The incidence of end-stage renal disease (ESRD) is increasing in the United States (US) population USRDS, and the prevalence of chronic kidney disease also appears to be increasing, in parallel with increased surveillance, routine reporting of estimated glomerular filtration rates (eGFR) with the MDRD equation, as well as increasing prevalence of hypertension and diabetes in the general population. These same etiologic factors are also increasing at the global level; the increasing prevalence of CKD in the US population mirrors what is happening at the global level.
There is an increasing realization that CKD is associated with cardiovascular outcome events, and that this association is more marked with more advanced CKD. This association has been described with short-term outcomes in patients with acute myocardial infarction, as well as longer term outcome measures, including mortality rates, hospitalization rates and cardiovascular event rates.
Anemia is frequently associated with CKD, and when present, serves as an independent risk factor for cardiovascular morbidity and associated mortality.
Abramson et al. reported that CKD and anemia (hemoglobin 12 gm/dl in women, and 13 gm/dl in men) were independent risk factors for stroke in a middle-aged community-based population in the Atherosclerosis Risk in the Community (ARIC) study, with a relative risk of 7.49 in those subjects who are anemic and had creatinine clearance 60 ml/min compared to the non-anemic participants with creatinine clearances > 60 ml/min. Similarly, the combination of anemia and CKD has a significant impact on survival after acute myocardial infarction in a study of Medicare recipients in Georgia. There are 3 large samples of patients in the US that provide estimates of the prevalence of CKD, with stratification according to the degree of impairment of kidney function: a) the Renal REGARDS cohort is the focus of our current efforts at the University of Alabama at Birmingham; b) the National Kidney Foundation Kidney Early Evaluation Program (KEEP); and c) the National Health and Nutrition Examination Survey (NHANES) 1999-2004. All three cohorts also provide prevalence estimates for co-morbidities such as cardiovascular and cerebrovascular disease.
The REGARDS and KEEP cohorts are older than the NHANES cohort, and have slightly greater prevalence of more advanced CKD (Stage 3) than the NHANES cohort. These cohorts are the undergoing longitudinal evaluation to prospectively determine the incidence of cardiovascular disease (MI and CHF), cerebrovascular disease (strokes and TIAs), and progressive CKD and ESRD. Based on self-reported history of co-morbidities, there appears to be an association between CKD (eGFR 60 ml/min/1.73 m2) and AMI and stroke, with an increased risk, adjusted for traditional (e.g., Framingham) risk factors of 35%. These prevalence estimates and associations will be converted to actual hazard ratios and detailed definition of the importance of traditional (i.e., systolic hypertension, diabetes, smoking, cholesterol, age, gender) and non-traditional (CKD stage, anemia, inflammation, ethnicity) risk factors for the occurrence of stroke, cardiovascular events and ESRD.
