To explore the mechanism of online social participation affecting the health of the elderly through online social support and online risk exposure, and to explain the regulatory role of intergenerational cohabitation.

The data of online social participation and health status of people over 60 years old in Henan Province in 2023 were selected, and the moderated mediating effect, moderating effect, and regulated mediating effect were tested with the moderated intermediary effect model in PROCESS4.0 macro program.

Online social participation positively affected online social support (β=1.734, P < 0.001) and online risk exposure (β=1.453, P < 0.001). Online social support positively affected physical health (β=0.183, P < 0.001) and mental health (β=0.398, P < 0.001). Online risk exposure negatively affected physical health (β=-0.490,P < 0.001) and mental health (β=-0.598, P < 0.001). The interaction between online social participation and intergenerational cohabitation negatively affected online risk exposure (β=-0.784, P < 0.001), and the mediating effect differences between intergenerational cohabitation group and non-intergenerational cohabitation group were 0.384 (95%CI: 0.146-0.678) and 0.469(95%CI: 0.205-0.778) respectively on the physical/mental health path of online social participation.

Online social participation has a positive impact on the physical and mental health of the elderly through online social support, and a negative impact on physical and mental health through online risk exposure. Intergenerational cohabitation weakens the positive impact of online social participation on online risk exposure and the intermediary effect of online risk exposure.