The term ‘anaemia’ is derived from the ancient Greek word ‘anaimia’, which means ‘lack of blood’. Unlike fever, which is your body’s response to an infection, anaemia is the manifestation of a disease. Multiple diseases can cause anaemia through various mechanisms. Anaemia affects a large percentage of people worldwide (especially in developing countries), which can result in a significant rise in medical care costs.
Anaemia is defined as a condition in which a body has an insufficient amount of haemoglobin (less than 13.5 g/dL in men and less than 12 g/dL in women), red blood cells (RBCs) (below 41% in men and 36% in women), or haematocrit (below 41% in men and 36% in women). The lower limits of the normal range for these components may differ depending on the ethnic background, gender, and age.
Anaemia reduces the blood’s oxygen-carrying capacity, resulting in tissue hypoxia (inadequate amount of oxygen in tissues).
According to the National Cancer Institute, anaemia is classified as follows:
- Mild: Haemoglobin levels range from 10 g/dL to 12 g/dL for women and 13.5 g/dL for men.
- Moderate: Haemoglobin levels range from 8 to 10 g/dL.
- Severe: Haemoglobin levels are between 6.5 and 7.9 g/dL.
Haemoglobin levels below 6.5 g/dL are life-threatening.
Anaemia is classified into two types: acute anaemia and chronic anaemia. Acute anaemia is primarily caused by a sudden loss of blood, also known as haemolysis. Chronic anaemia is much more common than acute anaemia and is caused by a variety of factors.
Causes of Anaemia
Anaemia has many causes, but the majority of them can be grouped into three main mechanisms as follows:
- Loss of the blood (excessive bleeding)
- Abnormal RBC production
- Excessive RBC destruction
Excessive bleeding can result in anaemia.
Bleeding can happen suddenly during surgery or due to an injury. Sometimes, bleeding is slow and repetitive (chronic bleeding). Chronic bleeding can be caused by digestive or urinary tract abnormalities, which include:
Gastrointestinal conditions, such as ulcers, haemorrhoids, gastritis (gastric inflammation), and cancer
Ulcers and gastritis resulting from nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen
A woman’s period, particularly if she has a heavy menstrual flow. This may be related to fibroids.
Chronic bleeding typically results in low iron levels, exacerbating anaemia.
Anaemia caused by an inadequate production of RBCs
Anaemia can occur when your body is unable to produce a sufficient number of RBCs. Many essential nutrients are required for the production of RBCs. Vitamin B12, iron, and folic acid (folate acid) are the most important components for RBC production. However, the body also requires trace amounts of copper and a balance of hormones, particularly of erythropoietin, a hormone which stimulates RBC production. Without all these hormones and nutrients, RBC production becomes slow and insufficient, or the RBCs become malformed and thus cannot transport oxygen efficiently.
The following conditions are linked to this cause of anaemia:
- Problems with stem cells and bone marrow
- Anaemia caused by iron deficiency
- Sickle cell anaemia
- Anaemia caused by a deficiency of vitamins, specifically folic acid or B12.
Problems with your bone marrow and stem cells
Few of the stem cells produced by your bone marrow develop into RBCs. If a sufficient number of stem cells is not available, if stem cells do not function properly, or if these cells are replaced by other cells, such as cancer cells, anaemia can be contracted. There are different types of anaemia caused by issues related to bone marrow or stem cells that include:
Aplastic anaemia: This anaemia occurs when there are insufficient or no stem cells because of damage to the bone marrow caused by chemotherapy, radiation therapy, medications, infection, or your genes.
Thalassemia: It is a hereditary anaemia caused by the faulty formation of haemoglobin on a molecular level due to which your body produces a very small number of RBCs. This anaemia can vary from mild to life-threatening; Cooley’s anaemia is the most severe form of this condition.
Poisoning by lead: Lead is toxic to your bone marrow and leads to a decrease in RBC count. Lead poisoning can occur when adults are exposed to lead at a workplace, when children consume lead paint chips, or when people come into contact with lead through foods cooked in improperly glazed pottery.
Anaemia due to a deficiency of iron
This anaemia occurs when your body does not have sufficient amounts of the mineral iron, which is required by your bone marrow to produce haemoglobin, the component of RBCs that transports oxygen to all parts of your body. There are several reasons that cause iron-deficiency anaemia, including:
- A diet deficient in iron, particularly in vegetarians and vegans, infants, children, and teenagers
- Certain medications, foods, and caffeinated beverages
- Crohn’s disease or surgery involving removal of a portion of the small intestine or stomach
- Pregnancy and breastfeeding, which deplete iron levels in the body
- Menstrual bleeding
- Chronic, slow bleeding, usually from the gastrointestinal tract
Sickle cell anaemia: It is a genetic disorder in which normally round RBCs become crescent-shaped (half-moon-shaped).
