Growth and development in the earliest years of life are fundamental for the future of every individual and for the future of the societies in which those individuals are born. The two periods of highest vulnerability for growth faltering are during intrauterine development and from birth to 36 months of age (Shrimpton 2001). In infancy and early childhood common causes of malnutrition are: 1) inappropriate feeding practices such as lack of exclusive breastfeeding and the too early introduction of weaning foods, and 2) receiving diets of poor quality and in inadequate quantity (WHO 1999).
Research indicates that 15% of the global burden of disease can be attributed to the joint effects of childhood and maternal underweight or micronutrient deficiencies (Ezzati 2002). The World Health Report 2002 shows that 170 million children in poor countries are underweight, and over three million of them die each year as a result (WHO 2002). Malnutrition and infection are closely related to high morbidity and mortality under circumstances of high exposure to infectious diseases and inadequate diet. Furthermore, this association not only claims the lives of millions of children throughout the world, but also damages their growth and development, diminishes their quality of life in the present, and compromises their future.
Food supplementation, defined as the provision of extra food to children or families beyond the normal ration of their home diets, is an intervention aimed at improving the nutritional status or preventing the nutritional deterioration of the target population (Beaton 1982). Young children could consume the supplementary food at a supervised local feeding centre or at home. Both approaches carry many implications that should be considered when assessing the effectiveness of this nutritional intervention. In the former approach, the family should be motivated to participate daily, and someone has to be able to deliver the child to the centre each day, and therefore the centre should be in reasonably close proximity to the home. Further, personnel are needed to prepare and serve the food as well as record and control participation. The take-home food approach permits a greater geographic separation between those distributing the food and the home, and hence requires fewer staff. However, the impact on the intended beneficiaries is probably less efficient due to the fact that food delivered to the home may well be shared with other family members (Beaton 1982).
The impact of food supplementation programmes on child physical growth merits careful scrutiny, in view of the costs and their current implementation, which involves thousands of children worldwide. Randomised controlled trials are widely accepted to be the best method for minimizing systematic errors (bias) when assessing the effects of health care interventions (Chalmers 1983, Villar 1996). The proper use of randomisation guarantees that there is no bias in the selection of patients and enables trial conclusions to be more reliable than other methods of treatment allocation (Pocock 1990).
In preparing this protocol, we recognize that supplementary feeding for young children in developing countries may ameliorate the current situation, and may contribute indirectly to a long-term improvement, but it does not, in and of itself, represent a solution to the fundamental health and nutritional problems that face families living in poverty. In this context, diarrhoea and infectious diseases may interfere with the potentially beneficial effect of extra feeding. Improvements relating to food safety, housing, water supply, and sanitation are important steps towards tackling malnutrition and this viewpoint will be considered when interpreting the results. The development of appropriate combinations of interventions aimed at preventing or treating impaired growth in young children should be a priority because growth deficits after birth and during the earliest years are not generally recovered, even with adequate feeding in later years (WHO 1999).
This systematic review will assess the effectiveness of one potential intervention for reducing socio-economic inequalities in the health and development of young children: community-based supplementary feeding. The review is intended to support the vision of those governments and leading international organizations which are placing increasing emphasis on evidence-based strategies to promote a world where people everywhere, at every age, enjoy an adequate level of nutritional well-being free from all forms of malnutrition (WHO 2000).
To examine systematically the effectiveness of community-based supplementary feeding programmes in improving physical growth in young (pre-school) children.
Criteria for considering studies for this review
Types of studies
Randomised controlled trials (cluster randomisation or randomisation of individuals). We will include either no treatment controls (home diet or no feeding) or placebo controls (e.g. very low energy-protein foods or drinks).
Types of participants
Children in developing countries born at term (>=37 completed weeks of gestation) aged 0-5 years old will be considered. Children with malnutrition not resulting from insufficient dietary intake, e.g., cystic fibrosis, will be excluded.
Types of intervention
Community-based supplementary feeding programmes or food supplementation will be defined as the provision of extra food (at a feeding centre or at home) to children or families beyond the normal rations of their home diets.
Supplementary feeding could comprise:
-meals (local or imported foods)
-drinks (juices or milk)
-snacks (including both food and milk snacks).
Types of outcome measures
We will consider the following outcome measures:
Primary outcome measures will be:
1) Change in weight expressed in kg or weight-for-age (W-F-A) z-score
2) Change in length/height expressed in cm or length/height-for-age z-score
3) Change in weight-for-height (W-F-H) z-score
4) Prevalence of underweight (weight-for-age below -2 standard deviation from the reference median value of the NCHS/WHO)
5) Prevalence of stunting (height-for-age below -2 standard deviation from the reference median value of NCHS/WHO)
6) Prevalence of wasting (weight-for-height below -2 standard deviation from the reference median value of the NCHS/WHO)
Secondary outcome measures will be:
7) Absolute values of head circumference (front-occipital circumference) in cm
8) Absolute values of mid-upper-arm circumference in cm
9) Absolute values of skinfold thickness (subscapular, tricipital) in mm
Search strategy for identification of studies
See: Cochrane Developmental, Psychosocial and Learning Problems Group search strategy
See: Collaborative Review Group search strategy
In addition to the database of clinical trials maintained by the Cochrane Developmental, Psychosocial and Learning Problems Review Group, the following search terms will be used to search the Cochrane Controlled Trials Register (CENTRAL), MEDLINE, EMBASE, CINAHL, LILACS, Health Development Agency database of interventions to reduce health inequity, Social Science Index, and Dissertation Abstracts International. Where necessary, the search terms will be modified to suit the requirements of particular databases. No language limitations will be applied.
