External validation of the Walter index for posthospitalization mortality prediction in older adults - Avelino-Silva, Thiago J; Lee, Sei J; Covinsky, Kenneth E; Walter, Louise C; Deardorff, W. James; Boscardin, John; Campora, Flavia; Szlejf, Claudia; Suemoto, Claudia Kimie; Smith, Alexander K (JAMA network open, 2025)