Vitamin-deficiency anaemia: This type of anaemia can develop if you are not getting sufficient amounts of vitamin B12 and folic acid, the two vitamins required for the formation of RBCs. The anaemia of this type can be caused by vitamin B12 deficiency: If you eat very little or no meat products, you may not receive sufficient amounts of B12. You may not get sufficient folate if you overcook your vegetables or do not eat enough of them.
Some other types of vitamin-deficiency anaemia include:
- Megaloblastic anaemia: This is caused by a deficiency of folate, vitamin B12, or both.
- Pernicious anaemia: This is a condition in which your body does not absorb enough vitamin B12.
Alcohol abuse, medication, and intestinal illnesses are some of the other causes of vitamin deficiency, which can lead to this type of anaemia
Anaemia due to other chronic conditions
This anaemia typically occurs as a result of chronic inflammation because inflammatory proteins inhibit the production of new RBCs in the bone marrow in various ways. This type of anaemia can be caused by the following conditions:
- Kidney disease (advanced stage)
- Long-term disorders that include diabetes, lupus, cancer, infection, and rheumatoid arthritis
Anaemia caused by RBC destruction
Anaemia can also result from the destruction of an abnormally large number of RBCs. RBCs normally live for about 120 days. Scavenger cells inside the spleen, liver, and bone marrow detect and degrade RBCs that have not reached the end of their life span. When RBCs are destroyed too soon (haemolysis), your bone marrow tries to compensate for the loss by making new cells quickly. Haemolytic anaemia occurs when the destruction of RBCs exceeds their production. This condition could be present at birth or develop later in life.
The reasons for haemolytic anaemia are not always clear, but they may include:
- An attack on the immune system. This can be encountered by anyone, including a baby still within the womb or a new-born, which is referred to as ‘new-born haemolytic disease’.
- Conditions that can be hereditary, including thalassemia, sickle cell anaemia, and thrombotic thrombocytopenic purpura (TTP).
- Enlarged spleen: In rare cases, this can trap your RBCs and kill them too soon.
- Infectious diseases, medications, snake venom, or even certain foods can all put a strain on your body.
- Vascular grafts, artificial heart valves, cancers, severe burns, exposure to certain chemical compounds, clotting disorders, and severe hypertension can lead to this anaemia.
- Toxins from advanced kidney or liver diseases can cause haemolytic anaemia.
Risk factors of anaemia
The following factors increase your risk of anaemia:
• Diet: You are at risk of developing anaemia if your diet is consistently low in iron, vitamin B12, folate, and copper.
• Intestinal conditions: Anaemia is more likely if you have an intestinal illness that affects the absorption of nutrients in your small intestine, for instance, Crohn’s disease or celiac disease.
• History: If you have a family history of a hereditary anaemia, such as sickle cell anaemia, you may be more susceptible to the condition.
• Chronic diseases: You may be at risk of anaemia from a chronic disease if you have cancer, kidney problems, or any other chronic condition. These conditions may result in an inadequate production of RBCs. Moreover, a gradual and chronic loss of the blood from an ulcer or due to any other issues within your body can decrease your body’s iron stores, resulting in iron-deficiency anaemia.
Do headaches cause anaemia?
Although headaches do not cause anaemia, they have been linked to several types of anaemia, including iron-deficiency anaemia, vitamin-deficiency anaemia, and sickle cell anaemia. Regardless of the source, headaches from anaemia occur for the same basic reasons of anaemia: your organs do not receive sufficient blood to operate normally. When this occurs, the blood vessels in your brain enlarge and end up causing pressure that causes a headache.
What causes anaemia?
Anaemia is caused by three factors: blood loss, inadequate production of red blood cells, and rapid red blood cell destruction.
Does a deficiency of iron cause anaemia?
Yes, it is one of the common causes of iron-deficiency anaemia.
Does having less haemoglobin cause anaemia?
Haemoglobin is the component of RBCs that allows red blood cells to transport oxygenated blood to all parts of your body. If you do not consume sufficient amounts of iron or if you lose more iron than your body is able to produce, your body will not generate enough haemoglobin, and iron-deficiency anaemia will develop.