Background
The malnutrition of children includes undernutrition, over-nutrition and micronutrient deficiency. Of them, undernutrition consists of three indices of stunting, underweight and wasting. In particular, stunting and wasting reflect the chronic or acute undernutrition of children, and underweight reveals the current undernutrition status, but cannot differentiate near-term or long-term undernutrition [
1]. Different forms undernutrition may coexist in children. Preschool children are at a critical period of growth and development, and undernutrition occurring at this period may cause irreversible near-term and long-term effects on the health of children. Such effects include delayed physical and cognitional development [
2‐
4], which even increase the risks of infection, death, hypertension, diabetes and other chronic diseases at adulthood [
5].
About 149 million children under 5 years of age suffered stunting and about 49 million children had wasting in 2018 according to data from United Nations Children's Fund (UNICEF) and World Health Organization (WHO) [
6]. Undernutrition of children is a major public health problem in developing countries, especially Africa and Southeast Asia. China is a developing country in East Asia. With the rapid socioeconomic development in the past 30 years, the significant increase in average disposable income, the optimization of dietary structure, the improvement of caregivers education level and the medical and health services, the nutrition status of children has been significantly improved [
5,
7]. Nationwide nutrition surveys in China show that the prevalence of stunting and underweight among children under 5 years of age between 1990 and 2010 dropped from 33.1% to 9.9% and from 13.7% to 3.6% respectively, but were still up to 20.3% and 8.0% respectively in rural China [
5,
7].
In China, the vast majority of poor areas are concentrated in the rural areas of the central and western provinces. Hunan province with medium economic development is located in central China, and the administrative region includes 123 districts/counties in 14 cities. Hunan is dominated by rural population, accounting for 65.1% [
8]. Hunan is a multiracial province and is dwelt by 9.5% of minorities, including Miao, Tujia, and Dong. In rural Hunan, the economic development is relatively poor, and the caregivers have low education level and deficient nutritional knowledge, and many children receive unscientific feeding and suffer from undernutrition [
9,
10]. A cross-sectional study conducted in 2009 showed that the prevalence of stunting and underweight among children aged 0-7 years in rural Hunan were 16.6% and 7.8%, respectively [
11], which were obviously higher than the national average in 2010. Undernutrition of children can be caused by many factors. A number of observational studies show that poor socioeconomic development, inappropriate complementary feeding practices, household food insecurity, diseases of children (e.g. recurrent respiratory infections and diarrhea), inadequate maternal nutritional status, low education level of caregivers, and children left behind by internal migration are all associated with the undernutrition of children [
12‐
17].
To further improve the nutrition status of children in poor rural areas, National Health Commission of China extensively implemented children nutrition improvement projects in poor rural areas including Hunan province since 2012, including food supplements and nutrition education [
18]. So far, children nutrition improvement projects have been implemented in rural areas of Hunan for eight years. Hence, previous epidemiological investigations are already unable to reflect the current undernutrition levels of children in rural Hunan. Though several children undernutrition investigations have been conducted in rural Hunan recently, the investigated age ranges are narrow and concentrated on under age of 3 years [
19‐
21]. In particular, relevant research on preschool children is insufficient [
22].
In the new era, systematic study on the undernutrition of children under 6 years of age in rural areas, and discovery of key associated factors are critical for prevention and treatment of undernutrition among children in rural areas. Hence, in this study, a community-based cross-sectional survey was conducted to clarify the status and associated factors of undernutrition among children under 6 years of age in rural Hunan. Some targeted interventions were proposed to improve the nutrition status of rural children.
Materials and methods
Subjects
The subjects were children under 6 years of age (0 to 71 months) and their caregivers from rural Hunan investigated between August and November 2019. The sample size was determined according to relevant equations for cross-sectional studies [
23]. Since the stunting prevalence among rural children was estimated to be 16 %[
11], the size of a test α was 0.05, permissible error
d was 0.10, the designed effect of complex samples was 2 and the non-response rate was 20%, the final sample size was determined to be 5040 (= 2100×2× 1.2).
