Supplementary Material for: Prevalence of Impaired Kidney Function in the German Elderly: Results from the Berlin Aging Study II (BASE-II)

<b><i>Background:</i></b> In aging populations with an ever-growing burden of risk factors such as obesity, diabetes, and hypertension, chronic kidney disease (CKD) is on the rise. However, little is known about its exact prevalence among elderly adults, and often albuminuria is not included in the definition of CKD. Moreover, novel equations for the estimated glomerular filtration rate (eGFR) have recently emerged, which have not been applied comprehensively to older adults. Data on CKD awareness among the elderly are sparse. <b><i>Objectives:</i></b> To determine the prevalence of CKD among older adults by eGFR and albumin/creatinine ratio (ACR), compare the performance of 6 established and novel eGFR formulas, explore risk factors, and determine the awareness of CKD in a large cohort of community-dwelling elderly from Germany. <b><i>Methods:</i></b> A total of 1,628 subjects from the Berlin Aging Study II (BASE-II) were included in this analysis (mean age 68.7 years; 51.2% female). Extensive cross-sectional data on sociodemographics, lifestyle, medication, and diagnoses were inquired during structured interviews and a medical examination, and blood and urine parameters were measured. <b><i>Results:</i></b> In all, 77.1% of the subjects had hypertension, 12.4% had diabetes, and 18.3% were obese. The prevalence of CKD strongly depended on the eGFR equations used: 25.4% (full age spectrum [FAS] equation), 24.6% (Berlin Initiative Study), 23.1% (Lund-Malmö revised), 19.3% (Cockcroft-Gault), 16.4% (Chronic Kidney Disease-Epidemiology Collaboration [CKD-EPI]), and 14.7% (Modification of Diet in Renal Disease [MDRD]). Of the subjects with an eGFR_FAS &lt;60 mL/min/1.73 m² and/or an ACR &gt;30 mg/g, only 3.9% were aware of having CKD. Polypharmacy, age, BMI, coronary artery disease, non-HDL cholesterol, and female sex were independently associated with CKD. <b><i>Conclusions:</i></b> CKD is prevalent among older adults in Germany, but awareness is low. The FAS equation detects higher rates of CKD than MDRD and CKD-EPI, which are most widely used at present. Also, when CKD is defined based on eGFR and albuminuria, considerably more people are identified than by eGFR alone. Finally, polypharmacy is associated with an increased risk for CKD in the elderly.

<b><i>背景：</i></b> 在肥胖、糖尿病、高血压等危险因素负担日益加重的老龄化社会中，慢性肾脏病（Chronic Kidney Disease, CKD）的患病率呈上升趋势。然而，目前针对老年人群CKD的确切患病率仍不明确，且CKD的定义往往未将白蛋白尿纳入其中。此外，近年涌现出多种新型估算肾小球滤过率（estimated glomerular filtration rate, eGFR）计算公式，但尚未在老年群体中得到全面应用。目前关于老年人CKD知晓情况的相关数据也极为匮乏。<b><i>研究目标：</i></b> 本研究依托德国大型社区居住老年人群队列，通过eGFR与白蛋白/肌酐比值（albumin/creatinine ratio, ACR）评估老年人群CKD的患病率，对比6种经典与新型eGFR计算公式的应用效能，探索CKD的潜在危险因素，并明确老年人群对CKD的知晓情况。<b><i>研究方法：</i></b> 本分析共纳入柏林老龄化研究II（Berlin Aging Study II, BASE-II）的1628名受试者，平均年龄68.7岁，女性占比51.2%。研究通过结构化访谈与医学检查收集受试者的社会人口学特征、生活方式、用药情况及疾病诊断等多维度横断面数据，并检测血液与尿液相关参数。<b><i>研究结果：</i></b> 总体而言，77.1%的受试者合并高血压，12.4%患有糖尿病，18.3%存在肥胖。CKD的患病率因所采用的eGFR计算公式不同存在显著差异：采用全年龄谱公式（full age spectrum, FAS）时患病率为25.4%，柏林倡议研究公式为24.6%，隆德-马尔默修订版公式为23.1%，科克罗夫特-高特（Cockcroft-Gault）公式为19.3%，慢性肾脏病流行病学协作组（Chronic Kidney Disease-Epidemiology Collaboration, CKD-EPI）公式为16.4%，肾脏病饮食改良研究（Modification of Diet in Renal Disease, MDRD）公式为14.7%。在采用FAS公式计算的eGFR<60 mL/min/1.73 m²且/或ACR>30 mg/g的受试者中，仅3.9%知晓自身患有CKD。多重用药、年龄、BMI、冠状动脉粥样硬化性心脏病、非高密度脂蛋白胆固醇及女性性别与CKD独立相关。<b><i>研究结论：</i></b> 德国社区老年人群中CKD患病率较高，但人群对CKD的知晓率极低。FAS公式检出的CKD患病率高于目前临床最常用的MDRD与CKD-EPI公式。此外，若同时基于eGFR与白蛋白尿定义CKD，检出的患者数量远多于仅通过eGFR单独定义的情况。最后，多重用药与老年人群CKD发病风险升高显著相关。