Recent reports have suggested that anemia is associated with adverse outcomes in patients with heart failure (HF), but were unable to adjust for a broad range of comorbid conditions. As a result, whether anemia is a truly independent predictor of risk or a marker of comorbid illness in these patients is unknown.
We analyzed medical records from the Centers for Medicare & Medicaid Services’ National Heart Care Project, a national sample of 50 405 patients 65 years and older admitted to acute care hospitals with a principal discharge diagnosis of HF between April 1, 1998, and March 31, 1999, or between July 1, 2000, and June 30, 2001. Multivariable logistic regression analyses were conducted to test whether hematocrit level was an independent predictor of all-cause mortality and HF-related readmission at 1 year.
In unadjusted analysis, lower hematocrit levels were associated with increased 1-year mortality and readmission for HF. Compared with patients with a hematocrit greater than 40% to 44%, those with a hematocrit of 24% or less had a 51% higher risk of death (relative risk [RR], 1.51; 95% confidence interval [CI], 1.35-1.68; P<.001) and a 17% higher risk of HF-related readmission (RR, 1.17; 95% CI, 1.01-1.34; P = .04). However, after adjustment for multiple comorbidities and other clinical factors, the association between lower hematocrit levels and increased 1-year mortality was markedly attenuated, even in those patients with the most severe anemia (hematocrit, ≤24% vs >40%-44%: RR, 1.02; 95% CI, 0.86-1.19; P = .85). The association between lower hematocrit values and HF-related readmission persisted after multivariable adjustment (hematocrit, ≤24% vs >40%-44%: RR, 1.21; 95% CI, 1.04-1.38; P = .01).
Although anemia is an independent predictor of hospital readmission, its relationship with increased mortality in HF patients is largely explained by the severity of comorbid illness. These findings suggest that anemia may be predominantly a marker rather than a mediator of increased mortality risk in older patients with HF.