Subjects were selected by multistage stratified cluster sampling. In China, one province consists of several cities, and one city consists of several districts and several counties (districts and counties are urban and rural, respectively); one county contains several towns, and one town has several villages [
22]. The 14 cities in Hunan were divided by economic development into three levels: high, moderate and low. Then 2 cities from each economic level, 2 counties from each selected city, 2 towns from each selected county, and 3 villages from each selected town were randomly selected. From each village, all eligible children were included into our subjects. Totally, 5529 children from 72 villages covering 24 towns in 12 counties were involved.
Data collection
This study consisted of a questionnaire survey and anthropometric measurements. The questionnaire included children’s factors (gender, age, birth weight, preterm birth, left-behind children, only child, passive smoking, regular physical examination), maternal gestational factors (age at delivery, gestational gain weight, moderate/severe anemia, pregnancy comorbidity), and factors of caregivers and family (type of caregivers, ethnicity, education level, occupation, family size, family income, family food expenditure). All children received anthropometric measurements, including length/height, and weight.
Definition of variables
Birth weight referred to the infant’s net weight within 1 hour of birth, and did not include any wear or wraps, which can be obtained from the child’s vaccination certificate or medical certificate of birth. If there was no vaccination certificate or medical certificate of birth, the birth weight of the child was obtained from the recalling by the caregivers. The birth weight <2500 g, 2500-3999 g, and ≥ 4000 g were considered as low birth weight, normal birth weight, and macrosomia, respectively. Birth at <37 gestational weeks was regarded as premature birth. Left-behind children referred to those children whose parents (both or either) worked in other places and did not live together with the children [
22]. Only child was the only child born by one couple, and had no siblings. Passive smoking meant a nonsmoker inhaled at least 15 minutes every day the smoke exhaled by smokers for at least 1 day within 1 week. Maternal gestational weight gain was determined by the final weight of the mother measured in late pregnancy before delivery subtracted by the weight in early pregnanc y[
24] and was divided into four groups of <10.00, 10.00-14.99, 15.00-19.99, and ≥20.00 kg. Maternal moderate/severe anemia was defined as a hemoglobin level <100 g/ L[
25]. The maternal hemoglobin concentration in this study was the concentration in the third trimester of pregnancy. The maternal weights in early pregnancy and in late pregnancy before delivery, and the hemoglobin concentration in the third trimester of pregnancy can be obtained from the clinical medical records of maternal health handbook. If there was no maternal health handbook, the maternal weights and hemoglobin concentration during pregnancy were obtained from the recalling by the caregivers. The maternal pregnancy comorbidities included gestational diabetes mellitus, gestational hypertension, pregnancy associated with cardiac diseases, gestational liver diseases, and thyroid dysfunction. Caregivers were those who took care of the diets, living and personal security of children and were divided into two types: parents, and grandparents/others. Ethnicity of caregivers was divided into Han and minorities. The education level of caregivers was classified into primary school or below, junior high school, senior high school, and college or above. The occupation of caregivers was divided into housework, government agencies staff, business service staff, farmer, and others. Family size was defined as the total number of family members and involved the members with economic relations and joint budget and diets, and was separated into ≤4, 5-6, and ≥7.
Anthropometric measurements
The investigators used unified instruments to measure the length/heights and weights of children according to standardized methods, which were described by the Technical Specification for Children Health Check Service (China Ministry of Health, 2012). The lengths and weights of children aged 0-23 months were measured by using an FSG-25-YE lying-form infants and young children precision medical examination meter (Shanghai Betterren Medical Tech Co., Ltd.). The heights and weights of children aged 24-71 months were measured using an HX-200 stadiometer and an HCS-50-RT electronic scale respectively (Liheng Instrumentation LTD., Shanghai, China). The accuracies of instruments for length/heights and weights were 0.1 cm and 0.05 kg, respectively.
Evaluation criteria for children physical development
The commonly-used indices for children physical development are length/height for age, weight for age, weight for length/height, and body mass index (BMI) for age. BMI was calculated using the ratio between a child's weight in kilograms and length/height in meters squared (kg/m
2): BMI = weight (kg)/ height
2 (m
2). A child’s physical development was evaluated using Z-score recommended by WHO: Z score = (analyzed index - median of reference standard)/standard deviation of reference standard. The WHO Child Growth Standards involve two age groups: 0-5 years (0-60 months) and 5-19 years (61-228 months), which are 2006 Child Growth Standar d[
26] and 2007 Child Growth Standar d[
27]. Hence, the physical development of children was evaluated according to the two age groups above.
