Determinants of underweight among children aged 0–23 months in Tanzania

Abstract Underweight is the most dependable growth indicator for overall child growth. Tanzania has the highest rate of underweight children in East Africa, with 1.27 million children under the age of five suffering from the condition. This study aimed to determine factors that influence underweight in Tanzanian children aged 0–23 months. We used data from the Tanzania Demographic and Health Survey (TDHS) 2015–2016 to conduct secondary analysis on a sample of 4,327 children aged 0–23 months. Descriptive and inferential statistics such as frequency, chi‐square, binary, and multivariate logistic regression were performed using the Statistical Package of Social Science (SPSS version 25). Statistical significance was defined as a p‐value of less than 0.05. Multivariate analysis found risk factors for underweight children were as follows: child's gender, age, birth weight, mothers' BMI, level of education, and type of toilet facility used by the households. Females had a significantly lower risk of being underweight (AOR = 0.62, 95% CI = 0.48–0.81, p < .05) compared with male children. The odds of being underweight increase with low birth weight (AOR = 2.92, 95% CI = 1.92–4.43, p < .05), low mother's BMI (AOR = 2.48, 95% CI = 1.34–4.58, p < .05), and low educational level (AOR = 1.78, 95% CI = 1.23–2.58, p < .05). Nutrition interventions such as growth monitoring, nutrition counseling, and nutrition education for parents/caregivers are critical to ensuring proper weight gain for all children under 2 years of age.

children under the age of five were underweight, of which 40% were under two (United Republic of Tanzania, 2019).
Other studies suggest a significant association between being underweight and consanguinity, late initiation of breastfeeding, dietary diversity, inadequate food intake, frequency of feeding, and poor complimentary food (Hasnain & Hashmi, 2009;Asfaw et al., 2015 andIdris et al., 2012). Also, the mother's BMI, gender of family's head, family size, and maternal age correlate with being underweight for a child (Nyaruhucha et al., 2006;Nolla et al., 2014 andSapkota, 2009). Similarly, poor access to clean drinking water, type of resident (rural or urban), presence and use of toilets, hand washing habits, and episodes of diarrhea are associated with underweight in children under the age of five (Demilew & Abie, 2017;Yisak et al., 2015).
While there has been a reduction of underweight prevalence to 14.6% in Tanzania, the prevalence is still an alarming threat, affecting an equivalent estimate of 1.27 million under-five children every year (United Republic of Tanzania, 2019). The World Health Organization (WHO) categorizes the severity of underweight prevalence within the range of 10%-19% among children under 5 years of age as medium (WHO, 1997). It is worth noting that the mortality risk has no exception either to mildly underweight or severely underweight children; both are at greater risk (Rodriguez-leyva & Pierce, 2021). The country is still experiencing a mortality rate of 38.4% attributed to unsafe water, unsafe sanitation, and lack of hygiene. In addressing the consequences of malnutrition, the country implements interventions largely focused on addressing the immediate causes, underlying causes, and basic causes of under nutrition. These are well stipulated in the National Multi-sectorial Nutrition Action Plan (NMNAP) (United Republic of Tanzania, 2019). A combination of nutrition interventions with environmental sanitation strategies like waste disposal, access to clean water, and use of clean household fuels is guided by evidence to policy to action for 5 years.
In Tanzania, limited research evidence exists which explores the determinants of underweight for children aged between 0 and 23 months. Most of these studies targeted specific regions and all children under 5 years of age without considering the critical child age from 0 to 23 months. Any form of malnutrition in this age group is an alarming threat since its consequences may persist even in adults and they cannot be reversed. Therefore, this study aimed to find out what factors influence underweight in Tanzanian children aged 0-23 months. The findings of this study will help nutrition stakeholders plan and create nutrition programs that will reduce underweight in this age group, ensuring their lives and the economic advancement of future generations. Also, contribute to achieving sustainable development goal number 2, which aims to eliminate all types of malnutrition by 2030.

