In older adults, data on the age-related course of GFR are scarce, which might lead to misjudgment of the clinical relevance of reduced GFR in old age.

To describe the course of eGFR in older adults and derive reference values in population-based individuals, we used the longitudinal design of the Berlin Initiative Study (BIS) with a repeated estimation of GFR over a median of 6.1 years of follow-up. In 2069 community-dwelling older individuals (mean inclusion age 80 years, range 70–99), GFR was estimated biennially with the BIS-2 equation, including standardized creatinine and cystatin C levels, sex, and age. We described the crude and adjusted course using a mixed-effects model and analyzed the influence of death on the GFR course applying joint models. GFR slopes were compared using GFR equations on the basis of creatinine and/or cystatin C.

We observed a decreasing, thus nonlinear, eGFR decline with increasing age in a population of old adults. The estimated 1-year slope for ages 75 and 90 diminished for men from –1.67 to –0.99 and for women from –1.52 to –0.97. The modeled mean eGFR for men aged ≥79 and women ≥78 was below 60 ml/min per 1.73 m². Multivariable adjustment attenuated slopes only minimally. Taking death into account by applying joint models did not alter the nonlinear eGFR decline. Using eGFR equations on the basis of creatinine only showed linear slope patterns in contrast to nonlinear patterns for equations including cystatin C.

The eGFR decline depended on sex and age and changed only marginally after multivariable adjustment but decelerated with increasing age. Equations including cystatin C demonstrated a nonlinear slope challenging the previously assumed linearity of the decline of eGFR in old age.

在老年人中，GFR 与年龄相关的数据很少，这可能导致对老年 GFR 降低的临床相关性的错误判断。

为了描述老年人的 eGFR 过程并得出基于人群的参考值，我们使用了柏林倡议研究 (BIS) 的纵向设计，并在中位 6.1 年的随访中重复估计了 GFR。在 2069 名社区居住的老年人（平均纳入年龄 80 岁，范围 70-99）中，每两年使用 BIS-2 方程估算一次 GFR，包括标准化肌酐和胱抑素 C 水平、性别和年龄。我们使用混合效应模型描述了粗略和调整后的过程，并应用联合模型分析了死亡对 GFR 过程的影响。使用基于肌酐和/或胱抑素 C 的 GFR 方程比较 GFR 斜率。

我们观察到，在老年人群中，eGFR 随着年龄的增长而下降，因此是非线性的。75 岁和 90 岁男性的估计 1 年斜率从 –1.67 降至 –0.99，女性从 –1.52 降至 –0.97。≥79 岁男性和≥78 岁女性的模型平均 eGFR 低于每 1.73 m ² 60 ml/min 。多变量调整仅最小程度地减弱斜率。通过应用联合模型将死亡考虑在内并没有改变非线性 eGFR 下降。使用基于肌酐的 eGFR 方程仅显示线性斜率模式，而包含胱抑素 C 的方程则显示非线性模式。

eGFR 下降取决于性别和年龄，在多变量调整后仅略有变化，但随着年龄的增加而减慢。包括胱抑素 C 在内的方程显示出非线性斜率，挑战了先前假设的老年 eGFR 下降的线性关系。