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Anemia

Description

An in-depth report on the types, diagnosis, treatment, and prevention of anemia.

Alternative Names

Iron deficiency; Pernicious anemia

Risk Factors

Although nutritional iron-deficiency anemia has declined in industrialized nations, it affects an estimated 2 billion people worldwide. Even in the U.S., iron deficiency is the most prevalent nutritional deficiency. It is highly associated with poverty. People in lower socioeconomic groups have double the risk of those who are middle or upper class.

Among Americans with iron deficiency anemia, young children have the highest risk followed by premenopausal women. Adolescent and adult men and postmenopausal women have the lowest risk. Men, in fact, are at risk for iron overload, probably because of their higher meat intake.

General Risk Factors for Anemia in Infants and Children. Up to 20% of American children and 80% of children in developing countries become anemic at some point during their childhood and adolescence. Iron deficiency is the most common cause in children, but other forms of anemia, including hereditary blood disorders, can also cause anemia in this population. African-American children have the highest rates of anemia (about 25%) while other ethnic groups have an incidence under 20%.

Iron deficiency affects about 9% of children younger than 2 years. About 3% of children in this age group are anemic as a result. Children in lower-income homes are at higher risk than those in higher income homes. In a study of low-income children, ages 6 months to 5 years, the prevalence of anemia was over 10%, and was nearly 18% in children younger than 2 years. However, children in any income group can develop iron deficiency.

Young children 9 - 18 months have the highest risk for iron deficiency anemia in the U.S. Such children also are at great risk for problems in mental development from anemia. Infant boys may have 10 times more risk than baby girls. In general, full-term infants who are breastfed by their mothers have sufficient iron stores for their first 6 months of life. After that, they must rely on other sources for iron.

Iron-deficiency anemia in infants and small children can be due to one or more of the following factors:

• Stopping breast-feeding too early or using formula that isn't iron-fortified.
• Bottle-feeding too long. Studies indicate that the longer children are bottle-fed, the greater the risk for iron-deficiency and anemia. Toddlers 12 months and older should not drink more than 2 cups of milk a day. Cow’s milk is good for children, but it does not contain enough iron. Too much milk can decrease children’s appetite and prevent them from eating the iron-rich food they need. When babies who are bottle-fed are 7 - 9 months old, they should be weaned from bottles and given sippy cups. By the age of 12 months, all children should be using a cup instead of a bottle.
• Toddlers’ preferences for iron-poor food. Parents should make sure that their children eat iron-rich foods such as beans, meat, fortified cereals, eggs, and green leafy vegetables

Better social services and more accurate ways of diagnosing and monitoring anemia are needed in these high-risk groups. There is still considerable debate on how to define iron deficiency and anemia in infants. New research suggests that a reticulocyte hemoglobin content (CHr) test may be better than a standard hemoglobin test for detecting iron deficiency in babies. Reticulocytes are immature red blood cells. The CHr test measures the amount of hemoglobin in these cells.

Risk Factors for Anemia in Premenopausal Women. In a major government study, 9 - 16% of adolescent and adult women under 49 years were iron deficient. Hispanic American and African-American women had double the prevalence of Caucasian women. The risk for anemia in adolescent girls is about 3%. Anemia is generally mild in young women, however, and is more likely to occur with one or more of the following conditions:

• Heavy menstruation for longer than 5 days
• Abnormal uterine bleeding, such as from fibroids
• Pregnancy. About 20% of women in industrialized countries have iron deficiency during pregnancy. Multiple pregnancies and births significantly increase the risk.

Risk Factors for Anemia in Older Adults. Although studies have reported various estimates on the prevalence of anemia in older adults, one recent survey suggested that anemia affects approximately 10% of adults aged 65 years and older, and more than 20% aged 85 years and older. The causes of anemia in older adults were equally distributed among nutritional deficiencies, chronic inflammatory disease, chronic renal disease, and unexplained anemia. Most cases were mild.

People with Alcoholism

People with alcoholism are at risk for anemia both from internal bleeding and vitamin B deficiencies.

