Urban-rural differences in the associated factors of severe under-5 child undernutrition based on the composite index of severe anthropometric failure (CISAF) in Bangladesh

Severe nutritional indicators for under-5 children were categorised into seven groups: (A) no severe failure; (B) severe wasting only; (C) severe wasting and severe underweight; (D) severe wasting and severe stunting and severe underweight; (E) severe stunting and severe underweight; (F) severe stunting only; and (G) severe underweight only (Table 1). A child is considered having severe undernutrition if she/he has any anthropometric failure from B to G (Fig. 2).

The primary outcome measure was severe under-5 child undernutrition using the CISAF. A child was considered to be severely stunted and severely wasted and severely underweight if the z-scores of length/height-for-age, weight-for-height/length, and weight-for-age were below minus three (− 3.0) Standard Deviations (SD) (i.e., HAZ/LAZ < −3SD; WHZ/WLZ < −3SD; WAZ < −3SD) below the respective median of the World Health Organization (WHO) reference population, respectively [18]. Children without any anthropometric failure from B to G, that is, with moderate undernutrition and/or normal children were categorized as ‘no severe failure’.

Independent variables were selected based on the previously identified socioeconomic factors [5, 11, 17, 19, 20]. These variables include maternal age in years (15–19, 20–24, 25–29, 30–34, 35–39, ≥40); parents’ education (both parents uneducated, only father was uneducated when mother was educated, only mother was uneducated when father was educated, both parents educated); mother’s current income-earning status (not working, currently working); underweight mother (if the Body Mass Index (BMI) is below 18.5 kgm^− 2, then ‘yes’; if BMI ≥ 18.5 kgm^− 2, then ‘no’); mothers received antenatal care (no, yes); received postnatal care (no, yes); mother’s attitudes toward wife-beating (‘justified’ if mothers agree that a husband is justified in hitting or beating his wife if she went out without telling him or/and neglected the children or/and she ever argued with her partner or/and burned food or/and refused to have sex; otherwise ‘not justified’) [8]; decision-making autonomy (‘participated’, if women make decisions alone or jointly with their husband in all three of the following areas: (1) their own health care, (2) major household purchases, and (3) visits to their family or relatives; otherwise, ‘not participated’) [8]; religion (Islam, others); source of drinking water (improved, unimproved) [8], cooking fuel [‘solid fuel’ (including charcoal, wood, straw/shrubs/grass, agricultural crops, and animal dung), and ‘clean fuel’ (including electricity and LPG/natural gas/biogas)] [8]; mass media exposure (no, yes: exposure to either radio, television, newspapers, or magazines at least once a week), wealth index (integrating household asset ownership and access to drinking water and sanitation) [8]. Moreover, factors related to children, such as age, birth order, and birth weight status [21, 22], recent morbidity status (child had at least one morbid condition out of diarrhea, fever and cough in the two weeks preceding the survey) [8] were included. The detailed construction procedures of all independent variables were tabulated in the Additional Table 1.

Socioeconomic characteristics were analysed using descriptive statistics. Bivariate association was used to determine the proportional differences of variables between non-severe undernutrition and severe undernutrition group. The significance level for bivariate analysis was set at P < 0.10 (2-tailed). Independent variables that were significant in bivariate analysis were simultaneously entered into the logistic regression models for the adjustment to identify the associated socioeconomic factors of severe undernutrition, measured by CISAF. Results were derived using a stepwise backward selection of regression and expressed by the adjusted odds ratio (AOR) and 95% confidence interval (95% CI). The significance level for logistic regression analysis was set at P < 0.05. To control the effect of the complex survey design, all the analyses of this study were performed using Stata’s ‘SVY’ command. Variance Inflation Factor (VIF) was used to evaluate the possible collinearity. However, there was no multicollinearity problem among the variables. All statistical analyses were performed in Stata version 14.2 (StataCorp LP, College Station, Texas).

