What are the causes of anemia? Can anemia be prevented?

For most people, the word "anemia" is not unfamiliar. Many people think that anemia is just a minor problem and generally will not be checked or treated unless they feel uncomfortable. But in fact, anemia may seem like a minor matter, but if it is not intervened in time and allowed to develop, it will often cause a series of serious problems. In addition, certain diseases often have symptoms of anemia. If the diagnosis and treatment of anemia is neglected, the best time to treat the primary disease may even be missed. So, how much do you know about anemia?

1. Anemia is a global problem

According to data previously released by the World Health Organization (WHO), the number of people suffering from anemia worldwide has exceeded 2 billion, accounting for about 37% of the world's population. In China, the average prevalence of anemia among people aged 6 and above is about 9.7%. Although the incidence of anemia is high worldwide, the highest incidence of anemia is among pregnant women, non-pregnant women of childbearing age, and children under 5 years old.

Although the number of people suffering from anemia is large, the number of people who can receive systematic examination, diagnosis and treatment in the early stage of anemia is relatively small. Even among patients who have developed severe anemia, only half of them receive treatment. Anemia not only affects individual functions, but is also closely related to the occurrence, development and prognosis of many diseases. Therefore, early examination, early diagnosis and early treatment of anemia are crucial.

2. What is anemia ?

Anemia refers to a decrease in the volume of red blood cells in the human body's peripheral blood. The red blood cells in the peripheral blood have the function of transporting oxygen and can deliver oxygen to various tissues and organs of the human body. The decrease in red blood cells will cause a decrease in the oxygen-carrying capacity of the corresponding components of the blood, which will lead to insufficient oxygen supply and hypoxia in human tissues and organs to varying degrees. In other words, anemia refers to a decrease in the volume of peripheral red blood cells, including a series of lesions caused by a decrease in hemoglobin content, a decrease in red blood cell count, and a decrease in hematocrit.

Criteria for determining anemia

Hemoglobin concentration is an important indicator for determining the severity of anemia. According to different population classifications, the normal range of hemoglobin concentration is generally:

Adult males : 120-160 g/L

Adult women : 110-150 g/L

●Newborn : 170g/L.

According to the anemia classification standards developed by the National Cancer Institute (NCI) of the United States and the hematology profession in my country: at sea level, anemia is considered when the hemoglobin concentration of adult males is less than 120g/L, the hemoglobin concentration of adult females is less than 110g/L, and the hemoglobin concentration of pregnant women is less than 100g/L.

According to the standards of the National Cancer Institute (NCI), anemia can be divided into four levels according to the level of hemoglobin concentration: mild anemia, moderate anemia, severe anemia and very severe anemia.

● Mild anemia : Hemoglobin concentration ≥ 90 g/L, but still lower than normal;

●Moderate anemia : hemoglobin concentration is 60-89 g/L;

●Severe anemia : hemoglobin concentration is 30-59 g/L;

●Extremely severe anemia : hemoglobin concentration <30g/L.

3. What are the causes of anemia ?

The causes of anemia mainly include three categories, namely, decreased or insufficient red blood cell production, excessive red blood cell destruction and blood loss.

1. Reduced or insufficient production of red blood cells

Lack of hematopoietic raw materials

Insufficient sources of hematopoietic raw materials, as well as obstacles in the absorption, transport and utilization of hematopoietic raw materials, can lead to reduced or insufficient red blood cell production, thus causing anemia. For example, insufficient iron intake (dietary iron deficiency, absorption disorders), excessive iron loss (chronic blood loss) and increased iron demand (pregnancy, infancy) can cause iron deficiency, leading to iron deficiency anemia; the lack of folic acid and/or vitamin B12 can cause obstacles to DNA synthesis in cells, leading to megaloblastic anemia.

Hematopoietic cell abnormalities

The reduction or abnormal quality of bone marrow erythroid hematopoietic stem cells and hematopoietic progenitor cells will lead to ineffective bone marrow hematopoiesis. Bone metastasis of certain malignant tumors will lead to a decrease in effective hematopoietic cells in the bone marrow. In addition, radiotherapy and chemotherapy are the most commonly used treatments for cancer patients. However, chemotherapy and radiotherapy usually cause complications such as bone marrow suppression, that is, damage to hematopoietic cells leads to abnormal hematopoiesis.

Abnormal hematopoietic microenvironment and regulatory factors

The differentiation, development, proliferation and maturation of hematopoietic stem cells depend on the hematopoietic microenvironment. Abnormalities in the hematopoietic microenvironment are likely to lead to anemia. Abnormalities in various hematopoietic regulatory factors such as erythropoietin, tumor necrosis factor, interferon and other hematopoietic regulatory factors can also lead to anemia.