(1)
Children aged 0-60 months: length/height for age z score (HAZ), weight for age z score (WAZ) and weight for length/height z score (WHZ) were calculated according to WHO 2006 Child Growth Standard. HAZ <-2, WAZ <-2 and WHZ <-2 were defined as stunting, underweight, and wasting respectively.
(2)
Children aged 61-71 months: HAZ, WAZ, and BMI for age z score (BMIZ) were calculated according to WHO 2007 Child Growth Standard. HAZ <-2, WAZ <-2 and BMIZ <-2 were defined as stunting, underweight, and wasting respectively.
Quality control
The investigators were the child health care doctors selected from the county-level maternal and child health care hospitals of the corresponding counties. The investigators conducted a face-to- face interview with children’s caregivers. Prior to the survey, all the investigators were trained unifiedly, and only the qualified ones were allowed to take part in on-site survey. The instruments were calibrated before and during investigations. The physique measuring staff measured the length/height and weight of children in strict accordance with the specifications of the instruments. During the survey, all copies of the questionnaire were checked by a quality controller. Each copy should be filled in in a complete and standard way. Any illogical or missed response should be corrected in time. Data were double-inputted on Epidata 3.1 and tested in terms of consistency. For any inconsistent data, the original copy should be checked to ensure the high quality of any inputted data.
Statistical analysis
HAZ, WAZ, WHZ and BMIZ were computed using WHO anthropometric macros in SPSS (igrowup_SPSS and WHO2007_SPSS) [
28,
29], and statistical analyses were conducted on SPSS 25.0 (IBM, Chicago, IL, USA). Categorical data was statistically described as proportion or rate. The prevalence of stunting, underweight and wasting among children with different characteristics was compared by Chi-square test. With undernutrition status (stunting, underweight, wasting) as dependent variables (No=0, Yes=1), all 19 factors related to the characteristics of children, mothers, caregivers and families were used as independent variables, and multivariate logistic regression models were developed to identify the associated factors of children’s undernutrition. Variables were selected using a backward selection method. Multivariate logistic regression models were developed separately for each undernutrition status: stunting, underweight, and wasting. The strength of association between significant variables and undernutrition was evaluated by using odds ratios (ORs) with 95% confidence interval (CI). All statistical tests were two-tailed, and the significant level was
P<0.05
.
Ethics approval and consent to participate
The study protocol was approved by the Ethics Committee of Hunan Provincial Maternal and Child Health Care Hospital (No.2019-S036). The study was conducted in accordance with the Declaration of Helsinki. Written informed consents were obtained from all the caregivers of children involved in this study.
Limitations
This cross-sectional study has some limitations. First, the relationship between investigated factors and undernutrition is statistical association, rather than causality. Second, some data about the birth weights of children and the maternal gestational weight gain were acquired from the recalling of caregivers, which inevitably resulted in recall bias. To reduce the recall bias, the clinical medical records of child’s vaccination certificate, medical certificate of birth, and maternal health handbook should be taken as the standard, and the subjective recall of the caregivers should be avoided as much as possible. Nonetheless, this large-size epidemiological study involves 5529 children randomly selected from 72 villages across 24 towns in 12 counties of Hunan, and covers the whole preschool age group. Hence, our findings reflect the undernutrition statuses and associated factors of children (age <6 years) in rural Hunan and will help health administrations to lower undernutrition-caused burdens in rural areas.
Conclusions
The prevalence of stunting, underweight and wasting is low among rural children under age of 6 years in Hunan. Undernutrition of children in this region is affected by birth weight, maternal gestational weight gain, ethnicity of caregivers, education level of caregivers, family size, and family food expenditure. Attention must be focused on strengthening the gestational care and reasonable diet of mothers, and on avoiding nutritional deficiency during pregnancy, which will reduce the occurrence of low birth weight. The local economic development and the education level of caregivers need to be further improved, especially for minorities.
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