Curvilinear association between cardiometabolic index and depressive symptoms in individuals aged 45 and older: a cross-sectional study of CHARLS - Han, Sibo; Zhang, Yingqi; Wu, Bingxin; Chen, Qingyun; Han, Zhengyuan; Chen, Jingmin; Li, Peishan; Xu, Meimei (Frontiers in Public Health, 2025)