Introduction and Aims: Most, but not all, individuals demonstrate a decline in kidney function with increasing age. Age-related loss of GFR has been reported in the literature as approximately 1ml/min/1.73m2 per year. Creatinine and cystatin C are currently the two mostly used endogeneous renal markers for GFR estimation. It has been debated whether creatinine may be an insufficient renal marker in older age due to muscle wasting. Prevalence data on age-specific renal biomarker levels and albuminuria in individuals above the age of 70 are scarce.
Methods: The Berlin Initiative Study is a population-based cohort including participants at age 70 and older. The baseline-visit included an interview, short physical examination, and blood as well as urine analysis. 2070 participants with a mean age of 80.4 years were recruited from November 2009 to June 2011. In the current cross-sectional analysis we analyzed levels of standardized serum creatinine and cystatin C as well as urinary albumin-creatinine ratio (ACR >30 mg/g) in relation to age, categorized in 5-year age strata between 70 and >90 years.
Results: Main carachteristics of the study population are displayed in Both, creatinine (Figure 1)
Main characteristics of the BIS cohort (n=2070)
| Variable | % or mean (SD or range) | Total (n) |
|---|---|---|
| Age (years) | 80.4 (±6.7) | |
| Gender (female) | 52.6% | 1088 |
| Body mass index (kg/m2) BMI ≥30 | 26.5% | 547 |
| Blood Pressure Systolic (mmHg)Diastolic (mmHg) | 145 (74–245) 81 (44-149) | 2066 |
| Riskfactors Diabetes Mellitus Arteriael Hypertension Myocardial infarction Stroke | 26% 78.1% 13.8% 8.6% | 539 1617 286 177 |
| eGFR1 (mL/min per 1.73 m2) | ||
>60 (St. II) 30-60 (St. III) <30 (St. IV) | 62% 35.0% 2.9% | 1285 723 61 |
| Albuminuria (ACR) | ||
| <30 mg/g 30-300 mg/g >300 mg/g | 73% 22.7% 3.6% | 1512 469 74 |
| Variable | % or mean (SD or range) | Total (n) |
|---|---|---|
| Age (years) | 80.4 (±6.7) | |
| Gender (female) | 52.6% | 1088 |
| Body mass index (kg/m2) BMI ≥30 | 26.5% | 547 |
| Blood Pressure Systolic (mmHg)Diastolic (mmHg) | 145 (74–245) 81 (44-149) | 2066 |
| Riskfactors Diabetes Mellitus Arteriael Hypertension Myocardial infarction Stroke | 26% 78.1% 13.8% 8.6% | 539 1617 286 177 |
| eGFR1 (mL/min per 1.73 m2) | ||
>60 (St. II) 30-60 (St. III) <30 (St. IV) | 62% 35.0% 2.9% | 1285 723 61 |
| Albuminuria (ACR) | ||
| <30 mg/g 30-300 mg/g >300 mg/g | 73% 22.7% 3.6% | 1512 469 74 |
Main characteristics of the BIS cohort (n=2070)
| Variable | % or mean (SD or range) | Total (n) |
|---|---|---|
| Age (years) | 80.4 (±6.7) | |
| Gender (female) | 52.6% | 1088 |
| Body mass index (kg/m2) BMI ≥30 | 26.5% | 547 |
| Blood Pressure Systolic (mmHg)Diastolic (mmHg) | 145 (74–245) 81 (44-149) | 2066 |
| Riskfactors Diabetes Mellitus Arteriael Hypertension Myocardial infarction Stroke | 26% 78.1% 13.8% 8.6% | 539 1617 286 177 |
| eGFR1 (mL/min per 1.73 m2) | ||
>60 (St. II) 30-60 (St. III) <30 (St. IV) | 62% 35.0% 2.9% | 1285 723 61 |
| Albuminuria (ACR) | ||
| <30 mg/g 30-300 mg/g >300 mg/g | 73% 22.7% 3.6% | 1512 469 74 |
| Variable | % or mean (SD or range) | Total (n) |
|---|---|---|
| Age (years) | 80.4 (±6.7) | |
| Gender (female) | 52.6% | 1088 |
| Body mass index (kg/m2) BMI ≥30 | 26.5% | 547 |
| Blood Pressure Systolic (mmHg)Diastolic (mmHg) | 145 (74–245) 81 (44-149) | 2066 |
| Riskfactors Diabetes Mellitus Arteriael Hypertension Myocardial infarction Stroke | 26% 78.1% 13.8% 8.6% | 539 1617 286 177 |
| eGFR1 (mL/min per 1.73 m2) | ||
>60 (St. II) 30-60 (St. III) <30 (St. IV) | 62% 35.0% 2.9% | 1285 723 61 |
| Albuminuria (ACR) | ||
| <30 mg/g 30-300 mg/g >300 mg/g | 73% 22.7% 3.6% | 1512 469 74 |
and cystatin C (Figure 2)
values steadily increased from 0.86 (median) at the age of 70-74 to 1.16 mg/dl among >90 years and from 0.99 (median) to 1.42 mg/l, respectively. There was also a small increase in ACR with age from 7.5 mg/g (median) among the youngest to 11.2 mg/g among the oldest cohort participants.
Conclusions: In this cohort of elderly individuals serum levels of creatinine and cystatin C as well as levels of albuminuria increased with age (from 70 to 95 years). Prevalence data on kidney function and kidney damage (albuminuria) in population-based studies are essential for a better understanding of the situation in older age. In the future prospectively gathered data of the BIS will help to longitudinally observe development and progression of CKD in older age over several years and to evaluate the association of kidney deterioration and disease outcomes.
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