Significant controversy exists as to the meaning of a low glomerular filtration rate (GFR) in the elderly. The goal of the study was to evaluate whether elderly patients with low GFR are at risk for anemia, hyperkalemia, acidosis, and hyperphosphatemia.
Veterans Affairs Medical Center
All patients over 65 years of age with chronic kidney disease (CKD) and a GFR between 15 and 60 mL/min/1.73m2.
Anemia was defined as a hemoglobin <10g/dL, hyperkalemia as a potassium >5.5mEq/L, acidosis as a bicarbonate <21mEq/L, and hyperphosphatemia as a phosphorus >4.6mg/dL. Multivariable logistic regression was used to evaluate whether age modifies the effect of low GFR on metabolic complications by including an interaction term between age and GFR in each model.
13874 veterans were included in the study. The average age was 79, the average GFR was 46.5; 3.1% had anemia, 2.5% hyperkalemia, 2.3% acidosis, and 4.4% had hyperphosphatemia. Lower GFR was associated with increased rates of metabolic complications across all age groups (odds ratio per 5mL/min/1.73m2 decrease in GFR in multivariable models was 1.21 for anemia, 1.26 for hyperkalemia, 1.45 for acidosis, and 1.72 for hyperphosphatemia). There was no significant interaction between age and GFR in models including only age and GFR or in multivariable models (p values for the age X GFR interaction term: 0.66 for anemia, 0.19 for hyperkalemia, 0.54 for acidosis, and 0.22 for hyperphosphatemia).
Elderly patients with CKD are at risk for anemia, hyperkalemia, acidosis, and hyperphosphatemia; age does not modify the relationship between GFR and development of metabolic complications. Elderly patients with low GFR should be monitored for metabolic complications, regardless of age.