Abstract
Background Reliance on full breastfeeding alone for a longer time could have deleterious nutritional and health implications at later stages of childrens lives. About 47% of children are weaned at age 6 months and more than 50% of children in India under 4 years are stunted. We investigated the association between timing of weaning and stunting of children in India, using the data from National Family Health Survey, 19921993.
Methods Logistic analyses were employed on pooled data comprising one state each from six regions of India (N = 6285) with height status of children aged 24 years as the dependent variable. Timing of weaning was considered as the main control variable in the regression models.
Results Children weaned at age 6 months (odds ratio [OR] = 1.57) and after 6 months (OR = 1.88) were more likely to be stunted at later age compared with those weaned before 6 months (P < 0.001). Stunting appeared to be considerably lower for children weaned at age 3 months and showed an upward trend thereafter. The effect of age at weaning on stunting attenuated but persisted with statistical significance after controlling for important demographic, health, social and region variables. The likelihood of stunting was 77% for children weaned at age >6 months who had not received full immunization in the first year and had lived in poor conditions.
Conclusions Timing of weaning is significantly associated with stunting among children in India. The underlying causal associations between weaning behaviour and growth retardation need to be further examined by using longitudinal data.
Keywords Weaning, stunting, full breastfeeding, complementary feeding, India/regions, logistic models, NFHS, social and health care utilization factors
Accepted 18 March 2002
The health of children is related to many inter-linked biological and behavioural processes; the relative importance of the mothers characteristics and the onset of growth processes from conception to childhood have been well documented in scientific research.15 The Mosley and Chen model on child survival in less developed countries proposed that growth faltering and mortality are the cumulative consequences of multiple disease processes including their bio-social interactions that operate through a set of intermediate variables.1 For example, maternal factors, environmental contamination through infectious agents, nutrient availability, injury, personal illness, and control factors are intermediate variables that affect the malnutrition infections syndrome eventually influencing the demographic outcome.
Among other important intermediate variables, breastfeeding plays a vital role in determining the health and survival of children. Breast milk contains several nutrients and antimicrobial constituents mainly macrophages, lymphocytes and anti-streptococcal factors that protect the baby against viral and bacterial infections.6,7 The age at which complementary foods (CF) are introduced is a sensitive time in infant growth since breast milk alone is insufficient to meet their full nutritional needs. Over time, there has been considerable discussion on the ideal age at introduction of CF and the optimal duration of exclusive breastfeeding.8 The World Health Assembly in 1990, 1992 and 1994 suggested 46 months and about 6 months, respectively, as an ideal age for introducing CF.9 However, the recent WHO/UNICEF guidelines recommend exclusive breastfeeding for 6 months and the introduction of CF at 6 months of age.9,10 Exclusive breastfeeding refers to breastfeeding without offering any CF including plain water/tea. If breast milk is given along with plain water/tea, it is referred to as predominant breastfeeding. The term full breastfeeding (FB) refers to either truly exclusive or predominant breastfeeding.9 The guidelines also suggested that breastfeeding should be continued along with CF until the child is 2 years. This policy is widely adopted particularly in developing countries including India where more than 50% of children <4 years are undernourished.1113 According to the National Family Health Survey (NFHS; 19981999) that recently published the All-India Report, the proportion of undernourished children did not decline much in India compared with NFHS (19921993); the decline is less than 10%.11,14 The NFHS also indicates that breastfeeding is almost universal in India (95%). Mothers continue breastfeeding for more than 2 years and many rely on FB even after 6 months.11,15 Mothers reliance on FB for a longer duration posits a need to examine the growth potentials of their children at later ages.
Some research studies that examined the role of breastfeeding on infant growth pointed out that energy and nutrient supply from breast milk beyond 45 months might be inadequate for meeting an infants nutritional needs.1517 Research in African countries showed that mothers deliberately postpone introduction of CF especially amongst undernourished children.1821 A recent study based on NFHS reported that breastfeeding with an introduction of CF below 4 months is advantageous in reducing early infant mortality in India.22 Timing of weaning is socially and bio-culturally patterned and varies across societies.23,24 It is determined by the mothers characteristics, her choices, her knowledge and perceptions about childs health or cultural beliefs related to breastfeeding.
