Preoperative Lymphocyte-to-Monocyte Ratio and Postoperative Delirium by Frailty Status in Older Surgical Patients

Association Between Preoperative Lymphocyte-to-Monocyte Ratio and Postoperative Delirium According to Frailty Status in Older Surgical Patients: A Prospective Cohort Study

Both frailty and a reduced preoperative lymphocyte-to-monocyte ratio (LMR) are known risk factors for postoperative delirium (POD). However, whether the relationship between LMR and POD varies by frailty status remains unclear. This study aimed to evaluate the frailty-stratified association between preoperative LMR and POD in older surgical patients.

Study Overview

• Status: Completed
• Conditions: Postoperative Delirium (POD); Lymphocyte; Frailty at Older Adults

• Study Type: Observational
• Enrollment (Actual): 6475

Contacts and Locations

Study Locations

• China
  • Beijing, China
    • 28 Fuxing Road, Haidian District

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Patients were grouped according to the preoperative lymphocyte-to-monocyte ratio (LMR) and were further stratified into subgroups based on frailty status, which was assessed one day before surgery using the FRAIL scale. Postoperative delirium was assessed using the 3-Minute Diagnostic Interview for Confusion Assessment Method (3D-CAM) for seven consecutive postoperative days or until hospital discharge, whichever occurred first.

Description

Inclusion Criteria:

• Aged ≥65 years;
• Underwent elective noncardiac, nonneurosurgical procedures;
• Completed the preoperative health and functional status questionnaire.

Exclusion Criteria:

• Severe dementia, language disorders, significant hearing or visual impairments, or coma;
• Cognitive function below the Mini-Mental State Examination thresholds (<18 for illiterate individuals, <21 for individuals with primary education, and <25 for individuals with secondary education or higher);
• Surgery performed under local anesthesia or monitored anesthesia care;
• Missing lymphocyte or monocyte count data;
• Missing postoperative delirium assessment;
• Incomplete preoperative FRAIL scale evaluation;
• Missing data for more than 20% of covariates.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

A retrospective cohort study based on prospectively collected data.; Patients were grouped according to the preoperative lymphocyte-to-monocyte ratio (LMR), calculated as the lymphocyte count divided by the monocyte count. Lymphocyte and monocyte values were obtained from the most recent preoperative laboratory test. Frailty was assessed one day before surgery using the FRAIL scale, which comprises five domains: fatigue, resistance, ambulation, illnesses, and weight loss. Each item is scored as 0 or 1, yielding a total score ranging from 0 to 5, with higher scores indicating greater frailty. Based on the total score, patients were categorized as robust (0 points), pre-frail (1-2 points), or frail (3-5 points).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The primary outcome was the occurrence of postoperative delirium (POD).	The primary outcome was the occurrence of POD, evaluated by trained researchers using the 3-Minute Diagnostic Interview for Confusion Assessment Method (3D-CAM).	POD assessment was performed twice daily for up to seven consecutive postoperative days or until hospital discharge, whichever occurred first.

Collaborators and Investigators

• Sponsor: Chinese PLA General Hospital

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2020
• Primary Completion (Actual): April 30, 2022
• Study Completion (Actual): December 30, 2023

Study Registration Dates

• First Submitted: December 23, 2025
• First Submitted That Met QC Criteria: December 23, 2025
• First Posted (Estimated): January 7, 2026

Study Record Updates

• Last Update Posted (Actual): January 9, 2026
• Last Update Submitted That Met QC Criteria: January 8, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: frailty; postoperative delirium; older surgical patients; lymphocyte-to-monocyte ratio
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Mental Disorders; Postoperative Complications; Pathologic Processes; Confusion; Neurobehavioral Manifestations; Neurocognitive Disorders; Delirium; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Frailty; Emergence Delirium
• Other Study ID Numbers: LMR - POD

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No