2. Excessive destruction of red blood cells

Among the many types of anemia, there is one called "hemolytic anemia", which is characterized by a shortened life span of red blood cells. Anemia is caused by increased destruction of red blood cells due to defects in the red blood cells themselves or external factors, which leads to a decrease in red blood cells.

3. Blood loss

Anemia caused by blood loss is also called hemorrhagic anemia, which includes acute massive blood loss in a short period of time and chronic blood loss.

●Acute blood loss : due to trauma or disease, the blood vessels rupture, or due to coagulation disorders, untimely hemostasis, etc., the body loses a large amount of blood in a short period of time, thus causing ischemic anemia. It is mainly seen in trauma, rupture of esophageal or gastric veins, gastrointestinal bleeding, ectopic pregnancy or heavy bleeding during childbirth, rupture of internal organs, etc.

●Chronic blood loss : Chronic gastrointestinal diseases, such as peptic ulcer (gastroduodenal ulcer), hemorrhoids, parasitic infection, menorrhagia, etc., can cause long-term chronic blood loss and induce anemia.

4. What are the symptoms of anemia ?

Anemia is not an independent disease, it can cause multiple different manifestations in multiple systems. The severity of the symptoms caused by anemia is related to the degree of anemia, the speed of anemia progression, and the body's ability to regulate and compensate for anemia. In the early stages of anemia, patients often experience symptoms of dizziness, weakness, fatigue, and pale skin and mucous membranes. Typical symptoms of anemia include the following:

Skin and mucous membrane symptoms

Pale skin and mucous membranes are the most common symptom of anemia. Anemic patients will have pale skin and mucous membranes, eyelid conjunctiva, oral mucosa and nail beds. In addition, they may also have dry skin, lack of luster, and dry hair. Some patients may also have typical signs such as spoon-shaped fingers, beef tongue, and mirror tongue.

Respiratory and circulatory system symptoms

Anemia patients often experience symptoms such as increased breathing and heart rate, chest tightness and palpitations. For patients with mild anemia, there are generally no obvious symptoms, and symptoms such as palpitations and shortness of breath only occur after activities. Patients with severe anemia will experience obvious chest tightness, shortness of breath and dyspnea even in a quiet state. If the anemia state lasts for a long time, it can lead to increased cardiac output, enlarged heart or chronic heart failure, which can cause anemic heart disease.

Neuromuscular symptoms

The main effect of anemia on the nervous system is that the body is in a state of hypoxia, which can cause symptoms such as headache, dizziness, tinnitus, syncope, memory loss and poor concentration. The main effect on muscles is muscle weakness, fatigue and other symptoms of tissue hypoxia.

Digestive symptoms

Anemia patients often experience symptoms such as loss of appetite, nausea, abdominal distension, constipation and diarrhea. If it is megaloblastic anemia or pernicious anemia, it may also cause glossitis, tongue atrophy and other symptoms. If anemia is caused by gastrointestinal bleeding, patients often experience black stools (suet-like stools).

Urinary , reproductive , and endocrine system symptoms

Anemia patients will experience polyuria, proteinuria (foamy urine) and other symptoms. Long-term anemia will also affect the secretion of testosterone in men, weakening male characteristics; for women, it will also affect the secretion of female hormones and cause menstrual abnormalities, which may cause menstrual cycle disorders, decreased or increased menstrual volume, or even amenorrhea. Patients with severe anemia may also experience symptoms such as decreased libido. Long-term anemia will also affect the function of the body's endocrine glands and the secretion of erythropoietin.

In addition, long-term anemia will also affect the function of the thyroid gland, adrenal glands, etc. It will also cause the patient's immune function to be impaired, causing a decrease in immunity and susceptibility to infection.

5. Classification of Anemia

According to the cytometric classification of anemia, anemia can be divided into macrocytic anemia, normocytic anemia and microcytic hypochromic anemia. Among the many types of anemia, iron deficiency anemia is the most common.

●Macrocytic anemia : common in megaloblastic anemia, hemolytic anemia with reticulocytosis, myelodysplastic syndrome, liver disease, etc.

●Normal cell anemia : common in aplastic anemia, hemolytic anemia, acute hemorrhagic anemia, etc.

●Microcytic hypochromic anemia : common in iron deficiency anemia, thalassemia, sideroblastic anemia and anemia of chronic disease.

Iron deficiency anemia

The World Health Organization states that 30% of the world's population may suffer from anemia, and most of them suffer from iron deficiency anemia.

Due to the lack of iron in the body, hemoglobin synthesis is reduced, with the main characteristics of microcytic hypochromic anemia, decreased serum ferritin and effective iron treatment. Iron deficiency is the main cause of anemia in children and adults. Patients with iron deficiency anemia are prone to angular cheilitis, glossitis, chronic atrophic gastritis, koilonychia and other manifestations. Some patients also have special symptoms such as pica and dysphagia.

