The impact of social activity on cardiovascular disease risk among middle-aged and older adults in China: a nationwide cohort study based on the CHARLS database - Wu, Yingting; Cheng, Qi; Song, Haiyang; Gong, Xinyue; Wang, Sihan; Xu, Kehui; Qin, Lei; Cheng, Jing; He, Fei (Frontiers in Public Health, 2025)