Anaemia

What does this indicator tell us?

The indicator anaemia has a wide variety of causes. Iron deficiency is considered to be the most common cause of anaemia; other causes include acute and chronic infections that result in inflammation and blood loss; deficiencies of other vitamins and minerals, especially folate, vitamin B₁₂ and vitamin A; and genetically inherited traits, such as thalassaemia. Other conditions (e.g. malaria and other infections, genetic disorders, and cancer) can also play a role in anaemia. The terms “iron-deficiency anaemia” and “anaemia” are often used synonymously; also, the prevalence of anaemia has often been used as a proxy for iron-deficiency anaemia, although the degree of overlap between the two varies considerably from one population to another, according to gender and age.

Anaemia prevalence among pregnant and non-pregnant women are included as primary outcome indicators in the core set of indicators for the Global nutrition monitoring framework. These indicators are used to monitor progress towards achieving Global Nutrition Target 2, which is a 50% reduction in anaemia among women of reproductive age by 2025. Anaemia in women of reproductive age and in children are also included in the WHO Global reference list of 100 core health indicators.

How is this indicator defined?

Anaemia is defined as a haemoglobin concentration below a specified cut-off point; that cut-off point depends on the age, gender, physiological status, smoking habits and altitude at which the population being assessed lives. WHO defines anaemia in children aged under 5 years and pregnant women as a haemoglobin concentration <110 g/L at sea level, and anaemia in non-pregnant women as a haemoglobin concentration <120 g/L.

Tests to measure haemoglobin levels are easy to administer. A few drops of blood obtained by a finger-stick can be used to assess haemoglobin concentrations in the field using a portable haemoglobinometer. The test could be easily integrated into regular health or prenatal visits or household surveys, to capture women of reproductive age, although the cost of the equipment and regular calibration needs to be taken into account.

What are the consequences and implications?

Anaemia is associated with increased risks for maternal and child mortality. Iron-deficiency anaemia reduces the work capacity of individuals and entire populations, with serious consequences for the economy and national development. In addition, the negative consequences of iron-deficiency anaemia on the cognitive and physical development of children and on physical performance – particularly the work productivity of adults – are major concerns. Anaemia is a global problem affecting all countries. Resource-poor areas are often more heavily affected because of the prevalence of infectious diseases. Malaria, HIV/AIDS, hookworm infestation, schistosomiasis and other infections such as tuberculosis contribute to the high prevalence of anaemia in some areas.

The main risk factors for iron-deficiency anaemia include a low dietary intake of iron or poor absorption of iron from diets rich in phytates or phenolic compounds. Population groups with greater iron requirements, such as growing children and pregnant women, are particularly at risk. Overall, the most vulnerable, poorest and least educated groups are disproportionately affected by iron-deficiency anaemia.

Cut-off values for public health significance

Source: WHO (2008).

Sources of data

WHO. Global Health Observatory (GHO) data repository.

Prevalence of anaemia in pregnant women. Estimates by country. (http://apps.who.int/gho/data/view.main.ANAEMIAWOMENPWv).

Prevalence of anaemia in non-pregnant women. Estimates by country (http://apps.who.int/gho/data/view.main.ANAEMIAWOMENNPWv).

Further reading

Stevens GA, Finucane MM, De-Regil LM, Paciorek CJ, Flaxman SR, Branca F et al. Global, regional, and national trends in haemoglobin concentration and prevalence of total and severe anaemia in children and pregnant and non-pregnant women for 1995–2011: a systematic analysis of population-representative data. Lancet Global Health. 2013;1:e16–25.

WHO. Global nutrition targets 2025: anaemia policy brief. Geneva: World Health Organization; 2014 (http://who.int/nutrition/publications/globaltargets2025_policybrief_anaemia/en/).

WHO. Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity. Vitamin and Mineral Nutrition Information System. WHO/NMH/NHD/MNM/11.1. Geneva: World Health Organization; 2011 (http://www.who.int/vmnis/indicators/haemoglobin.pdf).

WHO, UNICEF. Global nutrition monitoring framework: operational guidance for tracking progress in meeting targets for 2025. Geneva: World Health Organization; 2017 (http://www.who.int/nutrition/publications/operational-guidance-GNMF-indicators/en/).

WHO. Global reference list of 100 core health indicators (plus health-related SDGs). Geneva: World Health Organization; 2018 (https://www.who.int/healthinfo/indicators/2018/en/).

Internet resources

WHO. Vitamin and Mineral Nutrition Information System (VMNIS).  (http://www.who.int/vmnis/en/).

