Association between chronic pain and cognitive frailty among middle-aged and elderly individuals: evidence from the China Health and Retirement Longitudinal Study - Li, Tianjiao; Li, Lingxuan; Xie, Hongyang; Ping, Rongyu; Guo, Yane; Li, Dongmei; Zhang, Yuwei; Bai, Xiujuan; Sun, Bo (Frontiers in Aging Neuroscience, 2024)