Low hemoglobin, independent of other health conditions puts older adults at risk for several adverse health outcomes associated with poor oxygen delivery including exhaustion, fatigue [8
], failing muscle strength [9
], and cognitive decline [5
]. The increased mortality risk for older adults with anemia is well documented [3
]. This risk is not accounted for by underlying disease [3
], suggesting anemia, alone, is a risk factor for death in older adults. Several of these studies also provide evidence that older adults who are not anemic by WHO standards, but have low-normal hemoglobin, still have higher mortality risk than non-anemic controls [4
]. Frailty has been associated with being African American [13
], and because anemia is more likely to affect non-Hispanic black older adults [2
], several investigators have looked more closely at anemia as a predictor of mortality for either blacks or whites. A recent follow up study assessed the relationship between hemoglobin concentration and a significant increase in the risk of death in both race groups in NHANES III [14
]. The authors concluded that the risk of death for non-Hispanic blacks increases significantly at 0.7g/dL below the WHO-defined hemoglobin limit, while the risk of death for non-Hispanic whites is 0.4 g/dL above the WHO-defined limit. The difference in hemoglobin concentration for the mortality “signal” in these two groups is similar to the overall difference in average hemoglobin between these groups and was not explained by variability in the cause or type of anemia. Similar results were reported for mortality rates of anemic black and white older adults in Chicago [12
]. These findings support more specific, stratified criteria for anemia in older adults based on race, in addition to gender and are especially important to consider when designing studies to treat anemia in these groups.
To investigate the impact of anemia on adverse clinical outcomes prior to death, Chaves and colleagues assessed whether WHO anemia criteria also identified women at risk for mobility difficulty [8
]. Using self-reported mobility difficulty scores and a performance-based summary score obtained from the Women’s Health and Aging Study, the authors showed that mobility scores improved for women as hemoglobin concentrations rose from 12 to 14 g/dL. They concluded that 12 or even 13 g/dL hemoglobin might not be sufficient for identifying women at risk for disability. Similarly, the prevalence of frailty in the Cardiovascular Health Study significantly increased as hemoglobin declined, even though hemoglobin concentration remained above the WHO cut-off for anemia [4
Strong relationships exist between anemia and the expected physiologic effects of reduced hemoglobin concentration such as reduced physical performance, fatigue, and declining muscle strength in the elderly [15
]. Low-normal hemoglobin above the WHO cut-off was associated with decreased hand grip strength, fatigue, and decreased quality of life in older community-dwelling adults in the United States [16
]. Anemic older adults were found to have lower muscle strength [9
] and lower muscle density [17
] than non-anemic controls in the InCHIANTI study. Even measurable declines in executive function [10
] and cognitive impairment [18
] are associated with anemia in older women.
Given that anemia affects between 10 and 20% of older adults and given that anemia is closely associated with impaired cognition, fatigue, disability, and mortality, the identification of effective strategies for the treatment of anemia in older adults seems to be an area worthy of intense biomedical investigation. However, the vast majority of the data is epidemiologic in nature and does not prove a causal role for anemia with respect to these poor health outcomes. Randomized, controlled clinical trials to improve hemoglobin concentration might provide evidence for a causal role and may positively impact physical performance and quality of life for older adults. Unfortunately, such studies have been severely hindered because the underlying cause of anemia in older adults varies widely and, most often, cannot be easily treated.