Approaches to the study of stunting

Three possible approaches are suggested here. The outcomes are perceived as the minimum information that should be collected. It should be noted that a considerable amount of additional time may be needed to recruit subjects of the right age and type (especially pregnant women), to stagger enrollment so that personnel can handle the measures, and to capture and analyse the data.

1. Research focused on the prevention of stunting

Subjects: Fetuses from conception up to children 2 years of age. This postnatal period usually involves three stages of feeding: breast-feeding, often relatively exclusive for 4-6 months; weaning, until the time when partial breast-feeding ends; and the post-weaning period. The nutritional causes of stunting may well differ among these periods. There are also two phases of growth in early postnatal life; an infancy phase (starting in mid-gestation and declining in importance up to 3-4 years after birth), and a childhood phase that starts around 8 months of life in well-nourished children and several months later in those who are malnourished (see paper by Karlberg et al., pp. 25-44).

Interventions: Select the kind of intervention that seems most likely to be effective in the particular setting, in the light of what is known about diet, disease incidence, etc. Examples might be supplementation during pregnancy, supplements to the infant of protein, trace elements, etc; there should be a separate group of children for each intervention. A control group is desirable of children from the same background, with the same risk of becoming stunted (this can be assessed approximately from the heights of mothers and sibs). Postnatal interventions should start as soon after birth as possible, preferably not later than two months. Outcome: Outcome measures should include length and lower leg length measurements made monthly for the first year and thereafter every three months, and growth velocity over 3- to 6-month intervals. Only with measurements of this frequency will it be possible to detect a delay in the entrance into the child phase. If the intervention is a supplement which has to be given every day under supervision, monthly measurements should not involve much extra work load. If the intervention is the elimination of parasites, longer intervals between measurements may be permissible, dictated by the intervals chosen for controlling for parasitic and infectious disease.

2. Research focused on the reversibility of stunting before puberty

Subjects: Preschool or school age children who are more than 2 SD below reference length for age.

Interventions: Test whether nutritional improvement can enhance linear growth without accelerating bone age maturation beyond chronological age. Suggested examples are supplementation with specific minerals, vitamins or key amino acids for anabolism.

Outcome: Linear growth velocity over a 2-year period, changes in bone age.

3. Research focused on the reversibility of stunting at the time of peak linear growth velocity at puberty

Subjects: Children 10-11 years of age who are more than 2 SD below reference length-forage.

Interventions: Test whether nutritional improvement or physical exercise can enhance linear growth without accelerating bone age maturation beyond chronological age or length age. Potential interventions include nutrients such as zinc or protein, or physical exercise, which might modify the hormonal responses that enhance linear growth during this critical period.

Outcomes: Final adult height, or height in the middle of the first 1-year interval after age at peak growth velocity (see paper of Karlberg et al., pp. 25-44).