This is the first and largest online cohort study constructed and implemented through a GSN app globally that reports HIV incidence and its correlates. We add to current literature[14, 15, 40–45] by providing more robust estimates of HIV incidence, especially to the limited literature on app-using MSM. Using this innovative methodology of GSN apps to maintain a cohort has advantages of reaching high-risk MSM and overcomes barriers related to fear of stigma and discrimination associated with offline cohort studies. Moreover the app-assisted questionnaire may improve the data quality of sexual and highly stigmatized behaviors research among MSM. Data quality does not only depend on the accurate recall of facts but also depends on the degree of peoples’ self-disclosure, which is commonly influenced by an individual’s inherent need to create and maintain favorable impressions of oneself in the eyes of others. Therefore, MSM tend to misrepresent their true behaviors to avoid the stigma of homosexuality and the resulting discrimination in research with traditional methods. A bulk of studies demonstrated that increased self-disclosure of sensitive information were found with decreased personal interactions with an interviewer[47, 48]. We conducted the research using a popular GSN app that is trusted by Chinese MSM; and surveys could be completed using the participants’ own smartphone, avoiding face-to-face interaction with research or healthcare staff. This strategy contributed to the acceptability of the study and consequently low drop-out rate.
The HIV incidence we observed was 3.47/100 person year (95%CI 2.37–4.57), which is lower than 5.36/100 person year (95%CI 2.19–8.53) reported in a 2011 study and 6.0/100 person year (95%CI 4.2–8.4) reported in a 2012 study. After 2012, there was no other cohort reporting HIV incidence among MSM in Beijing. Considering the large 95%CI of the incidence rates reported by these former cohort studies due to their smaller sample sizes (348, 699), the HIV incidence rate we estimated was not statistically significantly different from these studies from 2011 and 2012, which might indicate that despite various HIV prevention interventions, HIV incidence among MSM in Beijing has not significantly declined in recent years.
The factors associated with HIV seroconversion in our study were mostly consistent with other literature. Having multiple sexual partners as a risk factor is consistent with other studies from Beijing, even independent of condom use during sex[42, 43]. The number of sexual partners is widely recognized as a predictor of the likelihood of acquiring STIs, including HIV. Reporting multiple sex partners is high among GSN apps using MSM in China  and other countries[51, 52]; 37.2% of our participants reported having two or more sex partners in the preceding 6 months. Carrying their smartphone with the global positioning system imbedded app at all times, GSN smartphone app users could quickly and conveniently locate potential sex partners nearby, leading to more casual sex,greater number of sex partners༌thus facilitate app users engaging in unprotected anal sex[53, 54]. We found consistent condom use for anal sex reduced the probability of HIV incidence with hazard ratio of 0.27, which was inconsistent with other studies from MSM in Beijing with smaller sample sizes (348, 574–769). This inconsistency may be due to their smaller sample size restricting their power to detect the independent effect of condoms use[42, 43].
Our study also found that 48.3% of our participants were not aware of the HIV status of their partners; though only 4.5% reported have HIV positive partners, sex with HIV positive partners was a significant predictor of HIV incidence. Previous research demonstrated that GSN smartphone app users were more likely to have a greater number of sexual partners known to have HIV and other STIs; this increases their risk for HIV and STIs acquisition or transmission, compared with MSM who seek sex partners using other ways[56, 57]. Though seroadaptive practices (choosing HIV-negative partners or practicing only insertive anal sex with potentially discordant partners) among HIV-negative MSM is associated with a lower HIV incidence, the low disclosure of a partners’ HIV status have increased the HIV transmission among GSN smartphone app using MSM. Further, among MSM in China, the lifetime HIV testing rates remains at only 47%, and the annual HIV testing rates is even lower (38%), therefore 62 to 87% of MSM living with HIV remains undiagnosed[60, 61].
We also found that MSM exclusively practicing insertive anal sex had a reduced risk of HIV (HR = 0.23), consistent with other studies[62–65]. In the United States, men who only had insertive anal sex had a lower risk of acquiring HIV (HR = 0.55, 95%CI 0.36–0.84). Though some studies found sociodemographic characteristics like age and immigration status as correlates of HIV infection[43, 66–69], we did not find the same associations. Some reasons might be due to different sampling methods[5, 70–72], different sample sizes[5, 70–72] and geographical difference[5, 70, 72].
Though China has scaled up its responses to the HIV pandemic, our findings suggest that the HIV incidence among MSM in Beijing has not decreased. The possible reason may be the patterns of HIV risk behaviors among MSM are changing with the use of the Internet and GSN smartphone apps as the main tool for partner seeking, while efforts to control HIV transmission in this population still focused on individual-level behaviors, such as consistent condom use and regular HIV testing. Many studies demonstrated the importance of contextual factors–such as where MSM meet their partners–may have on the risk of HIV transmission[51, 74–76]. The GSN smartphone apps could facilitate partner seeking, thus result in more casual and unprotected sex. Moreover, with the shift of partner seeking behaviors from in person venues to GSN apps, traditional intervention strategies designed for gay-centered venues, such as gay bar and public bathroom, may not be effective in reaching MSM anymore. Our findings suggest that further strategies and implementation of new interventions are urgently needed to curb the HIV epidemic among MSM in China.
The main strength of our study is in its innovative use of GSN app to construct and maintain a cohort of MSM in China. Though there are studies among MSM recruited using social networking applications in China, the majority of them are cross-sectional studies[77, 78]. To our best knowledge, this study is the first cohort study constructed and implemented through a GSN app globally. With fear of stigma, MSM prefer to access information about HIV and testing services through the Internet because the process is convenient, anonymous and private[79, 80]. With the development of network technology and the spread of Internet access, more MSM seek health services, especially HIV-related services, through the Internet[81, 82]; there is great potential for future use of GSN app in HIV research and intervention. In addition, we constructed an open cohort to estimate HIV incidence among app-using MSM, participants could complete a follow-up whenever they visited the GSN app for an HIV test, and new participants were enrolled whenever they visited the app to have an HIV test. Therefore, we obtained a cohort with participants staying natural and with better representativeness.
Our study is subject to several limitations. First, our study population were mostly young men who used social network application for partner seeking and health services, so our findings are not generalizable to MSM who do not use social network applications. Second, some participants might test for HIV in other places but not in Blued sites. For example, they could directly go to the CDC to get an HIV test, therefore the HIV incidence we calculated may be underestimated.
Though China has scaled up its responses to the HIV epidemic, the HIV incidence among MSM has not significantly decreased. Given the pervasive use of GSN smartphone app among MSM and the changed patterns of sexual risk behaviors, further strategies and implementation of new interventions are urgently needed to curb the HIV epidemic among MSM in China. Our study demonstrated the strength of GSN smartphone app in conducting research among MSM, indicating that tailored interventions based on GSN smartphone app using can be more targeted and individualized, therefore may provide us with novel opportunities to decrease HIV infection and transmission of MSM.