Association between plant-based diets and depression in older adults with heart disease: the mediating role of sleep disturbances - Yu, Yaqun; Cheng, Yueying; Cheng, Nan; Zhang, Jie; Xu, Qitao; Wang, Yawen; Zhou, Wei; Yan, Chao; Li, Huiqiong; Gong, Zhiyun (Frontiers in Nutrition, 2025)