Impact of Preoperative Functional Capacity on Postoperative Mortality and Morbidity: A Prospective Cohort Study

BACKGROUND: Functional capacity is an important determinant of surgical risk, yet the relationship between self-reported metabolic equivalents of task (MET) levels, treated as a multilevel variable, and postoperative outcomes remains unclear. This study evaluated the association between categorized MET levels and short- and long-term mortality and morbidity. METHODS: This dual-center prospective cohort study enrolled adults undergoing elective noncardiac surgery at Karolinska University Hospital (Solna and Huddinge, Sweden) between 2020 and 2023, excluding obstetric, transplant, day surgery, and nonoperative cases. Preoperative functional capacity was assessed in MET categories (1, 2 to 3, 4 to 5, 6 to 8, 9 or greater). Primary outcomes were all-cause mortality at 30 and 365 days; secondary outcomes were days at home alive (DAH) 30 and DAH365. Analysis used accelerated failure time models and logistic quantile regression. RESULTS: In total, 38,293 patients were included. The incidence of 30- and 365-day mortality was 220 (0.6%) and 2061 (5.4%), respectively. In the 365-day mortality analysis, adjusted accelerated failure time models showed progressively shorter relative median survival times with decreasing MET levels compared to MET 9 or greater: 0.75 (0.56 to 0.98) for MET 6 to 8, 0.52 (0.40 to 0.68) for MET 4 to 5, 0.39 (0.29 to 0.51) for MET 2 to 3, and 0.24 (0.16 to 0.34) for MET 1. The adjusted marginal absolute risk difference in 365-day mortality was distinct across all MET categories: 0.8% (95% CI, 0.1 to 1.5) for MET 6 to 8, 2.3% (1.6 to 2.90) for MET 4 to 5, 3.8% (2.91 to 4.6) for MET 2 to 3, and 7.2% (5.2 to 9.8) for MET 1. Lower MET levels were also associated with fewer days alive and at home at 365 days (DAH365), particularly in the lower quantiles. CONCLUSIONS: Self-reported functional capacity, categorized by MET levels, is associated with both short- and long-term postoperative mortality and morbidity in a dose-response-like manner. These findings support continued use of MET in preoperative assessments and suggest that granular MET categorization enhances risk stratification.