WHO. Anaemia/iron deficiency list of publications. (http://www.who.int/nutrition/publications/micronutrients/anaemia_iron_deficiency/en/index.html).

WHO. e-Library of Evidence for Nutrition Actions (eLENA). Health conditions. Anaemia (http://www.who.int/elena/health_condition/en/#anaemia).

WHO. e-Library of Evidence for Nutrition Actions (eLENA). Interventions by global target (http://www.who.int/elena/global-targets/en):

Target 2: 50% reduction of anaemia in women of reproductive age (http://www.who.int/elena/global-targets/en/#anaemia).

Anaemia

What does this indicator tell us?

The indicator anaemia has a wide variety of causes. Iron deficiency is considered to be the most common cause of anaemia; other causes include acute and chronic infections that result in inflammation and blood loss; deficiencies of other vitamins and minerals, especially folate, vitamin B₁₂ and vitamin A; and genetically inherited traits, such as thalassaemia. Other conditions (e.g. malaria and other infections, genetic disorders, and cancer) can also play a role in anaemia. The terms “iron-deficiency anaemia” and “anaemia” are often used synonymously; also, the prevalence of anaemia has often been used as a proxy for iron-deficiency anaemia, although the degree of overlap between the two varies considerably from one population to another, according to gender and age.

Anaemia prevalence among pregnant and non-pregnant women are included as primary outcome indicators in the core set of indicators for the Global nutrition monitoring framework. These indicators are used to monitor progress towards achieving Global Nutrition Target 2, which is a 50% reduction in anaemia among women of reproductive age by 2025. Anaemia in women of reproductive age and in children are also included in the WHO Global reference list of 100 core health indicators.

How is this indicator defined?

Anaemia is defined as a haemoglobin concentration below a specified cut-off point; that cut-off point depends on the age, gender, physiological status, smoking habits and altitude at which the population being assessed lives. WHO defines anaemia in children aged under 5 years and pregnant women as a haemoglobin concentration <110 g/L at sea level, and anaemia in non-pregnant women as a haemoglobin concentration <120 g/L.

Tests to measure haemoglobin levels are easy to administer. A few drops of blood obtained by a finger-stick can be used to assess haemoglobin concentrations in the field using a portable haemoglobinometer. The test could be easily integrated into regular health or prenatal visits or household surveys, to capture women of reproductive age, although the cost of the equipment and regular calibration needs to be taken into account.

What are the consequences and implications?

Anaemia is associated with increased risks for maternal and child mortality. Iron-deficiency anaemia reduces the work capacity of individuals and entire populations, with serious consequences for the economy and national development. In addition, the negative consequences of iron-deficiency anaemia on the cognitive and physical development of children and on physical performance – particularly the work productivity of adults – are major concerns. Anaemia is a global problem affecting all countries. Resource-poor areas are often more heavily affected because of the prevalence of infectious diseases. Malaria, HIV/AIDS, hookworm infestation, schistosomiasis and other infections such as tuberculosis contribute to the high prevalence of anaemia in some areas.

The main risk factors for iron-deficiency anaemia include a low dietary intake of iron or poor absorption of iron from diets rich in phytates or phenolic compounds. Population groups with greater iron requirements, such as growing children and pregnant women, are particularly at risk. Overall, the most vulnerable, poorest and least educated groups are disproportionately affected by iron-deficiency anaemia.

Cut-off values for public health significance

Source: WHO (2008).

Sources of data

WHO. Global Health Observatory (GHO) data repository.

Prevalence of anaemia in pregnant women. Estimates by country. (http://apps.who.int/gho/data/view.main.ANAEMIAWOMENPWv).

Prevalence of anaemia in non-pregnant women. Estimates by country (http://apps.who.int/gho/data/view.main.ANAEMIAWOMENNPWv).

Further reading

Stevens GA, Finucane MM, De-Regil LM, Paciorek CJ, Flaxman SR, Branca F et al. Global, regional, and national trends in haemoglobin concentration and prevalence of total and severe anaemia in children and pregnant and non-pregnant women for 1995–2011: a systematic analysis of population-representative data. Lancet Global Health. 2013;1:e16–25.

WHO. Global nutrition targets 2025: anaemia policy brief. Geneva: World Health Organization; 2014 (http://who.int/nutrition/publications/globaltargets2025_policybrief_anaemia/en/).

WHO. Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity. Vitamin and Mineral Nutrition Information System. WHO/NMH/NHD/MNM/11.1. Geneva: World Health Organization; 2011 (http://www.who.int/vmnis/indicators/haemoglobin.pdf).

