Transitions and trajectories in frailty states over time: a systematic review of the European Joint Action ADVANTAGE., O'Caoimh, Rónán, Galluzzo Lucia, Rodríguez-Laso Ángel, Van der Heyden Johan, Ranhoff Hylen Anette, Carcaillon-Bentata Laure, Beltzer Nathalie, Kennelly Siobhán, and Liew Aaron , Ann Ist Super Sanita, 2018 Jul-Sep, Volume 54, Issue 3, (2018)