Association of hemoglobin levels at admission with postoperative pneumonia in elderly patients with hip fracture: A retrospective cohort study

Previous studies have suggested a correlation between low preoperative hemoglobin (Hb) levels and postoperative pneumonia (POP) in elderly patients with hip fractures. However, the exact inflection point of Hb level that increases the risk of POP remains unclear. This study aimed to investigate the quantitative relationship between preoperative Hb levels and the incidence of POP in this patient population. This retrospective study included 1417 elderly patients with hip fractures who were admitted to the Department of Orthopedics at Shenzhen Second People's Hospital between January 2012 and December 2021. Demographic and clinical data, including laboratory test results, were analyzed and compared to explore the relationship between Hb levels at admission and the incidence of POP in this patient population. This study included 1417 elderly patients with hip fractures, comprising 382 males and 1035 females, with a mean age of 77.57 ± 8.73 years. The incidence of POP was 6.21% (88/1417) in this patient population. After adjusting for confounding factors in model II, the regression equation showed that the incidence of POP decreased by 2% with each 1 g/L increment in Hb levels (OR: 0.98, 95% CI: 0.97-1.00; P = .0211). Additionally, a two-piecewise regression model was used to explore the relationship between Hb levels and POP incidence, after adjusting for confounding factors. Threshold effect analysis showed that the inflection point was 83.5 g/L. On the left side of the inflection point, Hb levels were negatively correlated with the incidence of POP (OR: 0.91, 95% CI: 0.86-0.97, P = .0030). There was a nonlinear relationship between preoperative Hb level and POP in elderly patients with hip fractures. When Hb levels were lower than 83.5 g/L, preoperative Hb levels were negatively correlated with POP.