Supplementary Material for: Hospitalization Risk among Older Adults with Chronic Kidney Disease

Introduction: Chronic kidney disease (CKD) risk staging is based on estimated glomerular filtration rate (eGFR) and albumin-creatinine ratio (ACR). However, the relationship between all-cause hospitalization risk and the current CKD staging system has not been well studied among older adults, despite a high prevalence of CKD and a high risk of hospitalization in old age. Methods: Among 4,766 participants of the Atherosclerosis Risk in Communities study, CKD was staged according to Kidney Disease Improving Global Outcomes (KDIGO) criteria, using creatinine-based eGFR (eGFRcr) and ACR. Incidence rates of all-cause hospitalization associated with each CKD risk group were analyzed using negative binomial regression. Additionally, cause-specific hospitalization risks for cardiovascular, infectious, kidney, and other diseases were estimated. The impacts of using cystatin C-based eGFR (eGFRcys) to estimate the prevalence of CKD and risks of hospitalization were also quantified. Results: Participants experienced 5,548 hospitalizations and 29% had CKD. Hospitalization rates per 1,000 person-years according to KDIGO risk categories were 208–223 (“low risk”), 288–376 (“moderately increased risk”), 363–548 (“high risk”), and 499–1083 (“very high risk”). The increased risk associated with low eGFR and high ACR persisted in adjusted analyses, examinations of cause-specific hospitalizations, and when CKD was staged by eGFRcys or eGFRcr-cys, a combined equation based on both creatinine and cystatin C. In comparison to eGFRcr, staging by eGFRcys increased the prevalence of CKD to 50%, but hospitalization risks remained similarly high. Discussion/Conclusion: In older adults, decreased eGFR, increased ACR, and KDIGO risk stages based on a combination of these measures, were strong risk factors for hospitalization. These relationships were consistent, regardless of the marker used to estimate GFR, but the use of cystatin C resulted in a substantially higher prevalence of CKD than the use of creatinine. Older adults in the population with very high risk stages of CKD have hospitalization rates exceeding 500 per 1,000 person-years.

引言：慢性肾脏病（CKD）的风险分期基于估算肾小球滤过率（eGFR）与白蛋白肌酐比（ACR）。然而，尽管老年人群中慢性肾脏病患病率较高且住院风险突出，但全因住院风险与现行CKD分期系统之间的关联尚未在老年群体中得到充分研究。
方法：本研究纳入社区动脉粥样硬化风险研究的4766名受试者，基于改善全球肾脏病预后组织（KDIGO）标准，采用基于肌酐的估算肾小球滤过率（eGFRcr）与ACR对CKD进行分期。采用负二项回归分析各CKD风险组的全因住院发生率。此外，还估算了心血管、感染性、肾脏及其他疾病的病因特异性住院风险。同时量化了基于半胱氨酸蛋白酶抑制剂C的估算肾小球滤过率（eGFRcys）在评估CKD患病率与住院风险中的影响。
结果：受试者中共发生5548例次住院，29%的受试者患有CKD。按改善全球肾脏病预后组织风险分类，每1000人年住院率分别为：低风险组208~223、中度升高风险组288~376、高风险组363~548、极高风险组499~1083。在校正后分析、病因特异性住院风险分析，以及采用eGFRcys或基于肌酐与半胱氨酸蛋白酶抑制剂C联合公式的eGFRcr-cys进行CKD分期时，低eGFR与高ACR相关的风险升高均持续存在。与eGFRcr相比，采用eGFRcys分期可使CKD患病率升至50%，但住院风险仍维持在较高水平。
讨论/结论：在老年人群中，eGFR降低、ACR升高，以及基于上述指标联合构建的改善全球肾脏病预后组织风险分期，均为住院的强危险因素。此类关联不受估算GFR所用生物标志物的影响，但采用半胱氨酸蛋白酶抑制剂C估算GFR时，CKD患病率显著高于采用肌酐估算的情况。人群中处于CKD极高风险分期的老年群体，其住院率超过每1000人年500例。