EFFECT OF AGE ON HEMATOPOIESIS IN MAN

Abstract

The cause of anemia in healthy elderly subjects can usually not be identified. Hematopoiesis was examined in 18 healthy elderly subjects with unexplained anemia, and in 15 young and 15 healthy elderly individuals without anemia. No reduction in circulating testosterone was noted, making decreased androgen levels an unlikely cause for the anemia. The 2,3 diphospho-glycerate (2,3DPG) levels in the anemic subjects were significantly higher than their corresponding controls. This suggests that the anemia was pathologic, as no increase would be expected if the low Hb was a physiologic adjustment to age. The anemia was associated with a reduction in marrow normoblast and CFU-E [erythroid colony-forming unit] number, but no decrease in BFU-E [erythropoietic burst forming cell] levels was seen. The mechanism of the anemia apparently is a decrease in stem cell proliferation. This could be caused by a reduction in circulating erythropoietin or a defect in end organ response. A 2nd possibility is that a basic cellular abnormality exists. The presence of an overall reduction in hematopoiesis in anemic elderly (decreased peripheral blood counts, reduced marrow myeloid precursors, and CFU-C [colony forming cell] levels) makes this especially likely. The abnormality may be caused by a mechanism unrelated to the aging process. That nonanemic elderly also have reductions in hematopoiesis suggests that age contributes to the defect.