Preoperative hemoglobin glycation index and postoperative complications after non-cardiac surgery: a retrospective cohort study

Abstract Purpose Perioperative metabolic vulnerability is an important contributor to postoperative morbidity, yet preoperative risk stratification relies largely on conventional glycemic measures such as hemoglobin A1c (HbA1c) and fasting plasma glucose (FPG). Hemoglobin glycation index (HGI) quantifies interindividual discordance between HbA1c and contemporaneous glycemia and may capture metabolic phenotypes not reflected by absolute glucose values. We investigated the association between preoperative HGI and postoperative outcomes in adults undergoing non-cardiac surgery. Methods We conducted a retrospective single-center cohort study including adult inpatients who underwent non-cardiac surgery under general anesthesia between January 2013 and June 2024. Patients with both preoperative HbA1c and FPG measured within 60 days before surgery were included. HGI was calculated as the residual of observed HbA1c minus HbA1c predicted from FPG using a cohort-specific linear regression model. The primary outcome was any postoperative complication occurring before hospital discharge. Secondary outcomes included major complications (Clavien–Dindo grade ≥ III), organ-specific complications, deep-vein thrombosis, Intensive Care Unit (ICU) admission, hospital and postoperative length of stay, and in-hospital mortality. Associations were evaluated using multivariable regression models with HGI analyzed as a continuous variable (per 1–SD increase) and by quartiles (Q2 as reference), complemented by restricted cubic spline analyses and prespecified subgroup analyses. Results A total of 24,307 patients were included (mean age 58.8 ± 13.3 years; 51% women). Postoperative complications occurred in 8.4% of patients. In adjusted continuous models, higher HGI was independently associated with postoperative complications (odds ratio OR per 1–SD increase 1.068; 95% confidence interval CI, 1.018–1.120; P = 0.007), urinary complications (OR 1.155; 95% CI, 1.024–1.301; P = 0.018), and longer total hospital length of stay (adjusted mean ratio 1.030; 95% CI, 1.017–1.043; P = 0.001). Quartile analyses demonstrated the lowest risk of postoperative complications in the mid-range HGI group, with higher risks observed at extreme HGI values. Restricted cubic spline models revealed an approximately linear association between HGI and overall postoperative complications, while outcome-specific nonlinear relationships were observed for major complications, ICU admission, and in-hospital mortality. Associations were generally consistent across subgroups, with no statistically significant interaction detected across prespecified strata. Conclusions Preoperative hemoglobin glycation index was independently associated with postoperative complications after non-cardiac surgery and identified nonlinear risk patterns for selected severe outcomes. HGI may serve as a complementary perioperative metabolic risk marker beyond HbA1c and fasting plasma glucose to provide incremental risk information.