WHO, UNICEF. Global nutrition monitoring framework: operational guidance for tracking progress in meeting targets for 2025. Geneva: World Health Organization; 2017 (http://www.who.int/nutrition/publications/operational-guidance-GNMF-indicators/en/).

WHO. Global reference list of 100 core health indicators (plus health-related SDGs). Geneva: World Health Organization; 2018 (https://www.who.int/healthinfo/indicators/2018/en/).

Internet resources

WHO. Vitamin and Mineral Nutrition Information System (VMNIS).  (http://www.who.int/vmnis/en/).

WHO. Anaemia/iron deficiency list of publications. (http://www.who.int/nutrition/publications/micronutrients/anaemia_iron_deficiency/en/index.html).

WHO. e-Library of Evidence for Nutrition Actions (eLENA). Health conditions. Anaemia (http://www.who.int/elena/health_condition/en/#anaemia).

WHO. e-Library of Evidence for Nutrition Actions (eLENA). Interventions by global target (http://www.who.int/elena/global-targets/en):

Target 2: 50% reduction of anaemia in women of reproductive age (http://www.who.int/elena/global-targets/en/#anaemia).

Vitamin A deficiency

What does this indicator tell us?

Vitamin A deficiency results from a dietary intake of vitamin A that is inadequate to satisfy physiological needs. It may be exacerbated by high rates of infection, especially diarrhoea and measles. It is common in developing countries, but rarely seen in developed countries. Vitamin A deficiency is a public health problem in more than half of all countries, especially those in Africa and South-East Asia. The most severe effects of this deficiency are seen in young children and pregnant women in low-income countries.

How is this indicator defined?

Vitamin A deficiency can be defined clinically or subclinically. Xerophthalmia is the clinical spectrum of ocular manifestations of vitamin A deficiency; these range from the milder stages of night blindness and Bitot spots to the potentially blinding stages of corneal xerosis, ulceration and necrosis (keratomalacia). The various stages of xerophthalmia are regarded both as disorders and clinical indicators of vitamin A deficiency. Night blindness (in which it is difficult or impossible to see in relatively low light) is one of the clinical signs of vitamin A deficiency, and is common during pregnancy in developing countries. Retinol is the main circulating form of vitamin A in blood and plasma. Serum retinol levels reflect liver vitamin A stores when they are severely depleted or extremely high; however, between these extremes, plasma or serum retinol is homeostatically controlled and hence may not correlate well with vitamin A intake. Therefore, serum retinol is best used for the assessment of subclinical vitamin A deficiency in a population (not in an individual). Blood concentrations of retinol in plasma or serum are used to assess subclinical vitamin A deficiency. A plasma or serum retinol concentration <0.70 μmol/L indicates subclinical vitamin A deficiency in children and adults, and a concentration of <0.35 µmol/L indicates severe vitamin A deficiency.

What are the consequences and implications?

Night blindness is one of the first signs of vitamin A deficiency. In its more severe forms, vitamin A deficiency contributes to blindness by making the cornea very dry, thus damaging the retina and cornea. An estimated 250 000–500 000 children who are vitamin A-deficient become blind every year, and half of them die within 12 months of losing their sight. Deficiency of vitamin A is associated with significant morbidity and mortality from common childhood infections, and is the world’s leading preventable cause of childhood blindness. Vitamin A deficiency also contributes to maternal mortality and other poor outcomes of pregnancy and lactation. It also diminishes the ability to fight infections. Even mild, subclinical deficiency can be a problem, because it may increase children’s risk for respiratory and diarrhoeal infections, decrease growth rates, slow bone development and decrease the likelihood of survival from serious illness.

Cut-off values for public health significance

Source: WHO (2009).

Source of data

WHO. Vitamin and Mineral Nutrition Information System (VMNIS). Micronutrients database. (http://www.who.int/vmnis/database/en/).

Further reading

Stevens GA, Bennett JE, Hennocq Q, Lu Y, De-Regil LM, Rogers L et al. Trends and mortality effects of vitamin A deficiency in children in 138 low-income and middle-income countries between 1991 and 2013: a pooled analysis of population-based surveys. Lancet Glob Health. 2015;3:e528–36. doi:10.1016/S2214-109X(15)00039-X.

WHO. Global prevalence of vitamin A deficiency in populations at risk 1995–2005. WHO global database on vitamin A deficiency. Geneva: World Health Organization; 2009 (http://whqlibdoc.who.int/publications/2009/9789241598019_eng.pdf).