People with Iron-Poor Diets

Although most Americans probably consume too much iron in their diets, some people may be at risk for diet-related iron deficiencies:

• People whose diets are high in processed foods and lack any meat
• Strict vegetarians. Vegetarians who avoid all animal products may have a slightly higher risk for deficiencies in iron and some B vitamins. Although dried beans and green vegetables often contain iron, it is less easily absorbed from plants than from meat. Fortunately, most commercial cereals are fortified with vitamin B12 and folic acid (the synthetic form of folate).

Chronic or Critical Illnesses

Anyone with a chronic disease that causes inflammation or bleeding is at risk for anemia. Critical illness in the intensive care unit is also highly associated with anemia.

Athletes

Working out regularly may cause some iron loss, which is comparable to that from menstruation and rarely worrisome. One 2000 study suggests that dietary choices may account for most cases of sports anemia. Intense, sustained exercise, such as that performed by marathon runners, may cause a condition called sports anemia, which may be due to slight gastrointestinal bleeding, damaged red blood cells, low iron intake, or poor intestinal absorption of iron.

Anemia and the Pregnant Woman Iron deficiency occurs in 20% of pregnant women in developed countries. Even worse, 50% or more of women in nonindustrialized nations become iron deficient, and between 30 - 50% are deficient in folic acid. Severe anemia is associated with a higher mortality rate among pregnant women. Mild-to-moderate anemia, however, does not pose any elevated risk. Pregnancy increases the risk for anemia in different ways: It increases the body's demand for folic acid and, therefore, poses a risk for deficiencies and an increased risk for megaloblastic anemia. Low levels of folate during pregnancy increase the risk of neural tube defects in newborns. It increases the body's demand for iron, thus posing a risk for iron deficiency anemia. Pregnant or nursing women require 30 mg of iron per day. Maternal iron deficiency anemia is associated with increased weight or size of the placenta, a condition that may later pose a risk for high blood pressure in the offspring. Pregnant women with low hemoglobin levels (the iron-bearing component in the blood) have an elevated risk for pre-term or low birth weight infants. Pregnancy is also associated with fluid retention, which in turn may produce high volumes of plasma (the fluid component of blood). This can dilute red blood cells, which may lead to anemia. After delivery, heavy bleeding, which occurs in 5 - 10% of women who have given birth, can cause symptoms of anemia. Diagnosing of Iron Deficiency During Pregnancy A diagnosis of iron deficiency is problematic in pregnant women. The standard test is a measurement of ferritin levels, which are low in most people with iron deficiency. Pregnant women, however, may have high ferritin blood levels into their third trimester but still be iron deficient. A newer test that measures a factor called serum transferrin receptor may prove to be a useful way of diagnosing iron deficiency in women. Researchers are also investigating Doppler ultrasonography as an imaging technique for detecting anemia in the fetus. Traditionally, fetal anemia is diagnosed through amniocentesis. Doppler ultrasonography is a non-invasive method that does not risk causing a miscarriage or a worsening of fetal anemia. Preventing Anemia in Pregnant Women Iron Supplements. For the past 40 years, iron supplements have been recommended for all pregnant women. This practice has been challenged recently, however. There is no clear-cut evidence that the mild iron deficiency in most pregnant women experience is harmful. In addition, iron supplements cause gastrointestinal side effects and may not be completely harmless. Some experts suggest iron supplements for the following women: All pregnant women whose hemoglobin levels are less than 11 g/dl, and Pregnant women whose serum ferritin levels are low beginning in their 20th - 24th weeks of pregnancy. Vitamin Supplements. Women who are trying to conceive, who are pregnant, and who are breastfeeding should take 400 mcg of folic acid a day. They should be sure this is folic acid and not folate. Folate is the natural form of folic acid, but 400 mcg supplements of folate are half as potent as the same dose of folic acid. Pregnant and nursing women who are vegetarians should be sure to have supplements of folic acid and other B vitamins as well, since many of these nutrients are found primarily in animal products. Vitamin B12 deficiencies during pregnancy can also produce anemia in both mother and child. Diets Rich in Vitamin C. Eating foods rich in vitamin C can help absorb iron. Treating Anemia During Pregnancy Pregnant women who become anemic and require treatment may be given oral iron supplements or transfusions in severe cases. Intravenous iron sucrose is a newer form of IV iron and may prove to be effective and safe for pregnant women with anemia.

• Review Date: 1/17/2007
• Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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