How Gait Influences Frailty Models and Health-related Outcomes in Clinical- and Population-based Studies: A Systematic Review Ilaria Bortone 1 , Rodolfo Sardone 1 , Luisa Lampignano 1 , Fabio Castellana 1 , Roberta Zupo 1 , Madia Lozupone 1,2 , Biagio Moretti 3 , Gianluigi Giannelli 4 and Francesco Panza 1,2 1 Population Health Unit - "Salus In Apulia Study”, National Institute of Gastroenterology "Saverio de Bellis", Research Hospital, Castellana Grotte, Bari, Italy 2 Neurodegenerative Disease Unit, Department of Basic Medicine, Neuroscience, and Sense Organs, University of Bari Aldo Moro, Bari, Italy 3 Orthopaedics and Trauma Unit, Department of Basic Medicine, Neuroscience, and Sense Organs, University of Bari Aldo Moro, Bari, Italy 4 Scientific Direction, National Institute of Gastroenterology "Saverio de Bellis", Research Hospital, Castellana Grotte, Bari, Italy