Anemia in elderly patients: an emerging problem for the 21st century.

Anemia is a significant problem in elderly patients. Although many anemic elderly patients can be diagnosed with nutritional deficiency, anemia of chronic inflammation or comorbid diseases that explain their decreased hematocrit, the etiology of anemia in a significant fraction remains obscure. There is evidence to suggest that the hematopoietic stem cell displays increasing erythropoietin (EPO) resistance with age. EPO levels rise in elderly, nonanemic patients, and it is hypothesized that there is an interplay between this rising demand for EPO and the decreasing ability of the aging kidney to produce adequate hormone to meet that need. There is further considerable evidence that aging is associated with increased proinflammatory cytokine expression and that many of these cytokines can contribute to EPO insensitivity. Consequently, genetic variation in the expression of these proinflammatory cytokines may influence the development of anemia in elderly patients, both through induction of hepcidin expression (anemia of inflammation) and through cytokine suppression of erythroid colony formation. The impact of inflammatory mediators, EPO insensitivity, and other factors that may act on the hematopoietic stem cell to decrease erythropoiesis are under active study and should serve to elucidate the pathophysiology of this important cause of morbidity and mortality in elderly individuals. A better understanding of the pathophysiology of anemia in elderly patients should provide critical entry points for interventions that will improve survival and quality of life in the aging population.