STD (i.e., gonorrhea) enters the network of men using a specific site, it may be transmitted among a number of users. Given that the type of hookup sites may vary from one region to another, it is important to determine specific hookup sites used in a given community. HIV/STD prevention and outreach on these sites offer an ideal public health opportunity, and evidence supports that it is feasible and acceptable to reach MSM through hookup sites for HIV/STD testing,24–26 prevention and outreach,24–27 and partner notification services.26,28 Given the limited resources available to STD prevention and public health institutions, cost of advertising on hookup sites has been a limiting factor to effective health promotion on these sites.3 Some apps (e.g., Scruff) now offer geo-targeted advertising at no cost for public health nonprofit organizations. Using existing culturally sensitive messaging that has been developed may also help mitigate costs (bhocpartners.org). Given the increasing burden of STDs among MSM, additional efforts are needed for HIV/STD prevention and health promotion messaging on hookup sites used by MSM to meet sexual partners. Multiple and overlapping site use was common among men in our affiliation network. The prominence of Grindr and Scruff in the network demonstrates that additional advertising on peripheral sites may be redundant, because 9 in 10 MSM with a positive STD result who met partners online used either Grindr or Scruff. Interventions that promote education and awareness of HIV testing and other prevention interventions may be most cost-effective and have the highest impact when focused on these “core” sites. However, it is unknown whether targeting these core sites in the network would lead to improved outcomes. Visualization of sexual affiliation networks and core online hookup sites can help guide public health institutions' outreach and interventions, and further study is needed on how effective these strategies are.
The study also found that specific risk behaviors may also contribute to STDs. Notably, use of methamphetamines in the past 12 months was a significant risk factor for a positive STD diagnosis. This may compound the risk among MSM who meet partners online. Individuals may disclose their preferences for using methamphetamines or other drugs on their online profiles (often coded as “parTy and play” or “PnP”). These men represent a group at especially high risk of STD acquisition, which may lead to other behaviors such as CAI and multiple sex partners.29 Many SNA theories postulate that persons with elevated risk levels tend to belong to the same networks,7,14,30 warranting further study into how methamphetamine use may impact STD transmission risk among MSM who meet partners online.
This study is subject to several limitations. Individuals self-reported venues where they had met partners but did not name the partners met at that venue, therefore limiting the ability to evaluate the spread of disease throughout the entire network. This study sampled men presenting for testing at a single STD clinic in a specific region which may limit generalizability. The potential for information bias in the study was minimal, as a standardized questionnaire was issued to collect survey information and validated diagnostic tests were used to screen for STDs. To limit selection bias, all MSM who presented for STD screening or treatment at the clinic during the study period were offered enrollment into the study. However, information on refusal rate was not collected. Importantly, the study relied on cross-sectional data analyses and could not determine causation between using hookup sites and being diagnosed as having an STD.
In Rhode Island, most MSM presenting for HIV and STD screening services meet partners online. Two apps accounted for the overwhelming majority of hookup sites used by these men. A large proportion of MSM with recently diagnosed STD could be reached with health promotion messaging on Scruff and Grindr.
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