Corrigendum: Association Between Metabolic Syndrome and Mild Parkinsonian Signs Progression in the Elderly - Peng, Zeyan; Zhou, Rui; Liu, Dong; Cui, Min; Yu, Ke; Yang, Hai; Li, Ling; Liu, Juan; Chen, Yang; Hong, Wenjuan; Huang, Jie; Wang, Congguo; et al. (Frontiers in Aging Neuroscience, 2021)