Number of chronic diseases and cognitive function among the elderly in China: a moderated mediation model - Feng, Xiaoling; Peng, Jie; Cao, Xiaoying; Lai, Lichong; Huang, Dongmei; Tao, Pinyue; Pan, Xiao; Pan, Qini; Fan, Dejing; Lu, Shuyu; Li, Caili; Pan, Yanfei; et al. (Frontiers in Psychology, 2025)