What is Stunting?
Stunting is defined as impaired growth and development in children due to factors like poor nutrition and repeated infections. It serves as a key indicator of chronic undernutrition, marked by a child's height-for-age being significantly below the median of a reference population. A child is considered stunted if their Height-for-Age Z-score (HAZ) is below -2 standard deviations of the World Health Organization (WHO) Child Growth Standards median. This condition has long-term impacts on cognitive development and overall health. Stunting reflects cumulative, long-term deprivation, differentiating it from wasting, which indicates acute undernutrition.
The World Health Organization's Role in Measurement
The WHO standardizes stunting calculation globally using Child Growth Standards developed in 2006. These standards, based on healthy, breastfed children, provide a normative model for growth and replace older references for better global comparability. The WHO also offers software like WHO Anthro to assist in calculating anthropometric indices, ensuring data quality and consistency.
The Calculation Process: Step-by-Step
Calculating stunting involves obtaining accurate physical measurements based on the child's age (length for under 24 months, height for 24 months and older). These measurements are then compared to the WHO Child Growth Standards, providing median values and standard deviations for height-for-age by sex and age. The core calculation is the Height-for-Age Z-score (HAZ). The Z-score is typically calculated using specialized software, which uses methods like the LMS method to account for data characteristics. The resulting Z-score is then interpreted based on WHO cut-off points to classify the child's nutritional status. For detailed information on the calculation steps, refer to {Link: The DHS Program https://dhsprogram.com/data/Guide-to-DHS-Statistics/Nutritional_Status.htm}.
WHO Z-Score Classification for Stunting
| Z-Score Range | Classification | Description |
|---|---|---|
| Z-score $\ge$ -2 | Normal | Child's growth is within the normal range for their age and sex. |
| Z-score $\lt$ -2 and $\ge$ -3 | Moderately Stunted | Child's height-for-age is significantly low, indicating moderate, long-term undernutrition. |
| Z-score $\lt$ -3 | Severely Stunted | Child's height-for-age is extremely low, indicating severe, long-term undernutrition and chronic growth failure. |
Tracking a child's growth over time with multiple Z-scores offers a more comprehensive view of their growth pattern.
Key Factors Influencing Stunting
Several factors contribute to stunting risk:
- Maternal Health: Poor maternal nutrition and health impact fetal growth.
- Feeding Practices: Inadequate infant and young child feeding contributes to deficiencies.
- Infections: Frequent illnesses hinder nutrient absorption.
- Socioeconomic Factors: Poverty, food insecurity, and poor sanitation are major drivers.
- Environment: Poor hygiene increases exposure to pathogens.
Conclusion
Calculating stunting relies on the systematic use of the Height-for-Age Z-score (HAZ) and the WHO Child Growth Standards. This process, from accurate measurement to Z-score interpretation, is vital for clinicians and public health officials. Standardized assessment helps identify children with long-term nutritional deprivation, facilitates targeted interventions, and monitors progress in child health globally. Accurate stunting classification provides a crucial metric for understanding population health and guiding nutrition policies. For detailed information and tools, refer to the {Link: WHO website https://www.who.int/tools/child-growth-standards}.
