Supplementary Material for: Age Difference in the Association between Hyponatremia and Infection-Related Mortality in Peritoneal Dialysis Patients

Objectives: This study aimed to examine the association of serum sodium with infection-related mortality and its age difference among continuous ambulatory peritoneal dialysis (CAPD) patients. Methods: A total of 1,656 CAPD patients from January 2006 to December 2013 were included in this study. All patients were followed up until December 2018. Hyponatremia was defined as serum sodium <135 mmol/L. Cox proportional hazards regression model was used to investigate the relationship between baseline serum sodium levels and infection-related mortality. Results: Participants were aged 47.5 ± 15.3 years, 666 (40.2%) patients were female. Glomerulonephritis was the main cause of end-stage renal disease (61.1%). After a median of 46 months of follow-up, 507 patients died. Among the deaths, 252 (49.7%) died from cardiovascular diseases, 105 (20.7%) from infections, and 150 (29.6%) from other causes. The overall infection-related mortality was 14.8 events per 1,000 patients-year, which was higher in patients aged ≥50 years than those younger than 50 years (28.3 vs. 5.3 events per 1,000 patients-year). In the entire cohort, hyponatremia at was not associated with infection-related (hazards ratios [HR] 1.66, 95% CI 0.91–3.02) and all-cause mortality (HR 1.14, 95% CI 0.83–1.57) after adjusting for potential confounders. There was a significant interaction by age of association of serum sodium with infection-related (p = 0.002) and all-cause (p = 0.0002) death. Age-stratified analysis showed that compared with control group, hyponatremia was independently related to increased risks of infection-related death, but not all-cause mortality in patients aged ≥50 years, with HR of 2.32 (95% CI 1.25–4.32) and 1.33 (95% CI 0.95–1.87), respectively. Conclusions: Hyponatremia was associated with increased risk of infection-related mortality in CAPD patients aged ≥50 years.研究目的：本研究旨在探讨持续性不卧床腹膜透析（continuous ambulatory peritoneal dialysis, CAPD）患者的血清钠水平与感染相关死亡的关联及其年龄差异。 研究方法：本研究纳入2006年1月至2013年12月的1656例CAPD患者，所有患者随访至2018年12月。低钠血症（hyponatremia）定义为血清钠水平低于135 mmol/L。采用Cox比例风险回归模型分析基线血清钠水平与感染相关死亡的关联。 研究结果：研究对象的平均年龄为47.5±15.3岁，其中女性666例，占比40.2%。肾小球肾炎是终末期肾病（end-stage renal disease）的主要病因，占比61.1%。中位随访46个月后，共计507例患者死亡。死亡病例中，252例（49.7%）死于心血管疾病，105例（20.7%）死于感染，150例（29.6%）死于其他原因。总体感染相关死亡率为14.8例/1000患者-年，≥50岁患者的感染相关死亡率（28.3例/1000患者-年）高于50岁以下患者（5.3例/1000患者-年）。在整个研究队列中，校正潜在混杂因素后，低钠血症与感染相关死亡（风险比[HR]=1.66，95%置信区间[CI]：0.91~3.02）及全因死亡（HR=1.14，95%CI：0.83~1.57）均无显著关联。血清钠水平与感染相关死亡（p=0.002）及全因死亡（p=0.0002）的关联存在显著的年龄交互作用。年龄分层分析显示，在≥50岁的CAPD患者中，与对照组相比，低钠血症可独立增加感染相关死亡风险（HR=2.32，95%CI：1.25~4.32），但与全因死亡无显著关联（HR=1.33，95%CI：0.95~1.87）。 研究结论：在≥50岁的CAPD患者中，低钠血症与感染相关死亡风险升高显著相关。