Risk of Anemia in Patients with Newly Identified Chronic Kidney Disease - A Population-Based Cohort Study

Purpose: Anemia is prevalent in patients with chronic kidney disease (CKD), but the longitudinal risk of anemia in patients with newly identified CKD is unknown. We therefore examined the risks of experiencing anemia in persons with newly identified CKD. Patients and Methods: This cohort study included adult patients with newly identified CKD stages 3-5 defined by an estimated glomerular filtration rate (eGFR) level <60 mL/min/1.73m(2) (at least two measurements >= 90 days apart) ascertained from a population-based registry with complete laboratory test results in Northern Denmark (population similar to 2.2 million) during 2009-2016. We calculated 1) cumulative incidence (risk) of anemia [hemoglobin <12/<13 g/dl in women/men] by CKD stage, and 2) adjusted hazard ratios (HRs) of anemia using Cox regression analyses. Results: We identified 55,940 distinct individuals with newly identified CKD stages 3-5 and no prevalent anemia [n=41,958 patients in stage 3a, n=17,875 in stage 3b, n=5182 in stage 4, and n=931 in stage 5]. After one year, 42.3% (95%-confidence interval [CI]: 41.9-42.7) of patients with CKD stages 3-5 had newly measured anemia, increasing to 67.7% (95%-CI: 67.2-68.2) after five years. The absolute and relative anemia risk increased markedly with higher CKD stages. The adjusted HR of any anemia was 5.42 (95%-CI: 5.09-5.77) in patients with CKD stage 5 compared to patients with CKD stage 3a. Conclusion: Patients with newly identified CKD stages 3-5 have a substantial risk of anemia, increasing with higher CKD stages. This study underlines that clinical awareness of anemia risk is important in patients with newly identified or progressed CKD.