摘要目的:探究计算机体层成像图像中L1腰椎横突水平的肌肉脂肪浸润指数（intramuscular adipose tissue index，IATI）与维持性透析患者全因死亡风险的相关关系，以期为改善透析患者预后提供参考依据。方法:该研究为多中心回顾性队列研究。回顾性收集2017年1月1日至2019年12月31日东南大学附属中大医院、南京医科大学附属泰州人民医院、扬州大学附属医院、苏州大学附属第三医院4家三甲医院的维持性血液透析或腹膜透析患者的临床资料。IATI为低衰减值肌肉（low attenuation muscle，LAM）密度/骨骼肌密度比值。采用受试者工作特征曲线确定IATI的最佳切点值，并作为临界值将患者分为高IATI组和低IATI组，比较2组基线临床资料和L1椎体层面测量参数的差异。随访截至2022年12月23日，随访终点事件定义为患者3年内发生全因死亡。采用Kaplan-Meier生存曲线和Log-rank检验分析2组患者生存率及其差异。多因素Cox回归分析法分析IATI与维持性透析患者全因死亡的相关性。多因素Logistic回归分析法分析高IATI的影响因素。结果:该研究纳入维持性透析患者478例，年龄（53.55±13.19）岁，男319例（66.7%），血液透析365例（76.4%），腹膜透析113例（23.6%）。低IATI（<0.42）组376例（78.7%），高IATI（≥0.42）组102例（21.3%）。高IATI组患者年龄≥60岁比例（ χ2=24.746， P<0.001）、糖尿病比例（ χ2=5.570， P=0.018）、空腹血糖（ t=-2.145， P=0.032）、LAM密度（ t=-3.735， P<0.001）、LAM指数（ t=-7.072， P<0.001）及LAM面积/骨骼肌面积比值（ Z=-9.630， P<0.001）均高于低IATI组，而男性比例（ χ2=11.116， P=0.001）、血清白蛋白（ Z=2.708， P=0.007）和骨骼肌密度（ t=12.380， P<0.001）均低于低IATI组。Kaplan-Meier生存分析结果显示，低IATI组3年生存率显著高于高IATI组（Log-rank χ2=19.188， P<0.001）。多因素Cox回归分析结果显示，IATI<0.42［<0.42/≥0.42， HR（95% CI）：0.50（0.31～0.83）， P=0.007］为维持性透析患者全因死亡的独立保护因素，年龄≥60岁［ HR（95% CI）：2.61（1.60～4.23）， P<0.001］、糖尿病［ HR（95% CI）：1.71（1.06～2.78）， P=0.029］和高中性粒细胞/淋巴细胞比值［ HR（95% CI）：1.04（1.00～1.07）， P=0.049］均为维持性透析患者全因死亡的独立危险因素。经逐步Cox回归分析校正，IATI<0.42仍是维持性透析患者全因死亡的独立保护因素［<0.42/≥0.42， HR（95% CI）：0.45（0.27～0.76）， P=0.003］。多因素Logistic回归分析结果显示，低骨骼肌密度［ OR（95% CI）：0.84（0.81～0.88）， P<0.001］和高三酰甘油［ OR（95% CI）：1.39（1.07～1.82）， P=0.015］均为IATI≥0.42的独立影响因素。 结论:L1腰椎横突水平IATI<0.42是维持性透析患者全因死亡的保护因素。高质量骨骼肌局限性肌肉脂肪变性可能降低维持性透析患者全因死亡的风险。

abstractsObjective:To investigate the relationship between intramuscular adipose tissue index (IATI) calculated from computed tomography images at transverse process of the first lumbar and all-cause mortality in maintenance dialysis patients, and to provide a reference for improving the prognosis in these patients.Methods:It was a multicenter retrospective cohort study. The clinical data of patients who received maintenance hemodialysis or peritoneal dialysis treatment from January 1, 2017 to December 31, 2019 in 4 grade Ⅲ hospitals including Zhongda Hospital Affiliated to Southeast University, Taizhou People's Hospital Affiliated to Nanjing Medical University, Affiliated Hospital of Yangzhou University, and the Third Affiliated Hospital of Soochow University were retrospectively collected. IATI was calculated by low attenuation muscle (LAM) density/skeletal muscle density. The receiver-operating characteristic curve was used to determine the optimal cut-off value of IATI, and the patients were divided into high IATI group and low IATI group according to the optimal cut-off value. The differences of baseline clinical data and measurement parameters of the first lumbar level between the two groups were compared. The follow-up ended on December 23, 2022. The endpoint event was defined as all-cause mortality within 3 years. Kaplan-Meier survival curve and log-rank test were used to analyze the survival rates and the differences between the two groups. Multivariate Cox regression analysis models were used to analyze the association between IATI and the risk of all-cause mortality in maintenance dialysis patients. Multivariate logistic regression analysis model was used to analyze the influencing factors of high IATI.Results:A total of 478 patients were eligibly recruited in this study, with age of (53.55±13.19) years old and 319 (66.7%) males, including 365 (76.4%) hemodialysis patients and 113 (23.6%) peritoneal dialysis patients. There were 376 (78.7%) patients in low IATI (<0.42) group and 102 (21.3%) patients in high IATI (≥0.42) group. The proportion of age ≥ 60 years old ( χ2=24.746, P<0.001), proportion of diabetes mellitus ( χ2=5.570, P=0.018), fasting blood glucose ( t=-2.145, P=0.032), LAM density ( t=-3.735, P<0.001), LAM index ( t=-7.072, P<0.001), and LAM area/skeletal muscle area ratio ( Z=-9.630, P<0.001) in high IATI group were all higher than those in low IATI group, while proportion of males ( χ2=11.116, P<0.001), serum albumin ( Z=2.708, P=0.007) and skeletal muscle density ( t=12.380, P<0.001) were lower than those in low IATI group. Kaplan-Meier survival analysis showed that the 3-years overall survival rate of low IATI group was significantly higher than that in high IATI group (Log-rank χ2=19.188, P<0.001). Multivariate Cox regression analysis showed that IATI<0.42 [<0.42/≥0.42, HR(95% CI): 0.50 (0.31-0.83), P=0.007] was an independent protective factor of all-cause mortality, and age ≥60 years old [ HR (95% CI): 2.61 (1.60-4.23), P<0.001], diabetes mellitus [ HR (95% CI): 1.71 (1.06-2.78), P=0.029] and high blood neutrophil/lymphocyte ratio [ HR (95% CI): 1.04 (1.00-1.07), P=0.049] were the independent risk factors of all-cause mortality in maintenance dialysis patients. Stepwise Cox regression analysis showed that IATI<0.42 was still an independent protective factor of all-cause mortality in maintenance dialysis patients [<0.42/≥0.42, HR (95% CI): 0.45 (0.27-0.76), P=0.003]. Multivariate logistic regression analysis showed that low skeletal muscle density [ OR (95% CI): 0.84 (0.81-0.88), P<0.001] and high serum triglyceride [ OR (95% CI): 1.39 (1.07-1.82), P=0.015] were the independent influencing factors of IATI≥0.42. Conclusion:IATI<0.42 of the first lumbar level is an independent protective factor of all-cause mortality in maintenance dialysis patients. Localized myosteatosis within high-quality skeletal muscle may reduce the risk of all-cause mortality in these patients.