Supplementary Material for: Blood Pressure Variability in Older Patients with Chronic Kidney Disease

Introduction: An increased blood pressure variability (BPV) is associated with a high risk of cardiovascular events in the general population. This concept was scarcely tested in patients with chronic kidney disease. We investigated the behavior of BPV parameters in a large cohort of older patients with CKD.
Methods: This retrospective cohort study included patients ≥ 75 years old with eGFR ≤ 60 ml/min. Three systolic and diastolic consecutive blood pressure (BP) measurements were obtained automatically per visit (short-term - 3 consecutive measurements) and across visits (long-term - across visits). We calculated: 1) standard deviation (SD); 2) coefficient of variation (SD divided by the BP average) and 3) variability independent of the mean (VIM). For each BPV parameter, patients were divided into four quartiles.
Results: We included 1,063 patients (17,363 measurements). For short-BPV: the higher systolic BPV (SD and VIM) was associated with older age, a lower proportion of males and a higher proportion of patients with pulse pressure (PP) > 40 mmHg. Higher diastolic BPV (SD and VIM) was associated with lower body mass index, lower eGFR and a higher proportion of PP > 40 mmHg (for SD). Bland-Altman plots revealed comparable results between short- and long-term BPV.
Conclusion: A higher BPV was associated with reduced renal function in older patients with chronic kidney disease. Our study also suggests that short- and long-term BPV can be used with similar results. Further studies are needed to confirm the association between BPV and outcomes and understand the physiological mechanisms underlying this correlation.

Introduction:
血压变异性（blood pressure variability, BPV）增加与普通人群中心血管事件的高风险相关。这一概念在慢性肾脏病（chronic kidney disease, CKD）患者中鲜有验证。我们在一大群老年CKD患者中研究了BPV参数的表现。

Methods:
本回顾性队列研究纳入了年龄≥75岁且估计肾小球滤过率（estimated glomerular filtration rate, eGFR）≤60 ml/min的患者。每次就诊时自动获取3次连续的收缩压和舒张压（血压，blood pressure, BP）测量值（短期——3次连续测量），并跨就诊获取（长期——跨就诊）。我们计算了：1）标准差（standard deviation, SD）；2）变异系数（SD除以BP平均值）；3）均值独立变异性（variability independent of the mean, VIM）。针对每个BPV参数，将患者分为四个四分位数。

Results:
我们纳入了1063例患者（17363次测量）。对于短期BPV：较高的收缩压BPV（SD和VIM）与年龄更大、男性比例更低以及脉压（pulse pressure, PP）>40 mmHg的患者比例更高相关。较高的舒张压BPV（SD和VIM）与更低的体重指数（body mass index, BMI）、更低的eGFR以及更高比例的PP>40 mmHg（针对SD）相关。Bland-Altman图显示短期和长期BPV的结果具有可比性。

Conclusion:
在老年CKD患者中，较高的BPV与肾功能降低相关。我们的研究还表明，短期和长期BPV可产生相似的结果。需要进一步研究来证实BPV与结局之间的关联，并理解这种相关性背后的生理机制。