Children's physical development is affected by inheritance, nutrition, environment, exercise and living conditions, etc. Nutrition plays a particularly important role. With the rapid development of economic improvement and a changing natural environment, incidence of stunting and STH infections has also declined. Although the World Health Organization had estimated that an overall prevalence of stunting has fallen in developing countries from 47% in 1980 to 33% in 2000, stunting in school-age pupils is common in developing countries with the stunting prevalence being higher in primary schools. Malnutrition is still a major public health problem in poor areas in developing countries[14, 15]. In these study areas, health knowledge and health status of pupils had improved considerably, but our results indicate in the rural areas, prevalence of stunting in school-age pupils was 26.5%. School-aged pupils had the highest prevalence and intensity of STH infections. Stunting represents a chronic state of nutritional stress. That is to say, these pupils had long history of lack of nutrition, or they were infected by some other disease.
To evaluate children's growth and development needs a comparable reference value. WHO recommends Z-score as the best method. It is calculated according to weight and height and reflects children's growth and development. It compares the distribution of Z-score of the tested group with that of the reference group, then to find the tested group's nutrition conditions. Z-score can evaluate children's general nutrition conditions. In this study, mean HAZ data were all negative, which illustrated the fact that the nutritional condition in the tested group had a significant difference compared with WHO standard. In addition, HAZ value also reflects the whole lower economic level and human body exposesed to poor conditions. In this study, STH moderate-to-heavy intensity infections influenced children's growth and development, and there is significant difference between its mean HAZ data and that of non-infection group (p < 0.05).
The present data showed that STH moderate-to-heavy intensity infections are important risk factors for stunting. STH infections are widely distributed throughout the tropics and subtropics. STH infections in people remains a worldwide public-health threat for as long as poverty persists in the developing world. The STH infections are one of the world's most important causes of physical and intellectual growth retardation. Previous studies had found Trichuris, Ascaris or co-infection were all associated with stunting[8, 17]. Soil-transmitted helminths lead to nutritional loss. Mechanisms by which STH infections can lead to stunting in pupils including decreased appetite and food intake, depletion and impaired absorption of micronutrients and anaemia. The blood loss which is associated with Trichuris infection can lead to chronic dysentery, iron deficiency, iron deficiency anaemia and poor growth rate. Well-nourished children, who have better nutrient reserves, are thought to be less vulnerable to the adverse effects of parasitic infections. Previous studies have showed growth improvements of pre-school children after anthelmintic treatment[19, 20]. Longitudinal studies have also demonstrated that stunted children continue to deviate from growth standards as they get older. Our results suggest that the risk of stunting continues to grow as age increses. So, treatment of helminth infections in school-age children may improve growth in areas where stunting and helminth infections are prevalent.
In this study, anaemia was also found to be associated with stunting and was a risk factor for stunting. It is stated by WHO that anaemia remains one of the most intractable public health problems in Africa, contributing to a quarter of Africa's nutrition-related Disability Adjusted Life Years (DALYs) lost. Anaemia in children can be caused by iron deficiency and by health factors such as parasitic infection. In this study, 135 pupils were anaemic (HB < 12 g/dl) with a prevalence 13.1%. Among anaemic pupils, the prevalence of stunting was 40.7%. the difference was statistically significant (p < 0.05).
In this study, it is clear that mother's education level was an important risk factor for children's growth and development. Maternal education has been previously found to be an important risk factor for childhood malnutrition[24, 25]. Thus, if mothers have a better education and knowledge on health care, they may have better knowledge of proper health and nutrition behaviours for their families. So, health and nutrition educational interventions targeted to mothers and pupils are needed.