Bidirectional Relationship Between Hypoalbuminemia and Postoperative Pneumonia in Elderly Hip Fracture Patients: A Retrospective Cohort Study

Postoperative pneumonia is a common and severe complication following hip fracture (HF) surgery in the elderly. Hypoalbuminemia, a marker of poor nutritional status and systemic inflammation, is widely recognized as a predictor of adverse outcomes. However, their bidirectional relationship in elderly HF patients remains underexplored. This retrospective cohort study was conducted in China enrolling elderly patients (≥65 years) with HFs between Mar 2020 and Feb 2023. After predefined participants selection inclusion and exclusion criteria, 1661 surgically treated HF patients were included and analyzed utilizing multiple statistical models, including univariate logistic regression, Lasso regression, and Boruta algorithm for variable selection, while multivariate logistic regression and propensity score matching (PSM) for assess the bidirectional relationship between hypoalbuminemia and postoperative pneumonia. All participants' demographics, injury-related data, surgery-related data, perioperative complications, and two-year follow-up mortality rates were collected and compared. A total of 1,661 patients were included, of whom 144 developed postoperative pneumonia (8.67%). Preoperative hypoalbuminemia was identified as an independent risk factor for postoperative pneumonia (OR: 7.96, 95% CI: 4.08-15.53, P<0.001), while postoperative pneumonia itself was associated with an increased risk of developing hypoalbuminemia (OR: 2.34, 95% CI: 1.62-3.38, P<0.001). PSM, as sensitivity analyses, further confirmed that postoperative pneumonia itself exacerbates hypoalbuminemia, creating a detrimental cycle. In addition, postoperative pneumonia significantly prolonged hospital stays, increased complication, and elevated mortality rates at 3 months to 2 years (OR: 1.83-3.43, all P<0.05) follow-up period. Preoperative hypoalbuminemia is a significant predictor of postoperative pneumonia in elderly patients with HFs, and postoperative pneumonia, in turn, exacerbates hypoalbuminemia, creating a deleterious cycle. Early nutritional assessment and intervention are essential in breaking this cycle and improving outcomes. These findings support the incorporation of routine nutritional screening and optimization into the preoperative care of elderly HF patients to reduce complications and enhance recovery.