More than one-quarter of the world's population is anemic. Approximately one-half of this burden is a result of iron deficiency anemia, being most prevalent among preschool children and women. The diagnosis, prevention, and treatment of iron deficiency is obviously a major public health goal, especially in low- and middle-income countries.
The development of iron deficiency, and the rapidity with which it progresses, is dependent upon the individual's initial iron stores, which are, in turn, dependent upon age, sex, rate of growth, and the balance between iron absorption and loss. The generally lower value for iron stores in adult women, for example, reflects the composite effect of menstrual losses (approximately 1 mg of iron loss per day), lower caloric intake, use of supplemental iron, and iron losses associated with pregnancy and lactation (approximately 1000 mg each for pregnancy, delivery, and nursing).
Data from the Third National Health and Nutrition Examination Survey (NHANES III; 1988 to 1994) indicated that iron deficiency anemia was present in 1 to 2 percent of adults (table 1) . Iron deficiency without anemia was more common, occurring in up to 11 percent of women (most often premenopausal) and 4 percent of men. In this survey, the prevalence of iron deficiency anemia was significantly higher in older adults, being between 12 and 17 percent in persons 65 years and older [2,3]. (See "Anemia in the older adult", section on 'Iron deficiency anemia'.)
The major causes, stages, and diagnosis of iron deficiency in adults will be reviewed here. These issues are best understood if the reader first reviews the regulation of normal iron balance. (See "Regulation of iron balance".)
The treatment of iron deficiency and issues concerning iron balance in children and adolescents are discussed separately. (See "Treatment of the adult with iron deficiency anemia" and "Iron deficiency in infants and young children: Screening, prevention, clinical manifestations, and diagnosis" and "Iron requirements and iron deficiency in adolescents".)