Objective:

To explore the influence of cognitive impairment on postoperative outcomes in older patients undergoing knee arthroplasty, focusing on postoperative delirium, discharge disposition, length of hospital stay, and perioperative blood transfusions.

Approach:

• Study Design: A nationwide retrospective cohort study utilizing anonymized data from the Japanese DPC database, approved by an institutional review board.
• Data Source: Data sourced from Japan’s DPC reimbursement database covering April 2016 to March 2023, involving approximately 1,100 hospitals.
• Inclusion/Exclusion Criteria: Eligible patients underwent primary knee arthroplasty, identified by specific ICD-10 codes. Exclusions included trauma or tumor-related cases.
• Exposure of Interest: Pre-existing cognitive impairment at admission, categorized using ICD-10 diagnostic codes.
• Outcomes of Interest: Primary outcome was postoperative delirium identified through ICD-10 codes.

Key Findings:

• Cognitive impairment is associated with an increased risk of postoperative delirium.
• Patients with cognitive impairment are less likely to be discharged directly to home.
• Cognitive impairment may influence length of hospital stay and incidence of blood transfusions.

Interpretation:

The study highlights the significant impact of cognitive impairment on postoperative outcomes in older patients undergoing knee arthroplasty.

Limitations:

• Retrospective design may introduce biases.
• Data limited to hospitals participating in the DPC system.
• Potential confounding factors may not be fully accounted for.

Conclusion:

Insights from this study can inform perioperative management practices for older adults undergoing knee arthroplasty.