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

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.

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.

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.

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 eGFRFAS <60 mL/min/1.73 m2 and/or an ACR >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.

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.