Of the 7661 under-5 children, about two-thirds lived in rural areas. Three-quarters of the mothers were aged below 30. In rural areas, families were comparatively least wealthy than the urban families (rural 54.3% vs. urban 19.4%), and more mothers were underweight (rural 16% vs. urban 12.1%). In approximately 82% of cases, both parents were educated, whereas nearly 4% of parents were uneducated, regardless of urban-rural settlement. Access to mass media was higher in urban areas (rural 56% vs. urban 79%). Around 40% of the children were aged under 23 months. More than half of the children were not weighted during their birth. And nearly half of the children (47.2%) had recently suffered from any morbidity condition (Table 2).

The overall prevalence of severe undernutrition measured by CISAF among the children under-5 was 11.0% in Bangladesh (rural 11.5% vs. urban 9.6%) (Table 3). Figure 2 shows that the overall prevalences of severe stunting, severe wasting, and severe underweight were 9%, 1.5%, and 4.1%, respectively. The prevalence of severe stunting (9.7% vs. 7.7%) and severe underweight (4.2% vs. 3.7%) was higher in rural areas than in the urban (Fig. 2). In terms of regional prevalence, the Sylhet region reported the highest prevalence of severe under-5 child undernutrition in both rural (16.9%) and urban areas (13%) (Fig. 3).

From the bivariate association, in both urban and rural areas, children of uneducated parents (urban: 25.9% vs 8.4%; rural: 21.5% vs 9.8%), underweight mothers (urban: 15.4% vs 8.9%; rural: 17.1% vs 10.5%), poorest households (urban: 18.7% vs 6.4%; rural: 16.1% vs 5.0%), and with small birth weight (urban: 18.3% vs 6.6%; rural:) reported a higher prevalence of severe under-5 undernutrition than the children of educated parents, normal BMI mothers, richest households, and normal birth weight (Table 3).

The key associated factors for under-5 undernutrition in urban areas were: children born with small birth weight (Adjusted Odds Ratio, AOR: 3.99, 95% CI: 2.12, 7.52) vs. healthy weight; children of parents with no formal education (AOR: 2.34, 95% CI: 1.27, 4.32) vs. children of educated parents; mothers did not receive postnatal care (AOR: 2.13, 95% CI: 1.32, 3.44) vs. the recipient mothers; children’s birth order ≥4 (AOR: 1.75, 95% CI: 1.97, 2.86) vs. children’s first birth order; poorest children (AOR: 2.40, 95% CI: 1.47, 3.93) vs. the richest; and children of underweight mothers (AOR: 1.58, 95% CI: 1.04, 2.40) vs. normal mothers (Table 4).

On the other hand, in the rural areas, children born with small birth weight (AOR: 2.84, 95% CI: 1.88, 4.30) vs. healthy weight; children who lived in poorest households (AOR: 2.44, 95% CI: 1.57, 3.78) vs. the richest households; children aged less than 36 months (for age group 24–35 months (AOR: 2.10, 95% CI: 1.61, 2.74); for age group 12–23 months (AOR: 1.78, 95% CI: 1.36, 2.33)) vs. children of age group 0–11 months; children of mothers with no formal education (when fathers are educated) (AOR: 2.15, 95% CI: 1.46, 3.18) vs. children of educated parents, etc. socioeconomic factors showed a positive association with severe under-5 undernutrition (Table 4).

The BDHS 2017–18 data used for this study was one of Bangladesh’s largest nationally representative samples. The stability of the data set allows changes over time to be monitored with some confidence. However, there were some limitations too for this study. First, we could not use the infant and young children feeding data to the models because the data available in the BDHS were only for the children aged 6 to 23 months. But our study considered children under age 5. So, there would be too many missing variables, and this study would be limited only to children under age 2. Further, data on potential confounders like diet, food insecurity, and parents smoking behavior were unavailable. Secondly, the cross-sectional data was insufficient to establish a causal relationship, consequently limiting the findings’ applicability. Thirdly, the BDHS data were collected retrospectively and self-reported, thus subject to underreporting, information bias, and recall bias. However, data were collected using validated tools and standard procedures. Using seven nutritional status measurements, CISAF provided a credible estimate of the overall proportion of severe under-5 child undernutrition and the complex interplay between individual, community, public policy, and environment level associated factors.