Exploration of the population size of men who have sex with men in Hainan colleges: A cross-sectional study based on geographical social network App.

Men who have sex with men (MSM) have historically been a high-risk group for sexually transmitted diseases. In Hainan, the incidence of HIV and syphilis among MSM has increased rapidly. Additionally, there is a growing number of young students being diagnosed with HIV, with MSM identified as the primary demographic affected. However, the size and distribution of the MSM population within colleges and universities in Hainan Province remains unknown. In this study, the Blued App was employed to collect data on users within Hainan colleges and universities from May 9 to May 18, 2023. Using the users information and questionnaire survey data, we applied the multiplier method to estimate the population size of student MSM. Multivariate and geographic density analyses integrating survey data were conducted to identify regional disparities. A questionnaire survey revealed that 89.28% of student MSM reported using the Blued App, and 76.00% of the individuals utilized it for seeking sexual partners. The estimated population size of MSM in colleges across Hainan Province was 3504 (95%CI: 3464-3544), with Haikou and Sanya identified as hotspots. The proportion of active users was 33.13% (860/2596). Notably, Danzhou and Wenchang, relatively small urban areas with limited Blued registrants, exhibited high proportion of active users (42.22% and 41.30%). These findings suggest that particular attention should be directed towards sexual health education, and sexually transmitted disease surveillance in specific colleges.