The search strategy will include the following terms: (child* OR infan* OR baby OR babies OR pre-school* OR preschool*) AND ( (feeding OR food OR dietary OR nutrition*) AND supplement*) AND (growth OR anthropometr* OR weight OR height OR length)
(child* or infan* or baby or babies or pre-school* or preschool*)
0 0 0 0 0
(food or feeding or diet* or nutrition*)
0 0 0 0 0
0 0 0 0 0
(growth or anthropometr* or weight or height or length)
0 0 0 0 0
(#2 and #3)
0 0 0 0 0
(#1 and #4 and #5)
0 0 0 0 0
Key people from organizations focusing on nutrition, hunger, and international development will be contacted by email. These e-mails will introduce our review, and ask for help in identifying studies on feeding programs which we may have missed. The organisations we intend to approach are listed below:
World Food Program: http://www.wfp.org
Asian Development Bank: http://www.adb.org
The World Health Organization: http://www.who.int
International Food Policy Research Institute
UNESCO: United Nations System Standing Committee on Nutrition (SCN) www.unsystem.org/scn
The UK Department for International Development
The United States Department on International Development
References of retrieved articles and relevant reviews will be scanned for potentially eligible studies. An attempt will be made to identify other relevant trials from discussions with experts in the field and from conference proceedings. Letters to experts in the field will be sent asking for help in identifying additional studies.
Methods of the review
1. Selection of trials
Titles and abstracts of articles retrieved by the electronic searches or by other method will be assessed independently by two reviewers (GC and YS) to determine whether they might meet the inclusion criteria. Reviewers will not be blinded to the names of the authors, institutions or journal of publication. Differences of opinion about suitability for inclusion will be resolved by discussion. Any doubt during this process will be resolved by consultation with a third reviewer (M de O) or through discussion with the editorial base. If necessary, further information will be sought from trialists. Any such trials will be added to the list of those awaiting assessment while further information is awaited.
2. Data extraction
Data will be extracted independently by two reviewers (GC and YS). The following data will be recorded on data extraction forms: method of random allocation to treatment/control groups, details about participants, description and length of the intervention, description of co-interventions, data on outcomes related to child physical growth, and rates of withdrawals. Any disagreement between the reviewers will be discussed and, when necessary, a third reviewer (M de O) will be consulted.
3. Quality assessment
Two reviewers (GC and YS) will independently assess each included study on a number of criteria, in particular:
* Allocation concealment to intervention groups (protection against selection bias)
Allocation concealment will be defined as below, as per the Cochrane Reviewer's Handbook (Alderson 2004):
(A) indicates adequate concealment of allocation (e.g. by sealed envelopes).
(B) indicates uncertainty about whether the allocation was adequately concealed (e.g. possibly where the method of allocation concealment is unknown).
(C) indicates that the allocation was definitely not adequately concealed (e.g. open random number lists or quasi-randomisation methods).
Trials in all categories will be included in the review, but only trials that are allocated to categories A and B in relation to allocation concealment will be included in any meta-analysis.
* Blinding in outcome assessment (protection against detection bias)
Blinding will be rated as below:
MET: assessor unaware of the assigned treatment when collecting outcome measures.
UNCLEAR: blinding of assessor not reported and cannot be verified by contacting investigators.
NOT MET: assessor aware of the assigned treatment when collecting outcome measures.
* Losses to follow-up will be classified as follows:
ADEQUATE: loss to follow-up less than 20% in each of the comparison groups.
UNCLEAR: losses to follow-up not reported.
INADEQUATE: losses to follow-up equal or greater than 20% in any of the comparison groups.
Trials will not be included for assessment if 20% or more participants were excluded from the analysis in any of the comparison groups.
* Intention-to-treat will be rated as below:
MET: intention-to-treat analysis performed or possible with data provided.
UNCLEAR: intention-to-treat analysis not reported, and cannot be verified by contacting the investigators.
NOT MET: intention-to-treat analysis not done and not possible with data provided.
* Reliable primary outcome measure(s):
ADEQUATE: if anthropometric measures such as weight and length/height are well-described and methods are in line with established protocols. Important details would be training of the anthropometric team, number of replicates of measurements, and type and calibration of equipment.
UNCLEAR: if anthropometric measures and methods of measurements are not clearly described.
