U shaped association between fibrinogen and one year mortality in women undergoing coronary artery bypass grafting

Fibrinogen serves as a vital hemostatic factor and an early marker of inflammation, with established associations to unfavorable clinical outcomes, particularly in cardiovascular contexts. However, its specific effects in female populations are not well understood. This research aims to evaluate the relationship between serum fibrinogen concentrations and long-term mortality among female patients undergoing coronary artery bypass grafting (CABG). We analyzed data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. The primary outcome assessed was one-year mortality, while secondary outcomes included hospital length of stay and incidence of sepsis. The associations between fibrinogen concentrations and clinical outcomes were evaluated retrospectively utilizing Cox proportional hazards models, along with subgroup analyses and restricted cubic splines (RCS). A total of 1,097 patients were included, with an average age of 70.8 years (range: 60.8–80.8) and a mean body mass index (BMI) of 31 kg/m² (range: 24–38). Analysis using Cox regression revealed a significantly elevated risk of one-year mortality linked to both low and high fibrinogen levels (Q1: Hazard ratio (HR) 2.91, 95%ConfidenceInterval (95% CI) 1.14 ~ 7.46; Q6: HR 4.3, 95% CI 1.66 ~ 11.13). Additionally, RCS analysis illustrated a U-shaped relationship between fibrinogen levels and mortality, identifying an inflection point at 174 mg/dL. These findings were corroborated by stratified and sensitivity analyses. In female patients undergoing CABG, both low and high fibrinogen levels are associated with an elevated risk of one year, mortality, exhibiting a U-shaped relationship. Further prospective research is warranted to validate the associations identified in this study.