  Background: Accurate survival time estimates aid end-of-life medical
decision-making. Objectives: Develop an interpretable survival model for
elderly residential aged care residents using advanced machine learning.
Setting: A major Australasian residential aged care provider. Participants:
Residents aged 65+ admitted for long-term care from July 2017 to August 2023.
Sample size: 11,944 residents across 40 facilities. Predictors: Factors include
age, gender, health status, co-morbidities, cognitive function, mood,
nutrition, mobility, smoking, sleep, skin integrity, and continence. Outcome:
Probability of survival post-admission, specifically calibrated for 6-month
survival estimates. Statistical Analysis: Tested CoxPH, EN, RR, Lasso, GB, XGB,
and RF models in 20 experiments with a 90/10 train/test split. Evaluated
accuracy using C-index, Harrell's C-index, dynamic AUROC, IBS, and calibrated
ROC. Chose XGB for its performance and calibrated it for 1, 3, 6, and 12-month
predictions using Platt scaling. Employed SHAP values to analyze predictor
impacts. Results: GB, XGB, and RF models showed the highest C-Index values
(0.714, 0.712, 0.712). The optimal XGB model demonstrated a 6-month survival
prediction AUROC of 0.746 (95% CI 0.744-0.749). Key mortality predictors
include age, male gender, mobility, health status, pressure ulcer risk, and
appetite. Conclusions: The study successfully applies machine learning to
create a survival model for aged care, aligning with clinical insights on
mortality risk factors and enhancing model interpretability and clinical
utility through explainable AI.
