Worldwide Prevalence of Anemia. Causes of Anemia

According to the WHO, between 1990 and 1995 there are about 2 billion people with anemia in the world, half of whom have IDA (Allen et al, 2006). The prevalence of anemia has reached alarming figures in Africa (46%), Southeast Asia (57%), and in the eastern Mediterranean countries (45%) (Indian Council of Medical Research, 1989) (Table 1).

Table 1. Prevalence of anemia by WHO region

As for its distribution by age group, it is estimated that the prevalence of anemia reaches 50% of pregnant women and children aged 1-2 years, up to 25% of preschoolers, 40% of school-age children, 30-55% of adolescents, and 35% of nonpregnant women. Regardless of the age group, the risk of anemia is two- to sevenfold greater in developing compared to developed countries, particularly in rural areas (Galloway, 2003a, 2003b).

In a large study conducted in more than 80 countries supported by UNICEF, it was reported that an average of 45% in children less than 5 years old had iron deficiency. The prevalence was higher than 70% in 20 countries (Table 2) (UNICEF, 2004).

Table 2. Countries ranked by percentage of children estimated to be iron deficient, by region, 2000

Acute anemia has been associated with a higher risk for death in mothers and infants. There are negative consequences of ferropenic anemia on the cognitive and physical development of children and in the work performance of adults (Stoltzfus, 2001). The presence of anemia in surgical patients can increase the risk of postoperative morbidity and mortality.

In terms of disability-adjusted life years (DALYs), IDA accounts for approximately 25 million lost DALYs, or 2.4% of the overall total. Annually, IDA leads to 134 000 deaths of children, and indirectly, 841 000 maternal and perinatal deaths.

Causes of Anemia. Several factors are responsible for the development of anemia; among them, deficiencies of some micronutrients are probably the most common. Iron deficiency is the first nutritional cause, followed by deficiencies of folate, vitamin B₁₂, and vitamin A, alone or in combination. Deficiencies of other vitamins and minerals, such as vitamin B₆, vitamin C, riboflavin, and copper, have been implicated as causes of anemia, although there is little evidence that those deficiencies contribute significantly to the pathogenesis of anemia (Galloway, 2003a, 2003b; WHO/UNICEF, 2005).

Some pathologies produce anemia by other mechanisms. In tropical countries, a common cause of chronic blood loss are infestations by intestinal hematophagous parasites, such as ancylostoma and trichocephalus. Endemic malaria produces anemia as well. Environmental conditions play an important role in the development of anemia in susceptible subjects (Galloway, 2003a, 2003b; WHO/UNICEF, 2005) (Table 3).

Table 3. Causes of anemia

Besides the participation of iron in the synthesis of hemoglobin, anemia is involved in a large number of functions within the body, including the respiratory chain, phagocytosis, prostaglandin synthesis, and the cytochrome P450 system, among others (Langseth, 1996).