INADEQUATE: if the anthropometric team is not trained, if the methods are not described in detail, and if equipment is not well-calibrated.
4. Measurement of treatment effect
Statistical analysis will be carried out using the RevMan 4.2.7 software. Results will be presented as relative risks for dichotomous data, and weighted mean differences for continuous data will be assessed where possible, both with 95 per cent confidence intervals.
5. Data management
Information on study design and implementation, sample characteristics, intervention characteristics, and outcomes will be extracted from studies and coded on a data extraction form. Two reviewers (YS and GC) will independently code all studies. Differences between coders will be resolved in order to refine coding schemes and establish inter-rater reliability. Citations and data will be entered and organized in RevMan 4.2.7. Authors of studies with missing data will be contacted.
6. Data synthesis and analysis
Data synthesis will be conducted with RevMan 4.2.7, the latest version of the Cochrane Collaboration's meta-analysis software.
6a. Continuous data will be analyzed if means and standard deviations were available and there is no clear evidence of skew in the distribution. Where scales measured the same clinical outcomes in different ways, standardized mean differences (SMD) will be compared across studies. The RevMan formula for SMD is Hedge's g, which is like Cohen's d but includes an adjustment for small sample bias. Inverse variance methods will be used to pool SMDs, so that each effect size is weighted by the inverse of its variance in an overall estimate of effect size. Confidence intervals of 95% will be used for individual study data and pooled estimates.
6b. Binary outcomes will be analyzed by calculating odds ratios with 95% confidence intervals. Although the odds ratio provides an effect for use in meta-analysis (Lipsey 2001), attempts will be made to preserve information about base rates (actual proportions) and differences in proportions, since this information is of interest to policy makers. RevMan 4.2 .7 uses Mantel-Haenszel methods for combining binary outcome data across studies.
If some primary studies report an outcome as a dichotomous measure and others use a continuous measure of the same construct, two separate meta-analyses will be used (one for odds ratios and another for SMDs). When a primary outcome study provides multiple measures of the same construct at the same point in time, an average effect size will be used to avoid dependence problems. When a primary outcome study reports multiple measures of the same construct at different points in time, we will use a single measure that is closest to a one-year follow-up.
7. Assessing and exploring heterogeneity
Consistency of results will be assessed visually and by examining I
If heterogeneity exists, we will examine potential sources using the following steps:
- Subgroup analyses (see below)
- Meta-regression (see below)
- Sensitivity analysis (see below)
8. Subgroup analyses:
The impact of certain study characteristics thought likely to influence the impact of supplementary feeding on growth will be investigated by means of sub-group analyses. Depending on the data reported in the included studies, the following sub-group analyses will be undertaken:
(i) the differential impact of studies including children younger than 24 months
(ii) the differential impact of studies conducted in malnourished infants, defined as underweight (weight-for-age below -2 standard deviation from the reference median value of the NCHS/WHO), stunting (height-for-age below -2 standard deviation from the reference median value of NCHS/WHO), and wasting (weight-for-height below -2 standard deviation from the reference median value of the NCHS/WHO)
(iii) the differential impact of studies based on supplementary feeding programmes lasting more than 12 months.
Sub-group analyses may also be conducted in relation to differences in the type of delivery of food supplementation such as feeding centre/ at home and inequalities in the caloric density and nutrient content of food rations. However, sub-group analyses should be treated with caution (so as to avoid the pitfall of asserting causal links) and such issues will be considered in the textual discussion.
If statistically significant heterogeneity is identified, and an adequate number of trials are included, meta-regression will be conducted to examine the effects of these characteristics of supplementary feeding programmes on the results: age of the children, nutritional status of the children at the beginning of the intervention, and duration of supplementation.
10. Sensitivity analyses
If required, sensitivity analyses will be performed to evaluate whether the pooled effect sizes are robust across components of methodological quality. In line with the methodological criteria assessed, we will conduct sensitivity analysis for each major component of the quality form such as concealment allocation and blinded assessment.
11. Use of qualitative research
The narrative review will draw on available qualitative data within studies to discuss program processes, content and implementation issues.
12. Use of data on program costs
We will summarize available data on the costs of programs within the 'Description of studies' , if such data are provided or reported in the original studies.
13. Assessment of bias
Funnel plots (effect size against standard error) will be drawn if sufficient studies are found. Asymmetry could be due to publication bias, but they can also be due to a relationship between trial size and effect size. In the event that a relationship is found, clinical diversity of the studies will also be examined as a possible explanation (Egger 1997).
Potential conflict of interest
We would like to thank Geraldine Macdonald and Jane Dennis of the Cochrane Developmental, Psychosocial and Learning Problems Group for valuable advice and assistance. We are also grateful to Shailen Nandy of the University of Bristol, England, for his suggestions on the background section.
Sources of support
External sources of support
- Department of Nutrition. World Health Organization , Geneva SWITZERLAND
Internal sources of support
- Centro Rosarino de Estudios Perinatales (CREP), Rosario ARGENTINA