Potok O Alison, Ix Joachim H, Shlipak Michael G, Bansal Nisha, Katz Ronit, Kritchevsky Stephen B, Rifkin Dena E
Division of Nephrology-Hypertension, University of California San Diego, San Diego, CA.
Veterans Affairs San Diego Healthcare System, San Diego, CA.
Kidney Med. 2022 Jan 25;4(3):100416. doi: 10.1016/j.xkme.2022.100416. eCollection 2022 Mar.
RATIONALE & OBJECTIVE: The difference in the estimated glomerular filtration rate based on cystatin C and that based on creatinine (eGFRDiff) is known to be associated with frailty and mortality. Creatinine is influenced by muscle mass, more so than cystatin C; we aimed to determine whether eGFRDiff is associated with muscle quantity and to what extent muscle quantity explains the relationship between eGFRDiff and poor functional status.
A cohort analysis of the health, aging, and body composition study (HABC).
SETTING & PARTICIPANTS: Overall, 2,970 HABC participants had their baseline serum creatinine level, cystatin C level, and body composition measured using imaging.
Estimated glomerular filtration rates (eGFRs) were calculated using Chronic Kidney Disease Epidemiology Collaboration equations (estimated glomerular filtration rate based on cystatin C [eGFR] and estimated glomerular filtration rate based on creatinine [eGFR]), and eGFRDiff was calculated as eGFR - eGFR.
The total thigh muscle area was evaluated using computed tomography. The health, aging, and body composition study physical performance battery was scored on a continuous scale (standing and walking tasks); poor functional status was characterized by the lowest quartile.
We used linear regression to model the cross-sectional association of eGFRDiff and muscle measures. We used logistic regression to evaluate the association of eGFRDiff with poor functional status.
The mean age was 74 ± 3 years; the eGFR, eGFR, and eGFRDiff was 72 ± 18, 68 ± 15, and 4 ± 14 mL/min/1.73 m, respectively. Compared with participants in the reference group (-10 < eGFRDiff ≤ 10 mL/min/1.73 m), those in the negative eGFRDiff group (≤-10 mL/min/1.73 m) were more likely to have comorbidities, a slower gait, and worse functional status. They had an approximately 14-cm smaller thigh muscle area in a fully adjusted model. Compared with the reference group, those in the negative group had 1.89-fold higher odds of poor functional status (unadjusted). This relationship was minimally attenuated after adjustment for thigh muscle, thigh fat area, appendicular lean mass, and limb fat mass, both individually and in combination.
The functional status outcome was specific to HABC. The muscle measures did not capture dynamic turnover.
The difference of eGFR - eGFR provides information on older adults' functional status, which is only partially explained by muscle quantity and quality.
基于胱抑素C的估算肾小球滤过率与基于肌酐的估算肾小球滤过率之间的差异（eGFRDiff）已知与衰弱和死亡率相关。肌酐比胱抑素C更容易受到肌肉量的影响；我们旨在确定eGFRDiff是否与肌肉量相关，以及肌肉量在多大程度上解释了eGFRDiff与功能状态不佳之间的关系。
对健康、衰老和身体成分研究（HABC）进行队列分析。
总体而言，2970名HABC参与者使用影像学测量了其基线血清肌酐水平、胱抑素C水平和身体成分。
使用慢性肾脏病流行病学协作组方程计算估算肾小球滤过率（eGFRs）（基于胱抑素C的估算肾小球滤过率[eGFR]和基于肌酐的估算肾小球滤过率[eGFR]），eGFRDiff计算为eGFR - eGFR。
使用计算机断层扫描评估大腿肌肉总面积。对健康、衰老和身体成分研究身体性能测试进行连续评分（站立和行走任务）；功能状态不佳的特征为处于最低四分位数。
我们使用线性回归对eGFRDiff与肌肉测量指标的横断面关联进行建模。我们使用逻辑回归评估eGFRDiff与功能状态不佳之间的关联。
平均年龄为74±3岁；eGFR、eGFR和eGFRDiff分别为72±18、68±15和4±14 mL/min/1.73 m²。与参考组（-10 < eGFRDiff≤10 mL/min/1.73 m²）的参与者相比，eGFRDiff为负值组（≤-10 mL/min/1.73 m²）的参与者更有可能患有合并症、步态较慢且功能状态较差。在完全调整模型中，他们的大腿肌肉面积小约14平方厘米。与参考组相比，负值组功能状态不佳的几率高1.89倍（未调整）。在分别或综合调整大腿肌肉、大腿脂肪面积、四肢瘦体重和肢体脂肪量后，这种关系仅有轻微减弱。
功能状态结局指标特定于HABC。肌肉测量指标未反映动态更新情况。
eGFR - eGFR的差异为老年人的功能状态提供了信息，而肌肉量和质量仅部分解释了这种差异。
