GOAL AND TARGET ADDRESSED
Goal 1. Eradicate extreme poverty and hunger
Target 1.C: Halve, between 1990 and 2015, the proportion of people who suffer from hunger
DEFINITION AND METHOD OF COMPUTATION
The prevalence of underweight children
under five years of age is defined as the percentage of children aged 0–59 months, whose weights are less than two standard deviations below the median weight for age groups in the international reference population.
The international reference population
is a population against which the growth of children can be compared. The reference population is defined by the World Health Organisation (WHO) Child Growth Standards. The standards are based on more than 8,000 children from Brazil, Ghana, India, Norway, Oman and the United States of America. These children were selected based on their exposure to an optimal environment for proper growth including recommended infant and young child feeding practices, good healthcare, non-smoking mothers, and other factors associated with good health outcomes.
The number of underweight children
is the number of children under five years of age whose weights are less than two standard deviations below the median weight for each age in the international reference population.
Method of computation
The weights of children under five years of age are compared with the weights given in the standard reference population for each age group. The percentage of children underweight is the aggregate of the number of children underweight
divided by the number of children weighed multiplied by 100.
RATIONALE AND INTERPRETATION
Child undernutrition, measured as the prevalence of underweight children, is an important component of the MDGs since it is linked to poverty, low levels of education, and poor access to health services. Undernourishment in children, even moderate, increases their risk of death, inhibits their cognitive development, and affects their health status later in life. Sufficient and good quality nutrition is the cornerstone for development, health and survival of current and succeeding generations. Healthy nutrition is also important for women during pregnancy and lactation, so that their children are born into sound developmental paths, both physically and mentally.
Under-five underweight prevalence is an internationally recognized public health indicator for monitoring nutritional status and health in populations. Child nutritional status is monitored more closely than adult nutritional status.
The numeric value of this indicator refers to the proportion of children under five years of age who are underweight according to the international standard reference. Within the reference group, approximately 2.3 per cent of the children are underweight. In the developing world, about a quarter (24 per cent) of children under-five are underweight according to the WHO Child Growth Standards.
SOURCES AND DATA COLLECTION
At the national level, data are generally collected from national household surveys, including Demographic and Health Surveys (DHS), Multiple Indicator Cluster Surveys (MICS) and national nutrition surveys. It should be noted that when comparing estimates within a country over time or across countries, these estimates should be based on the same reference population.
DHS and MICS are generally conducted every three-to-five years. Some countries conduct national nutrition surveys annually.
There are some problems with data collection and compilation that may affect the reliability of nutritional status indicators, such as:
- The underweight indicator reflects body mass relative to chronological age and is influenced both by the height of the child, and weight-for-height. Its composite nature complicates its interpretation. For example, the indicator fails to distinguish between short children of adequate body weight and tall, thin children.
- The accuracy of nutritional status indicators depends on proper measurements in age, weight, and height. For example, only those children with month and year of birth recorded and with valid height and weight measurements are included in the calculations.
- In April 2006, the WHO released the WHO Child Growth Standards to replace the widely used National Center for Health Statistics (NCHS)/WHO reference population. Studies have shown important differences between these two reference populations, especially during infancy. Therefore, to allow for comparability over time, it is likely that for some time the anthropometric indicators will have to be analyzed using both the NCHS/WHO and the new WHO Child Growth Standards.
Indicators of malnutrition generally show differences between rural and urban locations and among socioeconomic groups. In some countries, child nutrition may vary across geographical areas, and/or ethnic groups. Gender differences may also be more pronounced in some social and ethnic groups than in others.
Estimates of child undernutrition cross-tabulated by background information are available from most DHS and MICS surveys and from some national nutrition surveys as well.
COMMENTS AND LIMITATIONS
While underweight prevalence is a useful indicator to assess overall nutritional status of the population, stunting and wasting prevalence are also useful indicators for tracking trends in child malnutrition.
Stunting, also known as low height-for-age, measures levels of cumulative deficient growth associated with long-term factors, including chronic insufficient daily protein intake. This indicator is defined as the percentage of children under five whose heights are less than two standard deviations below the median height for the age of the standard reference population.
Wasting, also known as low weight-for-height, indicates in most cases a recent and severe process of weight loss, often associated with acute starvation or severe disease. This indicator is defined as the percentage of children under five whose weights are less than two standard deviations below the median weight for height of the reference population.
When possible, all three indicators (underweight, stunting, and wasting) should be analyzed and presented since they measure and reflect different aspects of child nutrition.
GENDER EQUALITY ISSUES
In most countries, data from national household surveys do not show significant differences in the underweight prevalence of boys and girls. However, these trends should continue to be monitored, particularly at the sub-national level and within subgroups of the population.
DATA FOR GLOBAL AND REGIONAL MONITORING
For international comparisons and global or regional monitoring, the United Nations Children’s Fund (UNICEF) compiles international data series and estimates based on data from national surveys.
UNICEF reviews and compiles survey results reported by individual countries every year and updates its global database on child nutrition indicators. In 2009, UNICEF started to convert its global trend database on child undernutrition from estimates based on the United States National Center for Health Statistics (NCHS)/WHO reference population to estimates based on the new WHO Child Growth Standards by re-analyzing available household survey data.
Estimates may come from different data sources, usually surveys conducted in different years that are recorded and published separately. In rare cases when nationally representative estimates come from different sources in the same year, all sources are included in the global database. However, only one source is selected as the point estimate to be published, and this selection is based on a thorough data quality review.
Regional and global estimates are based on averages weighted by the total number of children under five years of age. These estimates are presented only if available data cover at least 50 per cent of the total children under five years of age in the regional or global groupings.
Latest available estimates of underweight prevalence are published annually in December by UNICEF in The State of the World’s Children
and online. WHO also publishes estimates through its online database: WHO Database on Child Growth and Nutrition.
However, due to slight differences in calculations, there may be discrepancies between the estimates of UNICEF and WHO.
United Nations Children’s Fund (2006). Progress for Children – A Report Card on Nutrition.
New York. Available from http://www.unicef.org/publications/index_33685.html
United Nations Children’s Fund (2007). Progress for Children – A World Fit for Children Statistical Review.
New York. Available from http://www.unicef.org/publications/index_42117.html
World Health Organization. Child Growth Standards.
Geneva. Internet site http://www.who.int/childgrowth
World Health Organization. Global Database on Child Growth and Malnutrition.
Geneva. Internet site http://www.who.int/nutgrowthdb
World Health Organization (annual). World Health Report.
Geneva. Available from http://www.who.int/whr