Anemia

Anemia, also spelled anaemia in British English, is a blood disorder where the blood cannot carry oxygen as well as it should. This happens because there might be fewer red blood cells than normal, less of a special material called hemoglobin that carries oxygen, or problems with how hemoglobin works.

People with anemia often feel tired, weak, or short of breath, and they might have headaches or find it hard to exercise. In more serious cases, they might feel confused, dizzy, or even pass out. Anemia might not make someone look pale until it becomes quite bad. It can be a temporary problem or something that lasts a long time, ranging from mild to severe.

Anemia can happen for several reasons, such as losing blood, not making enough red blood cells, or breaking down red blood cells too quickly. Blood loss can occur during menstruation, from injuries, surgery, or even blood donations. Not making enough red blood cells can be due to a lack of iron, folate, or vitamin B₁₂, or because of certain genetic conditions. Breaking down red blood cells too fast can happen with infections like malaria or certain diseases that the body attacks itself.

Anemia is very common, affecting a large part of the world’s population. Iron-deficiency anemia is the most widespread type, especially in children, elderly people, and women who can become pregnant. It is one of the health goals set by the World Health Organization to improve global nutrition and fight hunger around the world.

Signs and symptoms

Symptoms of anemia can appear quickly or develop slowly. When anemia happens slowly, the body can adjust for a while, and you might not notice any problems until it gets worse. Common signs of mild anemia include feeling tired, weak, dizziness, headaches, shortness of breath, and pale or yellowish skin.

If anemia happens suddenly, often due to blood loss, symptoms can be more serious. These may include rapid heartbeat, low blood pressure, and confusion. The body tries to make up for the lack of oxygen by working harder, which can cause palpitations, angina if there is existing heart disease, and difficulty walking. In severe cases, the heart may beat very fast and the muscles may enlarge.

In babies, chronic anemia can affect growth and brain development. Pale skin from severe anemia might be seen in the palms of the hands and under the fingernails, but this can be hard to notice on darker skin. Other symptoms depend on what is causing the anemia. For example, iron deficiency might lead to unusual nail shapes, a sore tongue, hair loss, or a strong desire to eat non-food items like ice. Anemia from a lack of vitamin B₁₂ might cause memory problems and mood changes.

Diagnosis

Anemia can be defined in different ways. One simple way is to look at how well the blood can carry oxygen. Another way is to check the amount of a special material in the blood called hemoglobin, which helps carry oxygen. If there is less hemoglobin than expected, it may mean someone has anemia.

Doctors usually find out if someone has anemia by looking at a small sample of blood. They check the amount of hemoglobin and other important parts of the blood. To find out why someone might have anemia, more tests might be needed, such as checking for iron levels or looking at the family’s health history.

Causes

Anemia happens when the blood doesn't have enough red blood cells or hemoglobin to carry oxygen. Red blood cells are made in the bone marrow and live for about 100 to 120 days before being removed by the body.

Anemia can happen for several reasons:

• Not enough red blood cells being made. This can be due to poor diet, especially lack of iron, or problems with the body not using nutrients properly.
• Red blood cells being destroyed too quickly. This can happen because of inherited conditions or infections like malaria.
• Blood loss from injuries, heavy periods, or medical procedures.
• Too much fluid in the body, which dilutes the blood.

The most common cause worldwide is not enough iron in the diet, especially in poor areas. Other causes include inherited conditions and diseases like malaria.

Classification systems

Anemia is grouped based on the size of red blood cells. If the cells are smaller than normal, it is called microcytic anemia. If they are larger, it is called macrocytic anemia. When the size is normal, it is called normocytic anemia.

Microcytic anemia is often caused by not enough iron or certain long-term health problems. Macrocytic anemia can happen if there isn’t enough of certain vitamins, like B₁₂ or folate, or due to other health issues. Normocytic anemia may be due to blood loss or kidney problems.

Anemia can also be classified by how the body makes and breaks down red blood cells. If the body doesn’t make enough red blood cells, it is called hypoproliferative anemia. If red blood cells break down too quickly, it is called hemolytic anemia. Sometimes anemia happens suddenly due to blood loss from injury or surgery.

Transfusion dependence

Some people with anemia need regular blood transfusions to stay healthy. This is common in certain conditions like beta thalassemia. However, getting transfusions too often can cause too much iron to build up in the body, which may need special treatment.

Treatment

The way to treat anemia depends on finding out what is causing it.

If anemia happens suddenly, like from an injury or a sickness, doctors might give extra oxygen or blood to help until the person gets better. For anemia caused by not enough iron or vitamins in the diet, taking supplements or changing what you eat can help. Sometimes, special medicines or treatments are needed, especially for inherited conditions like sickle-cell disease. Blood transfusions, where blood is given to a person, are also used in certain cases to help with severe anemia.

Epidemiology

Anemia affects many people around the world, with about 24% of the global population experiencing it. Most of these cases are due to not enough iron. Women and girls are more likely to have anemia than men and boys, especially during their reproductive years.

Anemia is more common in older people and can affect up to 17% of those over 65 years old in developed countries. Young children, especially under five years old, are also at risk. Certain areas, like sub-Saharan Africa, have higher rates of anemia, often linked to infections such as malaria. Pregnant women are also more likely to develop anemia, especially if they have malaria.

History

People have known about severe anemia for thousands of years. Signs of it were found in ancient bones from Thailand that are about 4000 years old.

In 1674, a scientist named Antoni van Leeuwenhoek was the first to describe red blood cells. Later, in 1840, another scientist discovered hemoglobin, the part of blood that carries oxygen. By the late 1800s, scientists had created tools to measure blood and understand anemia better. Today, we know that iron in our blood is very important for health.