A new four-factor functional frailty index (mFF-4) is more predictive for outcomes in elderly colorectal surgery patients compared to existing models.

• In a study of 27,875 patients over 75, mFF-4 better predicted complications like mortality and prolonged hospital stays, with odds ratios exceeding 2.0 for high frailty groups.
• The model showed higher accuracy (AUC >0.7) and less variability than the modified five-factor index.

This mFF-4 can enhance surgical decision-making and patient selection for better outcomes in frail older adults.