The main objective of this paper is to examine the associations between timing of weaning and height status of the children at later ages controlling for important demographic, social and health variables. We use the height-for-age (HFA) as an indicator of nutritional status. Height-for-age is unlikely to be influenced by the factors present at survey such as child morbidity, infections/diarrhoea, or food/nutritional intake. A low HFA indicates chronic under-nutrition or nutritional stunting. Height-for-age is a stable measurement of growth and is sensitive to changes in nutritional levels and health status in the past. This study is based on cross-sectional data from the NFHS conducted in India during 19921993. Because of wide inter-state social and cultural differences, a detailed analysis is restricted to one selected state each from six regions of India.
Materials and Methods
Data source
The NFHS is the first nationally representative survey that collected demographic, social, health and anthropometric information simultaneously. The survey was initiated by the Ministry of Health and Family Welfare, Government of India and co-ordinated by the International Institute for Population Sciences, Mumbai. The survey adopted a systematic, stratified sample design of households and collected data from 89 777 ever-married women aged 1349 years from 88 562 households.11 Data was collected between April 1992 and September 1993 from 25 states including Delhi, which comprise 99% of the total population of India.
Description of measures
Stunting
Stunting is defined in terms of HFA. The proportion of children who are more than 2 standard deviation units (z-score) below the median of the international reference population are considered stunted and those who fall more than 3 SD units below are severely undernourished. The z-scores derived using ANTHRO software are based on the NCHS/CDC/WHO international growth reference curves.25 The data from the US Health Examination Surveys were found to be most representative of the growth reference curves that also closely approximated a normal distribution. This international growth reference, approved by a WHO working group on nutritional surveillance, has been widely used and is also found appropriate for measuring the nutritional status of Indian children.26 Detailed descriptions of the reference population have been reported elsewhere.25,27 The NFHS measured height (in centimetres) for each living child born since January 1988. Children aged <2 years were measured lying down and those aged 2 years were measured in standing positions. The anthropometric measurements of children were taken after womens interviews in three phases during 19921993. Height was not measured in the states covered under the first phase because height measuring boards were not available at that time.11 The survey reported that 15.5% of living children were not measured at the all India level. The reasons included were: the mother refused (5.4%), child not present (5.5%), child was sick (1.4%), child refused (2.6%), or other reasons (0.6%). The reasons reported did not differ by states. A negligible proportion (0.2%) of children with grossly improbable measurements are excluded. Childrens age in months is derived from a detailed birth history collected in the survey.
Weaning
In this study, we use the term FB, which may be either truly exclusive or predominant breastfeeding. We define timing of weaning as the age at which FB is concluded by the introduction of either formula, milk other than breast milk, or any other liquids (except plain water), or any solid/mushy foods. Age at weaning was self-reported by mothers for children born since January 1988 until the survey. The NFHS asked the following question. Was the child ever given water or anything else to drink or eat other than breast milk? If children received foods other than breast milk on a regular basis, NFHS recorded the age at introduction of each CF (plain water, formula or milk other than breast milk, any other liquids, any solid/mushy food). Although NFHS made a distinction between plain water and other types of liquids given, it did not collect specific information on the type of other liquids given. In this study, children who were given only plain water along with breast milk are not considered weaned, but those who were given other liquids, which can be sugar/honey water, tea or juice, are considered weaned. If mothers gave CF to children aged <1 month, NFHS coded those responses as 0. In other words the code 0 indicates the first month of life not yet completed. To be precise, in the survey, 4 months is defined as the end of first 4 months of life. For children aged <1 month (pooled data, selected states), 45% received plain water (median: 1 month), 17% received formula or milk other than breast milk (median: 4 months), 3% any other liquids (median: 8 months) and less than 0.5% received solid/mushy foods (median: 10 months). We found age heaping at the 0th, 6th and 12th months in the data, especially in the states where female literacy is low, for example in Uttar Pradesh (UP) and Bihar. About 1% of children (pooled data; N = 7822) were excluded from the analysis since mothers did not report age at weaning (0.6%) or reported not to have given any CF (0.5%).
