Social network analysis of geosocial networking among men who have sex with men in Zhuhai, China

Background Social media platforms are important spaces for social and sexual networking among men who have sex with men (MSM). However, limited research has examined structural changes in MSM digital social networks or the contribution of different user roles in maintaining network connectivity. This study aims to investigate structural changes and user dynamics in an online MSM network to inform tailored digital public health interventions. Methods We constructed directed social networks among MSM in Zhuhai, China, using large-scale Blued platform data collected in 2021 and 2024. Users were represented as nodes, and follow relationships were represented as directed edges. Key network metrics, including degree distribution, reciprocity, assortativity, community fragmentation and attribute-based homophily, were analysed to identify weak links and structurally important users. Results The analysis included 9409 valid users in 2021 and 8890 in 2024. The network was significantly sparser and more fragmented, with edge density halving and 70.91% of detected communities containing only two users in 2024. Average degree dropped from 19.52 to 8.00, whereas degree assortativity decreased from −0.0580 to −0.1482, indicating increasing disassortative mixing. Despite reduced platform engagement, younger, versatile, and highly active boundary and common users remained important for sustaining inter-community connectivity. Conclusions From 2021 to 2024, the MSM network on Blued became more fragmented, disassortative and heterogeneous. These changes may constrain health-message diffusion. Network-informed strategies targeting central and bridging users, while improving access for peripheral users, may enhance equitable information dissemination among MSM communities.