Association between preoperative anemia and postoperative delirium in elderly patients undergoing non-cardiac surgery: a retrospective observational study.

Abstract

Background: The association between preoperative anemia and postoperative delirium (POD) is unclear. We sought to evaluate the effect of preoperative anemia on the risk of POD in elderly patients after non-cardiac surgery.

Methods: We retrospectively analyzed 62,600 patients aged over 60 years undergoing non-cardiac surgery between January 2011 and June 2019. The patients were divided into two groups according to the presence of preoperative anemia defined as hemoglobin < 13 g/L for men and < 12 g/dl for women. Anemia was further categorized into mild or moderate-to-severe anemia based on a cutoff of 11 g/dl. The primary outcome was POD within 7 d after surgery. The secondary outcomes included one- and three-year mortality after surgery. The inverse probability of treatment weighting (IPTW) method was used to adjust for confounders between the two groups.

Results: The overall incidence of POD was 3.9% (2,447 / 62,600) within 7 d after surgery. After IPTW, preoperative anemia was significantly associated with increased risk of POD (odds ratio [OR], 1.42; 95% CI, 1.30-1.55; P < 0.001). Also, the risk of POD increased with the severity of anemia (OR, 1.32; 95% CI, 1.18-1.47; P < 0.001 for mild anemia; and OR, 1.70; 95% CI, 1.50-1.93; P < 0.001 for moderate-to-severe anemia). This association was similar for one- and three-year mortality.

Conclusions: Preoperative anemia was associated with an increased risk of POD in elderly patients after non-cardiac surgery. Further investigations are required to verify whether preoperative anemia is a modifiable risk factor for POD.