| ME THODOLOGY
The study examined the secondary data obtained from the Tanzania with a precision of 100 g. The weighing was done on a naked child as recommended for anthropometric methods, and if a mother/ caregiver refused to remove clothes for her child, the enumerators recorded the weight as per instruction. A younger child who was not able to stand on the scale was measured on his/her caregiver's hand using the mother-to-baby function of the scale. The obtained weight was entered into the WHO standard software to give underweight, that is, weight for age Z-scores. The child was considered to be underweight if his/her weight for age Z-score (WAZ) was below −2 SD, grouped as moderate underweight when the weight for age Z-score ranged from −2 to −3 SD, and severe underweight if the weight for age Z-score ranged below −3 SD. The calculated weight for the age Z-score (WAZ) was based on 2006 WHO standards.
To determine the risk factors, the underweight was analyzed against independent variables at the individual, mother, and household level. Individual-level were child age, sex, birth weight, vitamin A supplements, if given a worm infestation drug (deworming), and an episode of diarrhea 2 weeks before the survey. The mothers' age, body mass index, and education level were analyzed at the mother's level, while the type of residence (rural or urban), type of toilet (improved or unimproved), sources of water (improved or unimproved), and time spent on getting water were analyzed as

Key Message
• Any form of malnutrition in children aged from 0 to 23 months is an alarming threat since its consequences may persist even in adults and they cannot be reversed.
• Gender, age, birth weight, mothers' BMI and education level, and type of toilet facility available to the household were all risk factors for underweight in children under the age of 2 years.
• Nutrition interventions such as growth monitoring, nutrition counseling, and nutrition education for parents/ caregivers are critical to ensuring that all children gain the appropriate amount of weight. household factors. Furthermore, child feeding practices like the extent of exclusive breastfeeding, continuing breastfeeding for 1 or 2 years, minimum dietary diversity, and minimum meal frequency were analyzed. The households were assessed against an improved toilet, which was supposed to be a toilet with a flush or pour-flush toilet connected to a piped sewer system, septic tank, pit latrine, ventilated improved pit (VIP) latrine, and pit latrine with a slab or composting toilet.
The independent variables at the individual level were assessed through self-reports of the child's mother during interviews. The children's receiving of vitamin A and deworming drugs was assessed by recalling the children's mothers at 6 months. Assessment of the onset of diarrhea by recalling the child's mother for 14 days.
Assessment of child feeding practices including breastfeeding was done through 24-h memories of the mother. In addition, sociodemographic characteristics like age and education level were mainly self-reported by the mother while environmental factors like type of water source and toilet facility were observed by the interviewer during the interview.

| Data analysis
During data analysis, the Statistical Package for Social Science (SPSS) version 25 was used. Initially, the recorded data were cleaned, transformed, and recorded in the recommended format as per this study.
The prevalence was calculated for all categorical data. The outcome variable for this study was underweight, which was recorded as binomial data with "1" coded as normal weight and "0" as underweight.
The association between dependent and selected determinant factors was done using Chi-square. Bivariate and multivariate logistic regression was done to determine the odds of determinant variables showing significant association with dependent variables. The backward elimination process was selected during multivariate analysis to assess factors that were significantly associated with the study outcome using a 5% significance level. To avoid or minimize statistical error, multicollinearity was tested. The odds ratios with 95% CIs were calculated in order to assess the adjusted risk of independent variables, and those with p < .05 were retained in the final model.).
Statistical significance was defined as a p-value of less than 0.05.

| Social demographic characteristics of study's participants
The age group was equally represented, with a slight increase observed for 12-17 months (Table 1). About 17.6% of children experienced diarrhea in 2 weeks before the survey. The majority of children (93.4%) were born with an average or above-average weight. Over 50% of the children had not received vitamin A supplements and deworming tablets for 6 months before the survey.

