Using data from a survey on the use of online social tools by mid-aged and older adults in 2021, this paper investigates the relationships between the variety, relationship types, and activity level of online communities, and social networks of mid-aged and older adults by using the structural equation modeling. The study found that the mid-aged and older adults had better relationships with their relatives and friends as the variety of online communities increased. Strong and sub-strong tie groups could promote family and friend networks, respectively, while sub-weak and weak tie groups could promote both types of networks. Moreover, the higher the activity in the online communities, the greater the promotion of their friend networks. Findings promote the understanding of changes in the social network in the internet era. Online communities break through the physical distance in the traditional differential mode of associations by enhancing family relations, strengthening and expanding friend relations horizontally, and helping restore interrupted friend relations vertically. The breadth and depth of the social network of mid-aged and older adults have been developed through online communities.

This study uses data from the 2018 China Longitudinal Ageing Social Survey to explore patterns of older adults' social engagement by latent class analysis. Based on their participation in personal life domain (i.e. learning and communication, personal recreation, working, and volunteering) and family life domain (i.e. caring for parents, caring for grandchildren, and caring for children), four patterns are discovered, including Personal-Family Balanced Activity (P-F), PersonalCentered Activity (P-C), Family-Centered Activity (F-C), and Low Activity. Linear regression analysis reveals that Low Activity are associated with the lowest social adaptation, followed by F-C Activity, while P-C and P-F Activity achieved the best scores and showed no statistical difference. Moreover, urban-rural differences are found in the relationships between social participation patterns and social adaptation. The results suggest that we should protect the social participation rights of older adults, enrich the ways and contents of social participation, and balance their personal life with family life to enhance their abilities to adapt to the social development and changes.

Community governance needs to engage the elderly under the background of population ageing. Based on the theory of person-environment fit, this paper explores the influence of institutional capacity and personal preference on the participation of the elderly in community governance activities in Beijing by using data from 2019 Beijing Social Governance in Ageing Society Survey. The results show that 67.36% of the elderly have a willingness to participate in community governance activities while the actual participation rate is rather low. Institutional capacities of community organizations are barely satisfactory and gaps exist from the needs of the elderly. Better institutional capacities are significantly associated with higher participation of the elderly in community governance activities. In addition, the elderly's preference for the institutional capacity has a moderating effect on the aforementioned relationship. In order to reduce the constraints of institutional barriers on the participation of the elderly, priorities should be given to the abilities valued by the elderly when community organizations carry out community governance activities with limited resources.