Assessment of Japanese healthy children’s nutritional status using Waterlow classification ()
1. INTRODUCTION
Malnutrition is a state in which a deficiency or excess of nutrients may increase morbidity or mortality. Several investigators have reported on malnutrition and a risk of under-nutrition such as wasted or stunted condition or overweight in both hospitalized general patients [1-3] and those with specific disorders [4,5]. Since undernutrition and disease interact with each other adversely, adequate and prompt nutritional supports are required. There are several methods for evaluating a patient’s nutritional status, including anthropometric measurements, dietary intake, biochemical parameters, and resting energy expenditure [6-8]. In hospitalized children, there is a good chance to use all of these measures; however, in healthy children, especially as a large cohort, it is difficult to perform these methods, except for anthropometric measures. Among several anthropometric measures, height-for-age (H/A) and weight-for-height (W/H) have been widely used in various clinical settings. H/A and W/H were first presented by Gomez et al. in 1956 [9] and by Waterlow in 1972 [10], respectively. Later, Waterlow put the two measures together and defined H/A as an indicator for chronic nutritional status and W/H as an indicator for acute nutritional status [11]. Therefore, both measures are often called “Waterlow classification” in the literature. Waterlow classification has been widely used in hospitalized children for evaluating nutritional status on admission and to track changes over time during hospitalization [1,2,5,12]. However, there are very few large-scale studies on the H/A and W/H scores in healthy children. The reference values are potentially important for adequate assessment of sick children in comparison with a healthy population. Therefore, in this study, we tried to determine the reference values and an incidence of malnutrition among healthy children at 3 - 17 years of age in a large cohort of more than 7000 participants.
2. MATERIAL AND METHODS
2.1. Participants
To gain permission for the use of data obtained at an annual health check, we first sent a letter to 30 randomly selected principals of senior high schools, junior high schools, elementary schools, or kindergartens in Nara city between 2008 and 2010. Due to the restrictions on the use of personal information, we obtained consent from approximately 60% of the principals. We went to those schools to collect the data on a paper basis and in total enrolled 7517 healthy children (3747 boys and 3770 girls) aged 3 to 17 years old in this study (Table 1). Health checks were performed in April or May every year and were done by school teachers or school nurses who were well trained. Body weight was measured to the nearest 0.1 kg, and height was measured to the nearest 0.1 cm. At the same time, we recorded each subject’s birth date to calculate respective standard weight and height.
2.2. Waterlow Classification
The Waterlow classification measures of W/H and H/A are calculated according to the following formula: W/H= [observed weight/standard weight (for the same age and height and sex)] × 100, and H/A= [observed height/standard height (for same age and sex)] × 100 [11]. We used the official Japanese children’s anthropometric data for children age 5 and over published by the Ministry of Education, Culture, Sports, Science and Technology [13], and for those age 4 and under published by the Ministry of Health, Labor and Welfare [14], as the standard weight and height. The criteria for the diagnosis of
malnutrition were for W/H, <70% severe, 70% - 80% moderate, 81% - 90% mild under-nutrition, and ≥110% overweight, and for H/A, <85% severe, 85% - 89% moderate, and 90% - 95% mild under-nutrition. Differences between the prevalence of malnutrition among different age groups were examined using a population proportion test (SPSS ver.19). p values less than 0.05 were considered significant.
3. RESULTS
3.1. Prevalence of Children at Risk for Malnutrition
The prevalence of children at risk for malnutrition according to Waterlow classification is summarized in Table 2. Among our study subjects, 1513 (20.1%) and 624 (8.3%) children were found to be at some grade of malnutrition based on the evaluation of W/H and H/A, respectively. Of the former 1513 children, 10 (0.1%), 177 (2.4%), and 1326 (17.6%) children were at levels of severe, moderate, and mild under-nutrition, respectively. On the other hand, of the latter 624 children, none, 24 (0.3%), and 600 (8.0%) children were at levels of severe, moderate, and mild under-nutrition, respectively. Eight hundred and nine (10.8%) children were assessed as being overweight.
3.2. Change in the Prevalence of Children at Risk for Malnutrition with Age
Figure 1 indicates the prevalence of children at risk for under-nutrition with age. The prevalence at any grades of under-nutrition by W/H tended to reach their peaks at the age of 12 in both sexes. Actually, 121 (33.8%) boys and 141 (36.9%) girls were found to be under-nourished at 12 years old. When we compared the prevalence of under-nutrition at 12 years old with other ages, the differences were statistically significant. In the measure of H/A, the prevalence of under-nutrition was highest at the age of 11 years for boys (30; 16.3%) and 10 years for girls (25; 16.7%).