| Infants feeding practices
The result from

| DISCUSS ION
Multivariate analysis found children's age, gender, birth weight, mother's level of education, and BMI, as well as the type of toilet facilities used in the households were all revealed to be significant predictors of underweight in this study.
The low likelihood of female children being underweight found in this study mirrors the findings described previously in Rwanda and South Africa (Lesiapeto et al., 2010;Mukabutera et al., 2016). Female children's reduced risk of being underweight may be due to their low calorie requirements, which can be easily met by typical feeding practices, such as when mothers assure on-demand breastfeeding.
In contrast, other studies conducted in Pakistan, India, Indonesia, Ghana, and Kenya indicated that female children were more likely to be underweight than male children (Kumar et al., 2019;Acquah et al., 2019;Sari et al., 2020 andStalin et al., 2013).
Children in the age group of 18-23 months were significantly more likely to be underweight compared with other groups. This result is in line with a previous study conducted in Ghana, which indicated that children aged 12-23 months had a higher chance of being underweight than children of other age groups (Acquah et al., 2019).
This could be attributed to increased physical activity at this age when children can walk and run, as well as a decrease in mothers' care for these children due to the assumption that they are already grown up. Therefore, more training and counseling for mothers/child caretakers on proper and consistent feeding of all children under the age of 2 years when they attend postnatal clinics is needed to guarantee that children acquire weight (0.5 kg per month) as suggested by WHO. However, this result was different from studies conducted in Uganda and Kenya which show children less than 12 months are more likely to be underweight and stunted compared to older groups (Habaasa, 2015).

Number of children
Furthermore, significantly higher risks of underweight were found for children born with a lower birth weight compared to other children born with an average or higher than average weight. Similar results were reported in Indonesia (Sari et al., 2020), Kenya (Gewa & Yandell, 2012), Pakistan (Kumar et al., 2019), and Nepal (Adhikari et al., 2017). Low birth weight has been linked to a variety of health issues, including infant respiratory distress syndrome and neonatal deaths. To ensure proper weight gain throughout pregnancy and the delivery of healthy and appropriate-weight babies, all pregnant women should receive counseling, which should include early attendance at prenatal clinics, good nutrition (dietary diversity), and regular intake of prenatal vitamins and minerals, such as folic acid and iron supplements.
Moreover, the likelihood of being underweight was higher for children who were born with mothers who had a BMI lower than 18.5. The significant correlation between underweight and the mother's BMI was also reported in the studies conducted in Ethiopia, Ghana, Rwanda, and Nepal (Acquah et al., 2019;Adhikari et al., 2017;Mukabutera et al., 2016;Yisak et al., 2015). The physiologic effects of maternal malnutrition during lactation probably have an impact on milk secretion and a child's weight gain. Therefore, interventions aimed at improving maternal nutrition may be useful in reducing childhood malnutrition.
Likewise, a mother's education emerged as a significant factor that could predict being underweight for children surveyed.
The increased risk of being underweight for children belonging to mothers with low education was also reported in the studies conducted in Rwanda (Mukabutera et al., 2016), South Africa (Lesiapeto et al., 2010), and Pakistan (Kumar et al., 2019). Mothers with a low level of education may be missing out on some essential information about infant and young child feeding practices, resulting in poor feeding and weight gain for their children. Thus, nutrition education should be organized for mothers/care givers during postnatal visits, depending on their level of education, or giving priority to loweducated mothers/care givers. generalization. However, the cross-sectional structure of the study made it impossible to establish a causal effect relationship between predators and the variable of interest (underweight). Recalling bias was also observed in this study when caregivers/parents were required to provide some information like feeding practices. It is advised that future large studies take into account the identified limitations.

| CON CLUS ION
The child's age, gender, birth weight, mother's level of education, and BMI, as well as the type of toilet facilities utilized in the households were all revealed to be significant predictors of underweight in this study. Specific nutrition and health interventions are encouraged to ensure recommended weight gain and prevent the underweight burden for this age group. As part of interventions, regular growth monitoring, nutrition counseling, and nutrition education are essential to all parents/caregivers with children under 5 years of age when visiting postnatal clinics.

ACK N OWLED G M ENTS
The authors are indebted to the National Demographic Survey for providing the data. Also, the authors acknowledge Blanka Thobias from the University of Dar es Salaam, Department of Statistics, Stanislaus Henry from Ifakara Health Institute, and Adam Hancy from Tanzania Food and Nutrition Center for technical support during data preparation and analysis.

CO N FLI C T O F I NTE R E S T
The authors declare no conflict of interest.

E TH I C S A PPROVA L A N D CO N S E NT TO PA RTI CI PATE
The permission to do this study was given by the demographic and health surveys (DHS) program.

DATA AVA I L A B I L I T Y S TAT E M E N T
Data for this study are available upon request from the Demographic and Health Survey (DHS) portal (www.dhspr ogram.com).