Anaemia Fact Sheet

Red blood cells (RBC) contain haemoglobin (HGB), a protein that enables oxygen to be carried from the lungs to the body. When the number of RBCs is reduced, or they are not healthy, the blood cannot carry a sufficient amount of oxygen. An inadequate supply of oxygen in the tissues causes the symptoms associated with anaemia.

Prevalence

Anaemia is a serious global health concern, predominantly affecting children and pregnant women. The World Health Organization (WHO) estimates that 42% of children under age 5 and 40% of pregnant women around the world suffer from anaemia. In 2021, data showed that the prevalence was 31.2% for women and 17.5% for males.

Data collected between 1993-2005 from the WHO Vitamin and Mineral Nutrition Information System found that an estimated global prevalence of anaemia was 24.8% (1.62 billion people). Results from previous and current Global Burden of Disease Studies found that there were 1.5 billion anaemic people worldwide in 1990, 1.8 billion in 2019, and 1.92 billion in 2021.

Symptoms

Signs and symptoms can vary depending on the cause and severity of the anaemia, and may include the following:

  • Fatigue, tired.
  • Unexplained weakness.
  • Pale or yellowish skin.
  • Irregular heartbeats.
  • Shortness of breath.
  • Dizziness or light-headedness.
  • Chest pain.
  • Cold hands and feet.
  • Headaches.

Causes

  • Congenital (present at birth).
  • Hereditary.
  • Acquired.
  • The body does not make enough RBCs.
  • Bleeding – lose RBCs more quickly than they can be replaced.
  • The body destroys RBCs.

Risk factors

The following can increase the risk of anaemia:

  • A diet low in iron, vitamin B-12, folate and copper. 
  • Having an intestinal disorder (e.g., Crohn’s or celiac disease) affects nutrient absorption. 
  • Menstruating women have a higher risk of iron deficiency and a loss of RBCs.
  • Pregnant women and women not taking folic acid and iron supplementation.
  • Chronic conditions such as cancer can lead to a shortage of RBCs.
  • Slow blood loss within the body (e.g., from an ulcer) can deplete the body of iron.
  • Family history.
  • Infections, blood diseases and autoimmune disorders.
  • People aged over 65 years.

Types of anaemia

Anaemia can be temporary or long term; mild or severe.

Iron deficiency anaemia – this common type of anaemia is when the body lacks appropriate levels or iron. Iron is needed to produce sufficient levels of haemoglobin to carry oxygen around the body. Symptoms include tiredness and shortness of breath.

Vitamin deficiency anaemia – the body lacks healthy RBCs caused by a reduction in vitamin B-12 and folate. Without sufficient levels of these nutrients, the body produces RBCs which are too large and do not work properly; therefore, reducing their ability to carry oxygen. Symptoms include fatigue, SOB and dizziness.

Aplastic anaemia – when the body stops producing enough new blood cells and can lead to uncontrolled bleeding and an increased risk of infections. This condition is rare and serious and can develop at any age; develop suddenly or over time. In addition to the above symptoms, further signs or symptoms may present – aplastic anaemia can have unexplained or easy bruising; nosebleeds, bleeding gums, and prolonged bleeding from cuts; skin rash; and fever.

Thalassemia – this is an inherited blood disorder which causes the body to have less haemoglobin than normal. Mild thalassemia may not require treatment however, severe forms might involve ongoing blood transfusions. In addition to the above symptoms, other signs or symptoms may appear – facial bone deformities; slow growth; abnormal swelling; and dark urine.

Low haemoglobin and cognitive health

As mentioned above, HGB is an important factor involved in transporting oxygen around the body. Research has shown that there is a link between anaemia and dementia among the elderly, however the mechanisms involved are not well known. Below are the findings from recent studies which showed that low haemoglobin levels and anaemia are associated with lower cognitive health, Dementia and Alzheimer’s disease.

Summary of research findings:

Associations of blood cell indices and anemia with risk of incident dementia, 2023

  • Decreased levels of RBC and HGB are indicative of anaemia, and were associated with higher dementia incidence.
  • Red blood cell distribution width (RDW) was a sign of the assortment of RBCs which was positively related to dementia risk.
  • When the World Health Organization’s criteria for anaemia was applied, individuals with anaemia showed a 56% higher risk of dementia compared to those who were not anaemic.
  • Results also showed that the risk was increased despite the cause of anaemia – deficiencies in nutrients (iron, Vitamin B12 or folate).

The impact of low haemoglobin levels on cognitive brain functions, 2020

  • Hypoxia (or hypoxemia) is a low level of oxygen in the blood and can be caused by anaemia and be a mechanism responsible for dementia.
  • Anaemia leads to a rise in the risk of dementia by 34% and Alzheimer’s disease by 41%.
  • One theory is that low HGB could cause chronic hypoxia of brain cells which cause inflammation of neurons which can cause a decline in brain functions. The brain reacts to the anaemia by dilating the blood vessels (vasodilation) which causes the brain to increase blood flow to try to compensate for the reduction in HGB. However, this adjustment fails and blood flow to the cerebral cortex becomes insufficient, leading to neurological deficiency.
  • Another theory is associated with erythropoietin (EPO - hormone which stimulates RBC production in response to hypoxia) receptors in the brain. EPO acts as neuroprotective against hypoxia, therefore low EPO levels may induce the risk of neuronal damage and cognitive decline.

Further clinical studies are recommended to determine the exact association between low HGB levels and decreased cognitive brain functions. However, these studies show the possible link with anaemia and dementia which demonstes the necessity for research into establishing preventative screening tests.

Haemoglobin levels and pregnancy

Anaemia during pregnancy is commonly due to iron or folate deficiency. However, another mechanism during pregnancy also plays a role. At the beginning of pregnancy, plasma volume and haemoglobin levels increase, with the plasma levels rising disproportionately at about the sixth week. This affects haemoglobin levels, causing them to decline, producing anaemia.

Anaemia during pregnancy is correlated to an increased risk of caesarean section, maternal mortality and adverse consequences such as preterm birth, small for gestational age (SGA), and perinatal and neonatal mortality. Research suggests a link between maternal haemoglobin levels and these outcomes.

At the beginning of pregnancy, plasma volume and haemoglobin levels increase, however at about the sixth week point, the plasma levels rise disproportionately. This affects haemoglobin levels, causing them to decline, producing anaemia.

During pregnancy, a haemoglobin level of <110g/L in the first trimester and <105 or 110g/L in the second and third trimester is classed has having anaemia. The WHO also base anaemia on a haemoglobin threshold of <110g/L. The CDC and WHO have established specific cutoffs for maternal anaemia; <110g/L for first and third trimester and 105g/L for the second trimester. Maternal mortality was twice as high in women with severe anaemia compared to those without. Severe anaemia is defined as haemoglobin concentrations less than 70g/L.

Hypoxia (inadequate oxygen supply to organs and tissues) can be the result of being anaemic. Studies believe hypoxia of the placenta may be associated to pregnancy complications such as pre-eclampsia, intrauterine growth restriction and SGA. The theory is that both anaemia and elevated haemoglobin scores throughout pregnancy may lead to a suboptimal oxygen supply and reduced nutrients being delivered to the placenta and foetus. Therefore, haemoglobin cutoff levels may be associated with a decreased risk of adverse maternal and neonatal outcomes.

References

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