Anaemia is a condition in which the blood has a decreased number of red blood cells.
It isn’t a diagnosis in itself in that it has many different causes which must be correctly identified in order to successfully treat the condition. It may also be the first indicator of a serious underlying problem such as a stomach ulcer, an autoimmune condition or cancer.
The main component of red blood cells is haemoglobin: the iron-rich molecule that gives blood its red colour. Haemoglobin helps red blood cells to carry oxygen from the lungs to the rest of the body.
Red blood cells, along with the other cellular components of blood such as white blood cells and platelets, are produced in the bone marrow (this is found in the centre of our bones). Red blood cells have a lifespan of 120 days, after which old cells are removed from the circulation.
Even though anaemia is strictly defined as “a reduced absolute number of circulating red blood cells”, measuring this isn’t practical or cost-effective, and tests are not widely available.
Anaemia is therefore also defined by a reduction in one or more of the major measurements of red blood cells: haemoglobin concentration (Hb), haematocrit (HCT) or red blood cell count.
Approximately 50% of anaemias occur as a result of insufficient iron in the body (iron deficiency), but this varies among population groups and in different areas.
Reasons for a low number of red blood cells
Essentially, the reasons for a low number of red blood cells generally fall into one of two categories:
- Under-production of haemoglobin, or production of abnormal haemoglobin or red cells by the bone marrow – for example, when the body is lacking in one of the ‘ingredients’ needed for its production (e.g. iron).
- Increased loss of red blood cells via excessive bleeding or the destruction of abnormal cells by the body.
Sometimes the cause of the anaemia is a combination of these factors. For example, in thalassaemia, the bone marrow produces dysfunctional haemoglobin, which in turn leads to the production of abnormal red blood cells that are removed early from the circulation.
If you have anaemia, the organs in your body don’t get enough oxygen-rich blood. As a result you may feel tired, weak, irritable and dizzy. You may have difficulty exercising due to shortness of breath, a rapid heartbeat or chest pain.
With severe or long-lasting anaemia, the lack of oxygen in your blood can damage your heart, brain and other organs in the body. Very severe anaemia, especially if it develops rapidly, may even cause death.
If it's suspected that you have anaemia because of your symptoms, your doctor’s examination, or from routine blood testing, a full blood count will be taken to confirm the diagnosis.
A full blood count can show any number of abnormalities, including:
- Low haemoglobin
- Reduced haematocrit: the percentage of a sample of blood comprised of red blood cells
- Reduced red cell count
- The “mean corpuscular volume” (MCV), a measurement of red blood cell volume, may be reduced. This may be one of the first indicators of anaemia before there’s a drop in haemoglobin.
Further testing will then be done to diagnose the underlying cause.
How common is anaemia?
Anaemia is a common condition that occurs across all age, racial and ethnic groups. Anaemia affects 1.62 billion people across the globe – approximately 25% of the population. The world’s poorest and least educated populations are often at greatest risk of exposure to the risk factors for anaemia.
Both men and women can have anaemia, but women of childbearing age are at higher risk as they lose blood through menstruation. Anaemia can also develop during pregnancy due to low levels of iron and folic acid in the blood, as well as in the period after birth due to blood loss during delivery.
Infants younger than two years are also at increased risk for anaemia because they may not get enough iron from their diet. Early weaning of infants onto cow’s milk (below one year of age) can lead to anaemia as the iron in the milk is poorly absorbed due to the presence of calcium. Infant formulas are supplemented with iron and provide adequate amounts.
South Africa has a relatively high prevalence of anaemia when compared to first-world countries such as the United States. The World Health Organization (WHO) estimated that 41% of South African children aged 6 months to 5 years had anaemia in 2011 (compared to 6% in the USA). It also estimated that 28% of all South African women of reproductive age (15 to 49 years) had anaemia in that year, compared to 12% in the USA.
Reviewed by Cape Town-based general practitioner, Dr Dalia Hack. October 2018.
- The different types of anaemia