This study aimed to characterize the current patterns of perioperative prophylactic antibiotic use and to systematically evaluate the association between different antibiotic classes and the occurrence of POD, thereby providing clinically relevant safety evidence for perioperative antibiotic decision-making and delirium prevention strategies.

This prospective, observational, single-center cohort analysis was a substudy of the Perioperative Database of Chinese Elderly Patients (PDCEP) study.

Inclusion Criteria:

• patients over 65 years old
• patients undergoing elective non-cardiac surgery

Exclusion Criteria:

• older adult patients who had history of psychotic disorders
• history of neurological disease
• conditions that would make assessments for delirium unreliable
• preoperative infection
• severe hepatic and renal dysfunction, minor and intermediate clean-incision surgery
• missing data exceeding 5%, and no medication records

The study included older adult patients (aged 65 years) scheduled for elective non-cardiac surgery in the First Medicine Department of the Chinese PLA General Hospital between April 2020 and April 2022, from whom complete medication records were obtained.