Among anemia patients worldwide, about 43% are children aged 0-5 years old, which seriously affects children's growth and development, leads to psychological and behavioral abnormalities, and even affects children's intellectual development. Pregnant women are also a high-risk group for anemia. The prevalence of iron deficiency anemia in pregnant women in my country is about 20%. Existing data show that the prevalence of iron deficiency anemia in adolescents in my country is about 30%, which is related to dietary structure, living environment and Helicobacter pylori infection. A survey conducted by the China Children, Pregnant Women and Women of Childbearing Age Epidemiological Survey Collaborative Group showed that the prevalence of iron deficiency anemia in women of childbearing age in my country is about 15%.

Megaloblastic anemia

Megaloblastic anemia, also known as pernicious anemia, is not common in China and is caused by a lack of folic acid and/or vitamin B12. Patients often experience symptoms such as loss of appetite, abdominal distension, constipation, glossitis, numbness of the hands and feet, and mood changes.

Hemolytic anemia

Due to the influence of infection, heredity, immune dysfunction and other factors, a large number of red blood cells are destroyed directly or indirectly, and the rate of red blood cell destruction is higher than the rate of its generation, which can cause hemolytic anemia. Patients often experience symptoms such as fatigue, inattention, pale complexion and jaundice (yellowing of the skin and eyes), and darker urine color such as strong tea or soy sauce.

Aplastic anemia

Aplastic anemia is a group of clinical syndromes caused by a decrease or failure of bone marrow hematopoietic function due to various reasons, leading to pancytopenia. It often presents with symptoms such as severe anemia, bleeding and infection. Severe and extremely severe aplastic anemia can cause death due to severe infection or intracranial hemorrhage. In recent years, scholars at home and abroad generally believe that aplastic anemia is a type of autoimmune disease with abnormal immune function. Depending on the cause, aplastic anemia is divided into congenital aplastic anemia and acquired aplastic anemia. Congenital aplastic anemia is related to genetic factors, while acquired aplastic anemia is mainly related to direct damage from immune factors and physical, chemical, biological, and environmental factors.

6. How to treat anemia ?

Anemia is a clinical syndrome. If anemia occurs, the cause must be identified first, and then actively treated. Treatments for anemia include medication, surgery, and so on.

1. Drug treatment

Iron therapy

The purpose of iron supplementation is to provide sufficient raw materials for hematopoiesis, and it is mainly used to treat iron deficiency anemia. Commonly used iron supplements include ferrous sulfate, iron dextran, ferrous gluconate, and sorbitol iron. Pregnant women with mild or moderate anemia can take ferrous sulfate orally to supplement iron, and those with severe anemia can take intravenous iron supplements.

Folic acid , vitamin B12 treatment

Megaloblastic anemia is related to the deficiency of folic acid and vitamin B12. Supplementation of these two vitamins can treat megaloblastic anemia caused by folic acid and vitamin B12 deficiency.

Hormone therapy

For autoimmune hemolytic anemia, hormone therapy is often used to suppress the patient's own immune response. Commonly used hormone therapy drugs include: dexamethasone, methylprednisolone and prednisone.

Cyclosporine A combined with androgen therapy

Androgens have a good therapeutic effect on chronic aplastic anemia. Cyclosporine A combined with androgens can inhibit the patient's autoimmune response and promote hematopoiesis. Commonly used androgens in clinical practice include stanozolol, testosterone propionate, danazol, etc.

Cytokine therapy

Cytokines can stimulate the proliferation and differentiation of hematopoietic cells and improve hematopoietic function. Commonly used cytokines include erythropoietin (for renal anemia), granulocyte-macrophage colony stimulating factor, etc.

2. Surgical treatment

For patients with hereditary spherocytosis, hypersplenism, and autoimmune hemolytic anemia that is ineffective with medical treatment, splenectomy can be performed. Splenectomy can reduce the damage of the spleen to red blood cells and achieve the purpose of treating hemolytic anemia. Hematopoietic stem cell transplantation can restore the patient's hematopoietic function and is suitable for acute aplastic anemia, bone marrow hematopoietic failure, severe hereditary anemia, and malignant diseases of the blood system.

3. Other treatments

For the treatment of anemia, comprehensive treatment methods such as blood transfusion therapy, traditional Chinese medicine treatment and gene therapy are also used clinically.

7. Anemia is the most common symptom associated with tumors

Malignant tumors pose a serious threat to public health worldwide, and are also a factor contributing to the high mortality rate in my country. Tumor-related anemia often accompanies malignant tumors. The incidence of anemia is high in patients with malignant tumors, especially in patients with lymphoma, multiple myeloma, lung cancer, gynecological tumors, and reproductive system tumors, where the incidence is around 60%.

