The overall burden of severe under-5 child malnutrition using the aggregated CISAF values was 11% (12% in rural areas and 10% in urban areas). In contrast, in the same population, the prevalence of severe stunting among children under-5 was 9%. One may speculate that overlap of conventional indicators (i.e. severe stunting, severe wasting and severe underweight) can partly explain this finding. Conventional indicators, therefore, may not provide a comprehensive estimate of the proportion of malnourished children in the population. In contrast, CISAF uses conventional nutritional indicators' aggregate values to estimate the overall burden of severe malnutrition, thus provide a more convincing estimation of the proportion of malnourished children in the population [10]. Our finding of a higher prevalence of severe under-5 malnutrition in rural areas concurs with previous research [20,21,22,23]. Several studies have also reported a higher prevalence of severe under-5 malnutrition in urban areas in Bangladesh with limited geographical coverage [24,25,26]. It should be noted that the rural population is overrepresented in our data, with two out of three (66%) children included in our study lived in rural areas. Approximately 63% of the Bangladeshi population residing in rural areas [27], thus our findings provide an accurate picture of the severe under-5 malnutrition in the country.
The prevalence of severe under-5 child malnutrition was high for children of parents with no formal education. One in four children of parents with no formal education experienced severe malnutrition regardless of being born in rural or urban areas. Further, low birth weight children had a greater odd of being severely malnourish regardless of the rural or urban context. For example, children with low birth weight experienced severe malnutrition 5.03 times more if they lived in urban areas and 2.35 times more if they lived in rural areas. Also, one in five under-5 children born in rural and urban areas with a small birth weight experienced severe malnutrition. Previous studies in Pakistan, Nepal, Malawi, Mexico and Iran also reported children born with small birth weight were more likely to explore malnutrition [13,28,29,3031]. Children born with a low birth weight generally increase their height and weight by small increments [32]. Thus, they may remain shorter and lighter and might be severely malnourished without adequate nutrition support. Children with small birth weights are often born to households with low socio-economic status and poor maternal health conditions [33]. Inadequate feeding practice can contribute to developing under-5 malnutrition due to the irregular distribution of food for children in socio-economically poor households and the knowledge gap of parents/caregivers for appropriate feeding practice. Maternal/parental illiteracy is often associated with low birth weight of child and other determinants including poor maternal healthcare access and caregiving to children, contributing to adverse nutritional outcomes of mothers and children [34, 35]. In our study, 7% of parents were illiterate and 7% of child born with small birth weight that justified the interlink of malnutrition, parental literacy and small birth weight.
Poor socio-economic status is an established risk factor for severe stunting among under-5 children [3,18,36,37]. One in five children who lived in socio-economically poorest households experienced severe under-5 malnutrition. The odds of severe under-5 malnutrition were 2.32 times higher for children lived in rural areas and 1.61 folds higher for those who lived in urban areas if their household was socio-economically poorest. Parents of socio-economically poorest households often can not afford a minimum diet for their children [38].
Parental illiteracy affects children's adverse nutritional outcomes in urban areas, with odds of severe under-5 malnutrition were 2.03 folds higher. In contrast, being born to mothers with no formal education was identified as the most influential risk factor of malnutrition urban areas of Bangladesh [20]. In rural Ethiopia, maternal illiteracy affected children's nutritional status but not a significant risk factor in Pakistan [39,40]. Parental education is a risk factor not been previously reported in Bangladesh and a novel finding of our study. The cost of living is high in urban areas. Educated parents are presented with better job opportunities and higher income, thus can adequately support their children.
Children's birth order ≥ 4 were 1.82 times more likely to experience severely malnourish if they live in urban areas. In a study in Bangladesh by Akram et al. (2018) found children in higher birth order were more likely of being severely malnourished in urban areas, on the other hand, children in higher birth order had more chance of being severely malnourished in rural areas in India [20,41]. Previous studies from Bangladesh, Congo and Ethiopia also reported children with higher birth order were more likely to explore malnutrition regardless of urban-rural context [42,43,44]. Food competition among household's members and the preference of elderly children might cause malnutrition in younger children [2]. The risk of severe malnutrition is usually high in older children (i.e. age 4 to 5 years) in Bangladesh, Nepal, Pakistan, Ethiopia and Congo [45,46,47,48,49]. In comparison, severe malnutrition is high in younger (age 1 to 2 years) children in India [50], indicating this problem's complex nature. We found that toddlers (age 2 to 3 years) living in rural areas had higher odds of severe under-5 malnutrition but not toddlers living in urban areas. Similar level of provision of health and nutritional care available urban children might be the reason of insignificant association between children age and severe malnutrition. Inappropriate feeding behaviours at 6–36 months, and other factors (e.g. infection and food shortage), may be responsible for one-third of malnutrition cases, depending on population, place, time, and season [51]. In addition, lack of attention in rural areas (urban-rural disparities) in case of receiving complementary feeding, access to health services, preventive and curative interventions influence nutrition outcomes [52].
Theoretical insights based on the CISAF aggregated analysis indicates that context-specific individual, community, public policy and environment level of risk factors need to be addressed. The risk difference of severe under-5 child malnutrition between parents with formal education and no formal education was lower in rural areas than in urban areas. Similarly, the risk differences of severe under-5 child malnutrition between children of healthy weight mothers and underweight mothers was lower in rural than that of urban areas. It is possible that in a rural setting, educational attainment and access to health and nutritional care, may not be enough to reduce the burden of severe under-5 child malnutrition owing to the complex interplay between risk factors. Svere malnutrition is a multifaceted, complex phenomenon, involving many immediate causes (such as, insufficient diet habit, child diarrhoea, and ages of breastfeeding children) and underlying causes (such as, income inequality, food insecurity, household dietary diversity, age of introduction of complementary food, access to safe water and environmental hygiene) [53,54]. The risk difference between most affluent and poorest was higher among children in rural areas than urban areas, indicating greater rich-poor gap in rural areas. Socio-economic inequality can be reduced by increasing income-generating activities driven by public and private entities. Such endeavours need to be aimed at deprived and vulnerable individuals and ensure their participation with a standard wage structure under the national nutritional security system. Economic development is associated with improved nutritional status via reducing malnutrition [55]. Improved per capita household income increases available funds for food expenditure and basic health care needs, improving children's nutritional status. Empirical education and standard health care should be made available and accessible to all women in urban and rural areas. Improving access to community-based/empirical education and standard health care to mother will confer many benefits from improved caregiver practices, enhance health and environmental knowledge; increase educated and skilled workforce; live in better neighborhoods, reduce gender-based violence; reduces child marriage and early childbearing; reduces maternal death rates in terms of improved nutritional status and child development [56].