Sex differences in surgical patients with preoperative iron deficiency anemia

BACKGROUND: Preoperative iron deficiency anemia (IDA) affects 30%-44% of non-cardiac surgical patients and is associated with poor postoperative outcomes. Few studies have examined IDA surgical patients' outcomes by sex. STUDY DESIGN AND METHODS: TriNetX Research Network was queried from 2005 to 2025. We compared adult female and male surgical patients with IDA within 1 month preoperatively. Sub-analyses were performed for ages 18-55, 56+ years, and cardiac surgical patients. We performed propensity score matching on surgical type, demographics, and comorbidities. We tracked 30-day postoperative mortality, respiratory, renal, ischemic, thrombotic, infectious, and combined morbidity, RBC transfusions, and hemorrhage. RESULTS: After matching, 418,172 IDA patients were in each cohort. Female patients had lower risk of 30-day postoperative mortality than male patients (1.79% vs. 2.35%, Risk Ratio (RR): 0.76 [95% Confidence Interval: 0.74-0.79]), respiratory morbidity (1.25% vs. 2.16%, RR: 0.58 [0.56-0.60]), renal morbidity (6.00% vs. 8.67%, RR: 0.69 [0.68-0.70]), ischemic morbidity (3.04% vs. 3.89%, RR: 0.78 [0.76-0.80]), thromboembolic morbidity (2.86% vs. 3.39%, RR: 0.84 [0.82-0.86]), infectious morbidity (5.17% vs. 7.96%, RR: 0.65 [0.64-0.66]), and hemorrhage (0.18% vs. 0.24%, RR: 0.77 [0.70-0.85]). Sex had a lesser impact after cardiac surgery. Female sex was associated with a lower risk of infectious morbidity, combined morbidity, and renal morbidity; all other outcomes were not significant. DISCUSSION: Our findings underscore the importance of incorporating sex-specific considerations into perioperative risk stratification, particularly in patients with preoperative anemia. Most sex differences were not present in cardiac surgery patients, suggesting potential interactions between surgical type, baseline risk, and transfusion or anticoagulation practices.