- Anemia occurs commonly and is associated with poor outcomes in the elderly. In about a third of anemia cases in older people (over age 65), the cause of anemia is unexplained. Anemia in older adults may be caused by the bone marrow's inability to produce red blood cells fast enough to replace older red blood cells that have died. Researchers want to look at unexplained anemia by studying the life span of red blood cells in younger adults and older adults. To do so, a vitamin called Biotin will be used as a marker on the red blood cells.