Supplementary Material for: Serum Sodium Levels and Patient Outcomes in an Ambulatory Clinic-Based Chronic Kidney Disease Cohort

Background: Chronic kidney disease (CKD) patients are prone to both hypo- and hypernatremia. Little has been published on the epidemiology of hypo- and hypernatremia in ambulatory patients with non-dialysis CKD. Methods: Data collected in two contemporaneous CKD cohort studies, the Renal Research Institute (RRI)-CKD study (n = 834) and the Study of Treatment of Renal Insufficiency: Data and Evaluation (STRIDE) (n = 1,348) were combined and analyzed to study the association between serum sodium (Na+) and clinical outcomes. Results: Baseline estimated glomerular filtration rate (eGFR) and Na+ were 26 ± 11 ml/min/1.73 m2 and 140.2 ± 3.4 mEq/l, respectively. The prevalence of Na+ ≤135 mEq/l and ≥144 mEq/l was 6 and 16%, respectively. Higher baseline Na+ was significantly associated with male sex, older age, systolic blood pressure, BMI, serum albumin, presence of heart failure, and lower eGFR. The risk of end-stage renal disease (ESRD) was marginally significantly higher among patients with Na+ ≤135 mEq/l, compared with 140< Na+ <144 mEq/l (referent), in time-dependent models (adjusted hazard ratio, HR = 1.52, p = 0.06). Mortality risk was significantly greater at 135< Na+ ≤140 mEq/l (adjusted HR = 1.68, p = 0.02) and Na+ ≥144 mEq/l (adjusted HR = 2.01, p = 0.01). Conclusion: CKD patients with Na+ ≤135 mEq/l were at a higher risk for progression to ESRD, whereas both lower and higher Na+ levels were associated with a higher risk of mortality. While caring for CKD patients, greater attention to serum sodium levels by clinicians is warranted and could potentially help improve patient outcomes.

背景：慢性肾脏病（Chronic kidney disease, CKD）患者易同时发生低钠血症与高钠血症。目前针对非透析慢性肾脏病门诊患者的低钠血症与高钠血症流行病学研究鲜有报道。
方法：本研究合并两项同期开展的慢性肾脏病队列研究数据——肾脏研究研究所（Renal Research Institute, RRI）-CKD研究（n=834）与《肾功能不全治疗研究：数据与评估》（STRIDE，n=1348），分析血清钠（Na+）水平与临床结局的关联。
结果：受试者基线估算肾小球滤过率（eGFR）与血清钠水平分别为26±11 ml/min/1.73m²和140.2±3.4 mEq/L。血清钠≤135 mEq/L与≥144 mEq/L的患病率分别为6%和16%。基线血清钠水平升高与男性性别、高龄、收缩压升高、体质量指数（BMI）升高、血清白蛋白水平、合并心力衰竭及eGFR降低显著相关。在时间依赖性模型中，以140<Na+<144 mEq/L为参照组，血清钠≤135 mEq/L患者的终末期肾病（ESRD）发病风险呈临界显著升高（校正后风险比HR=1.52，P=0.06）。血清钠处于135<Na+≤140 mEq/L（校正HR=1.68，P=0.02）及≥144 mEq/L（校正HR=2.01，P=0.01）区间的患者，死亡风险均显著升高。
结论：血清钠≤135 mEq/L的慢性肾脏病患者进展为终末期肾病的风险更高，而血清钠水平过低或过高均与死亡风险升高相关。临床医师在诊疗慢性肾脏病患者时，应更加关注其血清钠水平，这或有助于改善患者临床结局。