“…The CHARLS questionnaire inquired about individuals' engagement in 10 social activities throughout the previous month. There were 12 possible answers to this question: (1) interacted with friends, (2) played mahjong, chess, or cards, or attended a community club, (3) assisted family, friends, or neighbors who did not live with them, (4) attended sports, social, or other kinds of clubs, (5) participated in a community-related organization, (6) did voluntary or charity work, (7) cared for a sick or impaired adult who did not live with them, (8) attended an educational or training course, (9) invested in stocks, (10) utilized the Internet, (11) other, or (12) none of these in the last month. Based on the mainstream social participation classification (7,22), in this study, we examined four types of formal social participation: (1) social groups: interacted with friends, (2) hobby groups: played mahjong, chess, or cards or went to a community club; (3) sports groups: went to sports, social, or other kinds of clubs; and (4) community-related organizations: took part in a community-related organization.…”