Unexplained Anemia in the Elderly.

The prevalence of anemia increases with advancing age, and despite thorough investigation, approximately one-third will be classified as "unexplained." Unexplained anemia (UA) is typically hypoproliferative, normocytic, and with low reticulocyte count. Serum erythropoietin levels are lower than expected for degree of anemia. Chronic inflammation, low testosterone levels, malnutrition, and possibly nascent myelodysplasia are variably contributing factors. No clearly established beneficial treatment strategy has been established, but the association of UA with a wide range of adverse outcomes, including impaired quality of life, physical function, and mortality, is sufficiently compelling to justify expanding clinical research focused on basic and clinical aspects.