The Relationship between the Blood Urea Nitrogen/Creatinine Ratio and Prognosis in Intensive Care Unit Survivors—A Retrospective Study Based on the MIMIC-IV Database

背景：重症监护病房(ICU)幸存者死亡风险升高已成为临床研究的一个重要焦点。尿素与肌酐比值(UCR)是评估危重患者分解代谢状态的潜在生物标志物，与各种病理条件下的不良结果有关。然而，UCR水平与ICU幸存者预后之间的关系仍未得到充分的了解。方法：基于MIMIC-IV数据库开展回顾性队列分析，纳入ICU住院时间超过48小时且存活至转出医院的患者。主要结局为出院后30天及1年全因死亡率。采用单因素及多因素Cox回归模型分析UCR与ICU幸存者死亡风险关系的独立性。通过限制性立方样条(RCS)检验非线性趋势并计算拐点，最后进行亚组分析检验UCR水平在不同患者人群中预后价值的稳健性。结果：共有16,613例患者入组研究，30天和1年全因死亡率分别为7.5%和20.8%。ICU幸存者UCR水平与患者30天全因死亡率之间存在显著的线性正相关，UCR越高，30天死亡风险越高；而UCR水平与患者1年全因死亡率之间呈J型关系，阈值效应分析表明拐点为UCR = 11，在拐点左侧，UCR越高，1年死亡风险越低(HR [95% CI], 0.956 [0.918~0.995], p = 0.027)，拐点右侧则相反(HR 95% CI, 1.023 [1.02~1.026], p Background: The elevated mortality risk among survivors of the intensive care unit (ICU) has emerged as a significant focus of clinical investigation. The urea-to-creatinine ratio (UCR) serves as a potential biomarker for evaluating the catabolic state of critically ill patients and has been linked to adverse outcomes across various pathological conditions. Nevertheless, the association between UCR levels and the prognostic outcomes of ICU survivors remains inadequately understood. Method: Patients who were admitted to the intensive care unit (ICU) for more than 48 hours and survived to discharge were retrospectively collected from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database. The primary outcomes evaluated were all-cause mortality at 30 days and 1 year. The association between the UCR and these outcomes was examined using multivariate Cox proportional hazards regression models. To explore potential non-linear relationships, restricted cubic spline (RCS) curves were plotted based on the adjusted models. Subgroup analyses were conducted to assess the heterogeneity of this association across different patient populations. Results: A total of 16,613 patients were enrolled in the study, with 30-day and 1-year all-cause mortality rates of 7.5% and 20.8%, respectively. After adjusting for confounders, there was a significant positive linear relationship between UCR levels and patients’ 30-day mortality (HR [95% CI], 1.031 [1.027~1.036], p p = 0.027), and the opposite was true on the right side of the inflection point (HR 95% CI, 1.023 [1.02~1.026], p < 0.001). The results of the subgroup analyses suggest a similar relationship in different populations. Conclusion: Among intensive care unit survivors, a significant positive linear association was observed between UCR levels and 30-day all-cause mortality, while a J-shaped relationship was identified for 1-year all-cause mortality. Elevated UCR levels may serve as a valuable indicator for identifying patients at an increased risk of mortality, thereby informing discharge planning and enabling the implementation of targeted therapeutic interventions.