Anthropometric Surveys

When energy intake is insufficient to meet requirements, energy is derived by metabolizing fat and lean tissues, mainly muscle. Children first stop gaining height/length and then lose weight, whereas adults lose weight. Weight loss is more rapid in children

Figure 3 Dietary energy supply (DES), 1994-1996. (Reproduced with permission from the Food and Agriculture Organization (2000) Undernourishment around the world. Counting the hungry: Latest estimates. In: The State of Food Insecurity in the World. Rome: FAO.)

than in adults because of their higher energy requirements per kilogram body weight, mainly due to a different body composition. Population-level measurements of body weight and height/length in children indirectly assess the adequacy of food intake on the assumption that a low average body weight and height/length compared with a growth reference reflects an inadequate diet. WHO recommends that the following be used to compare undernutrition in children in different areas of the world:

• Underweight is defined as the proportion of children whose weight in relation to their age is below —2 standard deviations (—2 z scores) of the median of the National Center for Health Statistics (NCHS) reference.

• Wasting is the proportion of children whose weight in relation to their height is below —2 z scores of the median of the NCHS reference.

• Stunting is the proportion of children whose height in relation to their age is below —2 z scores of the median of the NCHS reference.

The previous calculations underestimate the true prevalence of undernutrition because a child can be below his or her optimal weight or height/length yet remain above the —2 z score cutoff point. Wasting is often described as acute malnutrition because it reflects relatively recent weight loss, and stunting is described as chronic malnutrition. Growth retardation is often described as protein-energy malnutrition, which is a misnomer because there is increasing evidence that other nutritional deficiencies besides protein-energy, such as zinc, can lead to growth faltering. Severe undernutrition is defined by a weight in relation to height below —3 z scores of the NCHS reference (marasmus) and/or by the presence of nutritional edema (kwashiorkor or marasmus kwashiorkor), and it is associated with a high risk of dying. WHO and UNICEF maintain a global database on the prevalence of undernutrition among children. Stunting is more prevalent than underweight (Table 1) and is often used to monitor long-term trends in undernutrition.

In emergency situations, rapid assessment surveys are often carried out using the mid-upper arm circumference as a proximate indicator of nutritional status in children and, increasingly, adults. This approach is less reliable than methods based on

Table 1 Prevalence of undernutrition by region

UNICEF region

Under-5

Wasting

Underweight

Stunting

population, 2000a

prevalence (%)

prevalence (%)

prevalence (%)

Moderate and

Severe

Moderate and

Severe

Moderate

Severe

severe

severe

and severe

Sub-Saharan Africa

106394

10

3

30

9

41

20

Middle East and

44 478

7

2

15

4

23

9

North Africa

South Asia

166566

15

2

46

16

45

22

East Asia and Pacific

159454

4

17

21

Latin America and

54 809

2

0

8

1

16

5

Caribbean

CEE/CIS and Baltic

30020

4

1

7

2

16

7

states

Industrialized

50655

countries

Developing countries

546471

9

2

28

10

32

17

Least developed

110458

10

2

37

11

43

20

countries

Sources: http://childinfo.org/eddb/malnutrition/database1.htm (underweight), http://childinfo.org/eddb/malnutrition/database2.htm (stunting), and http://childinfo.org/eddb/malnutrition/database3.htm (wasting).

aIn thousands.

Sources: http://childinfo.org/eddb/malnutrition/database1.htm (underweight), http://childinfo.org/eddb/malnutrition/database2.htm (stunting), and http://childinfo.org/eddb/malnutrition/database3.htm (wasting).

weight and height for epidemiological assessment of undernutrition. Measures of mid-upper arm circumference, however, are useful for screening to quickly identify the severely undernourished, especially children, who are at high risk of dying and need urgent case management.

Anthropometry is also used to assess undernutri-tion in adults, usually as the body mass index (weight/ height2). A body mass index of less than 18.5 defines chronic energy deficiency, and that less than 16.0 defines severe chronic energy deficiency. A global database on maternal nutrition is not available.

Anthropometric surveys do not give information on the causes (dietary, infectious, or other) of the weight and height deficits they measure. Genetic factors are unlikely to determine child growth at a population level because growth is very similar among well-off children from different countries. Breast-feeding patterns, however, may affect growth patterns, and WHO is developing new growth references based on a longitudinal study of infants from diverse geographic sites who are exclusively or predominantly breast fed for at least 4 months with continued breast feeding throughout the first year and on a cross-sectional study of infants and young children age 18-71 months.

Approximately 55% of all child deaths in developing countries are associated with undernutrition (Figure 4), of which at least three-fourths are related to moderate or mild undernutrition rather than severe undernutrition. Some nutritional deficiencies, such as vitamin A, can result in higher mortality without a clear effect on growth. Hence, studies examining the association between undernutrition and mortality, using anthropometry as proxy for undernutrition, are likely to underestimate the strength of this relationship.

Figure 4 Association between malnutrition assessed by anthropometry and cause-specific mortality in children younger than 5years of age. (Reproduced with permission from the WHO Department of Child and Adolescent Health and Development (2002) Available at www.who.int/child-adolescent-health/ 0VERVIEW/CHILD_HEALTH/map_02_world.jpg. Sources: for cause-specific mortality, EIP/WHO; for malnutrition, Pelletier DL, Frongillo EA Jr, and Habicht JP (1993) Epidemiological evidence for a potentiating effect of malnutrition on child mortality. American Journal of Public Health 83: 1130-1133.)

Figure 4 Association between malnutrition assessed by anthropometry and cause-specific mortality in children younger than 5years of age. (Reproduced with permission from the WHO Department of Child and Adolescent Health and Development (2002) Available at www.who.int/child-adolescent-health/ 0VERVIEW/CHILD_HEALTH/map_02_world.jpg. Sources: for cause-specific mortality, EIP/WHO; for malnutrition, Pelletier DL, Frongillo EA Jr, and Habicht JP (1993) Epidemiological evidence for a potentiating effect of malnutrition on child mortality. American Journal of Public Health 83: 1130-1133.)

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