U-Shaped Association Between Preoperative Fasting Blood Glucose and Postoperative Delirium in Elderly Diabetic Patients: A Multicentre Retrospective Cohort Study
- 1the First Medical Center of Chinese PLA General Hospital
Abstract
ObjectiveThe heightened susceptibility of the aging brain to dysglycemia establishes blood glucose as a pivotal risk factor for postoperative delirium (POD) in elderly diabetic patients. This study investigated the association between preoperative fasting blood glucose (FBG) and POD risk in this population to define the optimal FBG range for POD.
MethodsThis study included 2,157 elderly diabetic patients undergoing non-cardiac surgery between April 2020 and April 2022 in 20 hospitals across China. The POD incidence was prospectively assessed using the 3-minute Diagnostic Interview for Confusion Assessment Method (3D-CAM) within 7 postoperative days. The FBG-POD relationship was retrospectively analysed using restricted cubic splines within Cox proportional hazards model. Thresholds were validated with the machine learning-guided optimal cut-point analysis. A multivariable linear regression model was plotted to compare the distribution of time to POD onset and subgroup analyses were performed based on specific populations.
ResultsA significant U-shaped relationship was observed between preoperative FBG and POD risk (P for nonlinearity=0.03). The hazard ratio identified the risk nadir of FBG at 8.43 mmol L-1. Optimal cut-point analysis defined three risk strata: a hypoglycemic-risk group (FBG [≤]5.92 mmol L-1; 13.3% POD), an optimal-glycemic group (FBG 5.92-9.75 mmol L-1; 9.7% POD), and a hyperglycemic-risk group (FBG >9.75 mmol L-1; 18.5% POD). Compared with the optimal-glycemic group, both the hypoglycemic-risk group (HR=1.65, P<0.001) and the hyperglycemic-risk group (HR=1.51, P=0.03) showed significantly increased risk.
InterpretationPreoperative FBG has a U-shaped association with POD risk in elderly diabetic patients with an optimal lowest-risk range as 5.92-9.75 mmol L-1.
Summary BoxO_ST_ABSWhat is already known on this topicC_ST_ABSO_LIThe aging brain is highly sensitive to dysglycemia, making elderly diabetic patients vulnerable to postoperative delirium. C_LIO_LICurrent perioperative glucose management guidelines lack specific preoperative glycemic targets for preventing delirium in this population. C_LI
What this study addsO_LIPreoperative fasting blood glucose (FBG) has a U-shaped association with postoperative delirium risk in elderly diabetic patients. C_LIO_LIAn optimal neuroprotective FBG range of 5.92-9.75 mmol/L is associated with the lowest risk of delirium. C_LIO_LIBoth hypoglycemia ([≤]5.92 mmol/L) and hyperglycemia (>9.75 mmol/L) independently increase delirium hazard by 65% and 51%, respectively. C_LI
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BibTeX
@misc{zhang2026ushaped,
title = {{U-Shaped Association Between Preoperative Fasting Blood Glucose and Postoperative Delirium in Elderly Diabetic Patients: A Multicentre Retrospective Cohort Study}},
author = {X. Zhang and Y. Zhang and M. Yuan and B. Xu and J. Cao and Y. Liu and J. Lou and W. Shi and Q. Fu and W. Mi},
howpublished = {medRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.20.26366023},
url = {https://www.medrxiv.org/content/10.64898/2026.10.20.26366023v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - U-Shaped Association Between Preoperative Fasting Blood Glucose and Postoperative Delirium in Elderly Diabetic Patients: A Multicentre Retrospective Cohort Study
AU - X. Zhang
AU - Y. Zhang
AU - M. Yuan
AU - B. Xu
AU - J. Cao
AU - Y. Liu
AU - J. Lou
AU - W. Shi
AU - Q. Fu
AU - W. Mi
PY - 2026
DA - 2026/10/20
PB - medRxiv
DO - 10.64898/2026.10.20.26366023
UR - https://www.medrxiv.org/content/10.64898/2026.10.20.26366023v1
AB - ObjectiveThe heightened susceptibility of the aging brain to dysglycemia establishes blood glucose as a pivotal risk factor for postoperative delirium (POD) in elderly diabetic patients. This study investigated the association between preoperative fasting blood glucose (FBG) and POD risk in this population to define the optimal FBG range for POD. MethodsThis study included 2,157 elderly diabetic patients undergoing non-cardiac surgery between April 2020 and April 2022 in 20 hospitals across China. The POD incidence was prospectively assessed using the 3-minute Diagnostic Interview for Confusion Assessment Method (3D-CAM) within 7 postoperative days. The FBG-POD relationship was retrospectively analysed using restricted cubic splines within Cox proportional hazards model. Thresholds were validated with the machine learning-guided optimal cut-point analysis. A multivariable linear regression model was plotted to compare the distribution of time to POD onset and subgroup analyses were performed based on specific populations. ResultsA significant U-shaped relationship was observed between preoperative FBG and POD risk (P for nonlinearity=0.03). The hazard ratio identified the risk nadir of FBG at 8.43 mmol L-1. Optimal cut-point analysis defined three risk strata: a hypoglycemic-risk group (FBG [≤]5.92 mmol L-1; 13.3% POD), an optimal-glycemic group (FBG 5.92-9.75 mmol L-1; 9.7% POD), and a hyperglycemic-risk group (FBG >9.75 mmol L-1; 18.5% POD). Compared with the optimal-glycemic group, both the hypoglycemic-risk group (HR=1.65, P<0.001) and the hyperglycemic-risk group (HR=1.51, P=0.03) showed significantly increased risk. InterpretationPreoperative FBG has a U-shaped association with POD risk in elderly diabetic patients with an optimal lowest-risk range as 5.92-9.75 mmol L-1. Summary BoxO_ST_ABSWhat is already known on this topicC_ST_ABSO_LIThe aging brain is highly sensitive to dysglycemia, making elderly diabetic patients vulnerable to postoperative delirium. C_LIO_LICurrent perioperative glucose management guidelines lack specific preoperative glycemic targets for preventing delirium in this population. C_LI What this study addsO_LIPreoperative fasting blood glucose (FBG) has a U-shaped association with postoperative delirium risk in elderly diabetic patients. C_LIO_LIAn optimal neuroprotective FBG range of 5.92-9.75 mmol/L is associated with the lowest risk of delirium. C_LIO_LIBoth hypoglycemia ([≤]5.92 mmol/L) and hyperglycemia (>9.75 mmol/L) independently increase delirium hazard by 65% and 51%, respectively. C_LI
ER -