What is Anemia?
Anemia is a word almost everyone has heard—and you may have a reasonable idea of what anemia feels like: low energy, poor stamina, and fatigue. But what exactly is anemia? What causes it? And how does it affect our children?
A basic understanding of the body's oxygen delivery system sets the stage for a discussion about anemia. All human tissue—every organ, every cell—needs a constant supply of oxygen to survive. Doctors often use the analogy of a freight train to explain the body's way of delivering oxygen. Consider the circulatory system—all of our blood vessels are like a vast network of train tracks upon which courses a train with many boxcars (red blood cells), each carrying a load of oxygen bound by molecules of hemoglobin. Propelling it all along is the job of the heart.
Anemia, then, is when the body suffers a shortage of those "boxcars," or red blood cells. It is described using a value called the hematocrit, which, roughly, is the percentage of a certain volume of blood (for blood has many other components) taken up by red cells. Another way of talking about it is by using the hemoglobin concentration—those molecules inside the red cell that bind and then release oxygen. Normal values vary with the age and the sex of a person. Babies, for example, are born with high hemoglobin levels. Extra hemoglobin is needed before birth to compensate for the lower oxygen environment of the uterus. Such an amount is no longer needed after birth, and hemoglobin levels naturally fall, reaching a low at six to eight weeks. Throughout childhood, levels climb slightly, then increase in puberty (more so in males than in females). Levels then stay relatively constant throughout adulthood.
The consequences of anemia, in an otherwise healthy child, are related to how severe it is. Early signs can be very subtle. A child may just be a little more irritable than usual. He may tire easily or may become short of breath sooner than his friends. His skin may look pale. If red cells are being destroyed too quickly, he may develop a yellow hue first in the whites of his eyes, then in his skin. As the anemia becomes more severe, the heart will try to compensate for the lack of red cells by pushing what blood there is around faster and the heart rate will increase, as will the rate of breathing. In critical anemia, with massive blood loss for example, the heart will not be able to compensate, the tissues will be starved of oxygen, and damage—even death—can occur.
Though this sounds scary, the vast majority of anemic children in America show no symptoms at all. Anemia is largely a silent disease. For this reason, physicians need to actively screen for anemia. We do this initially with children between nine and 12 months of life (a time of life when anemia due to dietary causes becomes more common) with a routine blood test. Why bother to pick up anemia when it is even too mild to cause symptoms? Because doctors don't yet know the full consequences of anemia for the growing brain. Recent studies compared young children with and without iron-deficiency anemia and found a measurable decline in the IQ of iron-deficient anemic children compared to non-anemic children. Yet even more alarming, those IQ points weren't recovered when the anemia was corrected! So the policy in the United States is to begin actively looking for anemia in late infancy, again in the toddler years, throughout childhood as necessary, and once more in the mid-adolescent.