Syndemic factors tend to co-occur and increase the risks of condomless anal intercourse (CAI), multiple sexual partners (MSP) and HIV vulnerability among men who have sex with men (MSM). This study aimed to test the synergistic effects of syndemic factors on HIV risk and to further explore the moderators between syndemics and HIV risk among Chinese MSM. A cross-sectional study was conducted to recruit MSM in Guangzhou to collect data on syndemic factors (depression, intimate partner violence, childhood sexual abuse [CSA], alcohol, and rush popper use before anal sex). The relative excess risk due to interactions (RERIs) was calculated to test the synergy in adjusted regression models. A moderated analysis was conducted to test the buffer effects of potential resilience factors (education and income). Among the 976 included MSM, individuals experiencing more syndemic factors were more likely to have CAI (odds ratio [OR]= 1.26, 95% confidence interval [CI] 1.11-1.44), MSP (OR= 1.33, 95% CI 1.16-1.52), and HIV infection (OR= 1.46, 95% CI 1.12-1.90). RERIs showed a synergy of depression and rush popper use prior to sex for MSP (1.17, 95% CI 0.03-2.03) and CSA and rush popper use prior to sex for HIV infection (1.72, 95% CI 0.05-3.43). However, no significant association was found for the interaction between the number of syndemic factors and education or income. Our findings support the synergy approach in syndemic studies and highlight the need for comprehensive and multifactorial intervention strategies on sexual health of MSM. Future studies are needed to identify potential resilience factors among Chinese MSM.
Keywords: HIV infection; Men who have sex with men; Sexual orientation; Sexual risk behaviors; Syndemic.