Authors: Valadkhani A et al.
Anesthesiology 144(3):525-534, March 2026.
Impact of Preoperative Functional Capacity on Postoperative Mortality and Morbidity: A Prospective Cohort Study.
This prospective cohort study evaluated whether self-reported functional capacity, measured using metabolic equivalents of task (MET), predicts postoperative mortality and morbidity in patients undergoing elective noncardiac surgery. Functional capacity has long been used in preoperative risk assessments, often simplified into a binary threshold of less than 4 METs versus 4 METs or greater. However, the predictive value of self-reported MET levels and the usefulness of more granular categorization remain subjects of debate.
The investigators conducted a dual-center study at Karolinska University Hospital in Sweden between 2020 and 2023. Adult patients undergoing elective noncardiac surgery were included, while obstetric, transplant, day surgery, and nonoperative cases were excluded. Preoperative functional capacity was assessed through patient-reported MET levels and categorized into five groups:
• 1 MET
• 2–3 METs
• 4–5 METs
• 6–8 METs
• 9 METs or greater
The primary outcomes were all-cause mortality at 30 days and 365 days after surgery. Secondary outcomes included “days alive and at home” (DAH), a composite outcome reflecting both survival and hospital utilization, measured at both 30 and 365 days.
A total of 38,293 patients were included in the analysis. The overall mortality rate was 0.6% at 30 days and 5.4% at 365 days.
The results demonstrated a clear dose–response relationship between decreasing functional capacity and worse postoperative outcomes. Compared with patients with the highest functional capacity (9 METs or greater), progressively lower MET levels were associated with shorter survival times at one year.
Adjusted models showed relative reductions in median survival time as functional capacity declined:
• MET 6–8: survival time ratio 0.75
• MET 4–5: survival time ratio 0.52
• MET 2–3: survival time ratio 0.39
• MET 1: survival time ratio 0.24
Absolute risk differences in 365-day mortality also increased steadily with lower MET categories:
• MET 6–8: +0.8% mortality risk
• MET 4–5: +2.3%
• MET 2–3: +3.8%
• MET 1: +7.2%
Lower functional capacity was also associated with worse recovery outcomes. Patients in lower MET categories spent fewer days alive and at home during the first year following surgery, indicating both higher mortality and greater postoperative healthcare utilization.
Importantly, these findings suggest that functional capacity is not simply a binary risk marker but instead demonstrates a graded relationship with postoperative outcomes. More detailed categorization of MET levels appears to provide better risk stratification than the traditional threshold approach.
The study supports continued use of self-reported MET levels during preoperative evaluation while emphasizing the value of using multiple MET categories rather than a simple cutoff. Incorporating more granular functional capacity assessments may help clinicians more accurately estimate perioperative risk and guide preoperative optimization strategies.
Key Points
• Functional capacity measured in METs is widely used in preoperative assessment.
• This study analyzed 38,293 patients undergoing elective noncardiac surgery.
• Lower MET levels were associated with progressively higher postoperative mortality.
• One-year mortality increased from patients with ≥9 METs to those with lower categories in a dose–response pattern.
• Lower MET levels were also associated with fewer days alive and at home after surgery.
• Using multiple MET categories may improve perioperative risk stratification compared with the traditional <4 MET threshold.
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