WHO. Serum retinol concentrations for determining the prevalence of vitamin A deficiency in populations. WHO/NMH/NHD/MNM/11.3. Geneva: World Health Organization; 2011 (http://www.who.int/vmnis/indicators/retinol.pdf).

WHO. Xerophthalmia and night blindness for the assessment of clinical vitamin A deficiency in individuals and populations. WHO/NMH/NHD/EPG/14.4. Geneva: World Health Organization; 2014 (http://apps.who.int/iris/bitstream/10665/133705/1/WHO_NMH_NHD_EPG_14.4_eng.pdf).

Internet resources

WHO. Vitamin A deficiency list of publications. (http://www.who.int/nutrition/publications/micronutrients/vitamin_a_deficiency/en/).

WHO. e-Library of Evidence for Nutrition Actions (eLENA). Nutrients. Vitamin A. (http://www.who.int/elena/nutrient/en/#vitamina).

Vitamin A deficiency

What does this indicator tell us?

Vitamin A deficiency results from a dietary intake of vitamin A that is inadequate to satisfy physiological needs. It may be exacerbated by high rates of infection, especially diarrhoea and measles. It is common in developing countries, but rarely seen in developed countries. Vitamin A deficiency is a public health problem in more than half of all countries, especially those in Africa and South-East Asia. The most severe effects of this deficiency are seen in young children and pregnant women in low-income countries.

How is this indicator defined?

Vitamin A deficiency can be defined clinically or subclinically. Xerophthalmia is the clinical spectrum of ocular manifestations of vitamin A deficiency; these range from the milder stages of night blindness and Bitot spots to the potentially blinding stages of corneal xerosis, ulceration and necrosis (keratomalacia). The various stages of xerophthalmia are regarded both as disorders and clinical indicators of vitamin A deficiency. Night blindness (in which it is difficult or impossible to see in relatively low light) is one of the clinical signs of vitamin A deficiency, and is common during pregnancy in developing countries. Retinol is the main circulating form of vitamin A in blood and plasma. Serum retinol levels reflect liver vitamin A stores when they are severely depleted or extremely high; however, between these extremes, plasma or serum retinol is homeostatically controlled and hence may not correlate well with vitamin A intake. Therefore, serum retinol is best used for the assessment of subclinical vitamin A deficiency in a population (not in an individual). Blood concentrations of retinol in plasma or serum are used to assess subclinical vitamin A deficiency. A plasma or serum retinol concentration <0.70 μmol/L indicates subclinical vitamin A deficiency in children and adults, and a concentration of <0.35 µmol/L indicates severe vitamin A deficiency.

What are the consequences and implications?

Night blindness is one of the first signs of vitamin A deficiency. In its more severe forms, vitamin A deficiency contributes to blindness by making the cornea very dry, thus damaging the retina and cornea. An estimated 250 000–500 000 children who are vitamin A-deficient become blind every year, and half of them die within 12 months of losing their sight. Deficiency of vitamin A is associated with significant morbidity and mortality from common childhood infections, and is the world’s leading preventable cause of childhood blindness. Vitamin A deficiency also contributes to maternal mortality and other poor outcomes of pregnancy and lactation. It also diminishes the ability to fight infections. Even mild, subclinical deficiency can be a problem, because it may increase children’s risk for respiratory and diarrhoeal infections, decrease growth rates, slow bone development and decrease the likelihood of survival from serious illness.

Cut-off values for public health significance

Source: WHO (2009).

Source of data

WHO. Vitamin and Mineral Nutrition Information System (VMNIS). Micronutrients database. (http://www.who.int/vmnis/database/en/).

Further reading

Stevens GA, Bennett JE, Hennocq Q, Lu Y, De-Regil LM, Rogers L et al. Trends and mortality effects of vitamin A deficiency in children in 138 low-income and middle-income countries between 1991 and 2013: a pooled analysis of population-based surveys. Lancet Glob Health. 2015;3:e528–36. doi:10.1016/S2214-109X(15)00039-X.

WHO. Global prevalence of vitamin A deficiency in populations at risk 1995–2005. WHO global database on vitamin A deficiency. Geneva: World Health Organization; 2009 (http://whqlibdoc.who.int/publications/2009/9789241598019_eng.pdf).

WHO. Serum retinol concentrations for determining the prevalence of vitamin A deficiency in populations. WHO/NMH/NHD/MNM/11.3. Geneva: World Health Organization; 2011 (http://www.who.int/vmnis/indicators/retinol.pdf).