Statistical analysis
Logistic regression models are used with a dichotomized classification of z-scores based on height status as the dependent variable. Stunted children are coded 1 and well-nourished are coded as the reference group. Timing of weaning is classified as an independent variable. We coded weaning at age <6 months as the reference category. This classification is made to understand the effect of weaning on stunting particularly at 6 months and after. We purposefully selected children aged 2447 months (N = 6285) whose height was measured in order to analyse weaning initiation behaviour without censoring problems. For example, it is possible that some children below 2 years could be under FB at survey. Since the effect of age at weaning on stunting could be influenced by factors such as age or mothers education, we controlled for some important demographic, social and health factors in the regression models. We used weighted data to adjust sampling variations.11 Multicollinearity problems are considered and variables that are significant in the likelihood ratio tests are included in the regression models.
Results
Based on the z-scores, the NFHS data indicate that more than one-half of children aged under 4 years in India are stunted and more than a quarter are severely undernourished (Table 1). The northern, the central and the eastern states are particularly disadvantaged in terms of proportion stunted, about 60% each in Bihar and UP. The proportion of undernourished children is comparatively low in the north-eastern states. The position of Kerala and Goa, where health care utilization is high, is different from other states.
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Over 60% of children weaned at 6 months of age are stunted and age variations are apparent, though fluctuating, over different age groups (Table 2
). The prevalence of stunting is high among children aged 4247 months who are weaned at
6 months. The sex differences appear to be tenuous in the selected states except Assam and Goa (Table 3
). Although stunting is generally a little higher among males, females weaned at age 6 months are comparatively more stunted than males in Punjab and Goa.
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The overall prevalence of stunting is extremely high in India. The introduction of CF below 6 months of age significantly reduces stunting among children aged 2447 months in India. Sex differentials in relation to timing of weaning and stunting are insignificant. The effect of age at weaning on stunting persisted with higher statistical significance both in the presence and absence of other important control variables. Nevertheless, the inclusion of demographic, health, social and region variables mediated and attenuated the weaning effects on stunting. Contrary to existing policy recommendations, our study suggests that reliance on FB alone to 6 months may not be a good solution for the optimal growth of children. Stunting appears to be comparatively lower for children weaned at completed age 3 months.
Weaning is socially and culturally influenced within and across Indian regions. We found that children born in Punjab or Goa are comparatively well nourished where CF is introduced relatively early. The situation is different in states, for example Bihar and UP, where female education, health care utilization and living conditions are comparatively poorer than in other states. Whilst it concerns poverty, mothers may have less options to initiate early weaning, they rather rely on FB.2931 Formula/milk foods that are usually expensive to buy seem to play little role in the states that are still caught up in poverty with large families. An option could be to educate mothers about when and how to start weaning with an emphasis on the use of better home made weaning foods.32
This study has some limitations. Unfortunately, we could not derive from the survey whether stunting precedes or follows late introduction of CF. A reverse causality (malnutrition causing late introduction or late introduction causing malnutrition), as found in African studies, might be plausible in India. Moreover, we do not have information in the survey about the type of CF introduced at the time of weaning and in later periods, which could also influence the growth of children. Mothers response on age at weaning is considered quite reliable since the recall period was closer to survey time. It should, however, be noted that since weaning heaps at age 6 months, the weaning effects at age 6 months could be overestimated. More in-depth and longitudinal studies are needed to disentangle the underlying mechanisms and the chain of factors associated with breastfeeding and weaning behaviour and their subsequent influence on the growth of children.
KEY MESSAGES
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Acknowledgments
We gratefully acknowledge the editorial remarks and invaluable comments and suggestions provided by two anonymous reviewers. We also thank PN Mari Bhat for his constructive comments and discussion on an earlier version of this paper.
Notes
Population Research Centre, Faculty of Spatial Sciences, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands.
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