Association Between Postoperative Day 7 Hypoalbuminemia and Mortality After Surgery: A Single-Center Retrospective Landmark Cohort Study

Background/Objectives: We evaluated postoperative day 7 serum albumin for its association with mortality after surgery and whether it varied by frailty or surgical urgency.

Methods

This single-center landmark cohort study was conducted at an 817-bed tertiary hospital (April 2018–March 2025). Follow-up began on day 7 to reduce immortal-time bias. Of 41,506 surgical episodes, 18,296 met the landmark and 14,992 (82%) had day 7 albumin measured. Hypoalbuminemia was <3.0 g/dL. We assessed 365-day mortality by landmark Cox regression. We compared discrimination with the preoperative Surgical Outcome Risk Tool (SORT) and American Society of Anesthesiologists (ASA) physical status, added day 7 albumin to each, and tested effect modification by frailty and urgency.