Association between AAR and secondary outcome.

Background
Prior studies have linked the aspartate aminotransferase to alanine aminotransferase ratio (AAR) with negative health outcomes in the elderly and specific populations. However, the impact of AAR on the prognosis of the entire population in the intensive care unit (ICU) remains unclear. This study aimed to determine the correlation between AAR and the mortality among adult ICU patients.
Method
Patient data were retrieved from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database and stratified into quartiles by AAR. Survival analysis using the Kaplan-Meier curves was conducted to compare survival across quartiles. The primary outcome was 28-day mortality, with secondary outcomes including 60-day, 90-day, and 365-day mortality, along with ICU-free, ventilator-free, and vasopressor-free days within the first 28 days. The association between AAR and mortality was evaluated using Cox proportional hazards regression analysis complemented by a restricted cubic spline. Furthermore, the eICU Collaborative Research Database (eICU-CRD) was used as an external validation cohort for sensitivity analysis.
Result
The study included 20,225 patients with a mean age of 63.7 ± 17.5 years. Kaplan-Meier analysis indicated a higher risk of 28-day mortality for patients with higher AAR (log-rank P < 0.001). After adjusting for confounders, the AAR was significantly related to 28-day mortality (HR = 1.04, 95% CI: 1.03–1.06, P < 0.001) and other mortality benchmarks, exhibiting an inverted L-shaped relationship. The inflection point of the AAR for 28-day mortality was 2.60. Below this threshold, each unit increase in the AAR was associated with a 19% rise in the risk of 28-day mortality (HR = 1.19, 95% CI: 1.11–1.27, P < 0.001), with a plateau observed above this threshold. Subgroup and sensitivity analyses further confirmed the robustness and generalizability of the study.
Conclusion
AAR demonstrated a significant association with 28-day, 60-day, 90-day, and 365-day mortality, characterized by an inverted L-shaped pattern.

研究背景
既往研究已将天冬氨酸氨基转移酶与丙氨酸氨基转移酶比值（aspartate aminotransferase to alanine aminotransferase ratio, AAR）与老年人群及特定人群的不良健康结局相关联。然而，AAR对重症监护病房（intensive care unit, ICU）全人群预后的影响尚不明确。本研究旨在明确AAR与成人ICU患者病死率之间的相关性。

研究方法
本研究从重症监护医学信息数据库第四版（Medical Information Mart for Intensive Care IV, MIMIC-IV）中提取患者数据，并按AAR水平分为四分位组。采用卡普兰-迈耶（Kaplan-Meier）曲线进行生存分析，以比较不同四分位组患者的生存情况。本研究的主要结局为28天病死率，次要结局包括60天、90天及365天病死率，以及入组后前28天内的无ICU监护日、无机械通气日和无血管活性药物使用日。采用Cox比例风险回归分析结合限制性立方样条，评估AAR与病死率之间的关联。此外，本研究使用eICU协作研究数据库（eICU Collaborative Research Database, eICU-CRD）作为外部验证队列开展敏感性分析。

研究结果
本研究共纳入20225例患者，平均年龄为63.7±17.5岁。卡普兰-迈耶分析显示，AAR水平较高的患者28天病死率风险更高（对数秩检验P<0.001）。校正混杂因素后，AAR与28天病死率（风险比HR=1.04，95%置信区间CI：1.03~1.06，P<0.001）及其他病死率终点均显著相关，呈现倒L型关联。28天病死率对应的AAR拐点为2.60：当AAR低于该阈值时，AAR每升高1个单位，28天病死率风险升高19%（HR=1.19，95%CI：1.11~1.27，P<0.001）；而当AAR高于该阈值时，病死率风险趋于平稳。亚组分析与敏感性分析进一步证实了本研究结果的稳健性与通用性。

研究结论
AAR与28天、60天、90天及365天病死率均存在显著关联，且该关联呈现倒L型模式。