Anemia and its clinical consequences in patients with chronic diseases

Abstract

Anemia is not considered a serious clinical condition by the vast majority of physicians. Instead, it is thought to be either an insignificant finding in an otherwise healthy patient or a comorbidity that compounds the complexity of managing a patient with 1 chronic disease. Although the risks and benefits of treatment for nonnutritionally based anemia have been reasonably well documented, the magnitude of risk associated with untreated anemia remains largely unknown. The contribution of anemia to poor outcomes in chronically ill patients has been documented in many diseases to various degrees. 1 In patients with chronic kidney disease, for example, the impact of anemia on morbidity, mortality, and quality of life (QOL) has been extensively examined; numerous publications describing this patient population are available. For other chronic diseases, much less information has been published, and the available publications have not been collated and summarized. Therefore, this supplement to The American Journal of Medicine focuses on 6 areas in which there is a plausible expectation that anemia is likely to exist and to influence clinical outcomes independently, despite the previous lack of research data systematically gathered, evaluated, and synthesized. The systematic reviews presented herein contain a synthesis of the growing body of literature on both the prevalence of anemia and the effects of this condition on various clinical and functional outcomes, including mortality, morbidity, and QOL. The articles examine the impact of these issues on 6 key clinical areas: geriatrics, cancer, human immunodeficiency virus (HIV) infection, inflammatory bowel disease (IBD), rheumatoid arthritis, and surgery. (Although the role of anemia in congestive heart failure is gaining interest, the data from this emergent area of research lie beyond the scope of this review.) The evidence in aggregate indicates that anemia is an important, possibly independent, factor determining patient outcomes in these chronic disease states. Moreover, the evidence suggests that there is a critical need for a paradigm shift to the recognition of anemia as an important condition leading to significant consequences when it is not identified and effectively treated. Anemia, defined by the World Health Organization (WHO) as a hemoglobin concentration 130.0 g/L in men or 120.0 g/L in women, is more common than is generally realized. 2 The National Center for Health Statistics provides a conservative estimate, through self-reported data, of approximately 3.4 million Americans with anemia; women, African Americans, the elderly, and those with the lowest incomes exhibit the highest prevalences of anemia. 3 Derived from hemoglobin measures in a nationally representative sample, data from the second National Health and Nutrition Examination Survey (NHANES II) show that anemia is most prevalent in infants (5.7%), teenage girls (5.9%), young women (5.8%), and elderly men (4.4%). 4 The likelihood of anemia is even greater in certain elderly subpopulations. Prevalence estimates published in the geriatrics literature range from 2.9% to 61%, with the variations stemming from a number of factors: the anemia definition used, the setting of the study (e.g., hospitalized vs. community-dwelling elderly), and the clinical characteristics of the patients. The literature suggests that among the elderly, anemia is generally more common in men than women, perhaps because the hemoglobin levels used to define anemia are typically higher for men. Also clear from the literature is that the prevalence of anemia increases with age, even in geriatric populations; in fact, a number of studies found a particularly sharp increase in the prevalence of anemia for patients 85 years of age. Whereas the association of anemia and adverse outcomes such as weakness, fatigue, and falls is generally acknowledged in the elderly, very few studies have rigorously examined the impact of anemia on clinical, functional, and economic outcomes or on patient satisfaction.