Anemia, a common complication of chronic kidney disease (CKD), is associated with poor prognosis. However, it is not completely clear whether this association is caused by anemia per se or other comorbidities. Whether different types of iron deficiency anemia can predict the outcomes of CKD remains unclear. The dataset from NHANES III was analyzed and Cox multivariate regression models and propensity score matching (PSM) method were used to evaluate the effect of anemia on mortality. Of 4103 patients with CKD, 14.6% had anemia. Among those with anemia, 38.8% had absolute iron deficiency (AID), and 19.8% had functional iron deficiency (FID). During the median follow-up time of 13.8 years, 2964 deaths and 804 cardiovascular deaths were observed. Anemia was robustly associated with a high risk of all-cause mortality in CKD patients after adjusting covariates by two multivariate regression models (Model 1: HR = 1.485, 95%CI:1.340-1.647, p < 0.001; Model 2: HR = 1.391, 95%CI:1.250-1.546, p < 0.001). In the PSM cohort, anemia was still an independent risk factor for all-cause mortality (Model 1: HR = 1.443, 95%CI: 1.256-1.656, p < 0.001; Model 2: HR = 1.357, 95%CI:1.177-1.564, p < 0.001). In the CKD population, anemia patients with FID had the highest risk of mortality than the other anemia groups (p < 0.05), while AID had a mortality rate similar to those without anemia (p > 0.05). In conclusion, anemia was associated with a worse prognosis in patients with CKD, which may be attributed to the higher mortality risk of FID rather than AID. AID wasn't associated with a higher mortality rate compared with CKD patients without anemia.
Keywords: CKD; Iron deficiency; NHANES III; all-cause mortality; anemia.