On the one hand, the first symptom of some malignant tumors is anemia. Many patients will ignore the impact of the primary malignant tumor due to the symptoms of anemia, and it is easy to miss the best time to treat the tumor due to delaying the disease. On the other hand, tumor-related anemia often causes a series of clinical symptoms, resulting in a decrease in the patient's quality of life, and also leads to a decrease in tolerance to tumor treatment and a decrease in the sensitivity of tumor tissue to treatment methods such as radiotherapy and chemotherapy. Tumor-related anemia not only reduces the patient's quality of life, it is also an adverse factor affecting the prognosis of tumor patients and will reduce the patient's survival time.

8. Can anemia be prevented ?

Except for anemia related to genetic factors, most anemia can be prevented. To prevent anemia, you should do the following:

1. Develop a healthy lifestyle

Quit smoking and drinking, and avoid long-term drinking of coffee and strong tea. Arrange your diet reasonably, pay attention to balanced nutrition, and ensure a balanced distribution of protein, carbohydrates, and fat intake. Increase the intake of foods rich in trace elements. For children, pregnant women, and people of childbearing age, pay attention to increasing the intake of animal foods and foods rich in vitamin C to promote iron absorption.

2. Preventive iron supplementation

As mentioned above, although the incidence of anemia is high worldwide, iron deficiency anemia is the most common. Currently, many countries recommend that pregnant women should take preventive iron supplements to prevent iron deficiency and iron deficiency anemia during pregnancy. However, iron supplementation should be carried out under the guidance of a professional doctor, and iron supplementation should not be done without authorization, so as to avoid excessive iron inducing pregnancy complications such as heart disease.

Because premature and low-birth-weight infants have insufficient iron reserves, they are more likely to suffer from iron deficiency than full-term infants. They should take preventive iron supplements. For children who have already developed anemia, they should take iron supplements under the guidance of a professional doctor.

When taking iron supplements, be careful to avoid taking calcium supplements, because calcium and iron will compete with each other for absorption. Therefore, if both are used at the same time, they will competitively inhibit the absorption of iron in the body. Therefore, high-calcium foods should not be eaten with iron supplements or iron-rich foods, and should be eaten separately. In addition, it is best to take iron supplements after meals to avoid aggravating gastrointestinal reactions and affecting the absorption of iron supplements.

3. Actively treat the primary disease

Suffering from certain common diseases, such as gastric and duodenal ulcers, hemorrhoids, infections, rheumatic diseases and other diseases, can cause or aggravate anemia. Therefore, if the above problems occur, active treatment and intervention must be carried out.

4. Improve the stimulation of adverse environmental factors

Avoid long-term exposure to chemicals (herbicides, hair dyes, etc.), high-energy rays (X-rays, etc.) and certain viruses to prevent anemia and related complications.

5. Carry out disease inspection and screening

For anemia related to genetics, attention should be paid to early disease screening. Taking thalassemia as an example, there is currently no effective and reliable treatment for thalassemia. The provinces south of the Yangtze River in my country, especially Guangdong, Guangxi, Hainan, Sichuan, Yunnan, Guizhou and other regions are high-incidence areas of thalassemia. In some of these high-incidence areas, the thalassemia gene carrier rate in the population exceeds 10%. Therefore, in areas where thalassemia is highly prevalent, every woman of childbearing age, pregnant woman and her spouse should undergo pre-pregnancy examinations and prenatal screening. For high-risk groups found through examinations and screening, prenatal diagnosis and pre-implantation diagnosis should be performed to prevent the birth of children with severe thalassemia, which is currently a relatively effective preventive measure.

6. Supplement iron-rich foods appropriately

Some foods have high iron content, so you can supplement them appropriately at ordinary times. Foods with high iron content include: animal liver, lamb liver or chicken liver, which are all foods with very high iron content. However, animal liver has a high fat content, so you should pay attention to controlling the amount you consume. When choosing meat, you should pay attention to the fact that red meat contains more iron, but red meat has a relatively high fat content. You should pay attention to choosing lean meat parts, such as beef and lamb. Pork also has a relatively high iron content, so you can also choose it appropriately. Seafood foods such as fish and shrimp have a lower iron content. In addition, blood products such as blood tofu, duck blood, soybeans and their soy products also have high iron content, so you can choose according to your preferences.

Although anemia seems to be just a simple symptom, its occurrence is not independent and is often associated with multiple diseases. Therefore, if you experience symptoms such as fatigue, dizziness, and pale lips, you must go to the hospital for examination in time. Early detection, early diagnosis, and early treatment are the key.

Author: Zhang Jing

Scientific review: Leng Yun, deputy chief physician of the Department of Hematology, Beijing Chaoyang Hospital