WHO. Xerophthalmia and night blindness for the assessment of clinical vitamin A deficiency in individuals and populations. WHO/NMH/NHD/EPG/14.4. Geneva: World Health Organization; 2014 (http://apps.who.int/iris/bitstream/10665/133705/1/WHO_NMH_NHD_EPG_14.4_eng.pdf).

Internet resources

WHO. Vitamin A deficiency list of publications. (http://www.who.int/nutrition/publications/micronutrients/vitamin_a_deficiency/en/).

WHO. e-Library of Evidence for Nutrition Actions (eLENA). Nutrients. Vitamin A. (http://www.who.int/elena/nutrient/en/#vitamina).

Iodine deficiency

What does this indicator tell us?

This indicator allows an assessment of iodine deficiency at the population level. Iodine is an essential trace element that is present in the thyroid hormones, thyroxine and triiodotyronine. It occurs most frequently in areas where there is little iodine in the diet – typically, these are remote inland areas where no marine foods are eaten. Urinary iodine concentration in children aged 6–12 years is included as an additional indicator in the WHO Global reference list of 100 core health indicators.

How is this indicator defined?

Although goitre assessment by palpation or ultrasound may be useful for assessing thyroid function, results are difficult to interpret once salt iodization programmes have started. The median urinary iodine concentration is considered to be the main indicator of iodine status for all age groups, because its measurement is relatively noninvasive, cost-efficient and easy to perform. Since most of the iodine absorbed by the body is excreted in the urine, it is considered to be a sensitive marker of current iodine intake and can reflect recent changes in iodine status. Median urinary iodine concentrations have been most commonly measured in school children aged 6–12 years, because it is easy to access this population.

For school-age children (≥6 years of age), an adequate iodine level is defined as a population median urinary iodine concentration of 100–199 μg/L, whereas a population median of <100 μg/L indicates that the population’s iodine intake is insufficient. When the population median is <20 μg/L, the population is described as having severe iodine deficiency; at 20–49 μg/L, it is described as having moderate iodine deficiency; and at 50–99 μg/L, it is described as having mild iodine deficiency. A population of school-age children should have a median urinary iodine concentration of at least 100 μg/L, with less than 20% of values being <50 μg/L. For pregnant women, the median urinary iodine should be between 150 µg/L and 249 μg/L.

What are the consequences and implications?

Iodine-deficiency disorders, which can start before birth, jeopardize children’s mental health and often their very survival. During the neonatal period, childhood and adolescence, iodine-deficiency disorders can lead to hypothyroidism and hyperthyroidism. Serious iodine deficiency during pregnancy can result in stillbirth, spontaneous abortion and congenital abnormalities such as cretinism – a grave, irreversible form of mental retardation that affects people living in iodine-deficient areas of Africa and Asia. Of even greater significance is the less visible, yet pervasive, mental impairment that reduces intellectual capacity at home, in school and at work.

Cut-off values for public health significance in different target groups

^a Applies to adults, but not to pregnant and lactating women.

^b The term “excessive” means “in excess of the amount required to prevent and control iodine deficiency”.

^c Although lactating women have the same requirement as pregnant women, the median urinary iodine concentration is lower because iodine is excreted in breast milk.

Source: WHO (2013).

Source of data

WHO. Vitamin and Mineral Nutrition Information System (VMNIS). Micronutrients database (http://www.who.int/vmnis/database/en/).

Further reading

WHO. Goitre as a determinant of the prevalence and severity of iodine-deficiency disorders in populations. WHO/NMH/NHD/MNM/14.5. Geneva: World Health Organization; 2014 (http://apps.who.int/iris/bitstream/10665/133706/1/WHO_NMH_NHD_EPG_14.5_eng.pdf).

WHO. Urinary iodine concentrations for determining iodine status deficiency in populations. Vitamin and Mineral Nutrition Information System. Geneva: World Health Organization; 2013 (http://www.who.int/nutrition/vmnis/indicators/urinaryiodine).

Andersson M, Karumbunathan V, Zimmermann MB. Global iodine status in 2011 and trends over the past decade. J Nutr. 2012;142:744–750.

WHO. Global reference list of 100 core health indicators (plus health-related SDGs). Geneva: World Health Organization; 2018 (https://www.who.int/healthinfo/indicators/2018/en/).

Internet resources

WHO. Vitamin and Mineral Nutrition Information System (VMNIS). Urinary iodine concentrations for determining iodine status deficiency in populations (http://www.who.int/vmnis/indicators/urinaryiodine/en/).

WHO. Iodine deficiency list of publications. (http://www.who.int/nutrition/publications/micronutrients/iodine_deficiency/en/).