Nine-year Longitudinal Study Of Obesity In Japanese Young Children

Abstract

PURPOSE: Childhood obesity is increasing worldwide. Tracking, or the tendency for an individual to maintain his/her disease risk factor rank level relative to his/her peers through time, leading to adolescence and adult obesity is observed even in early childhood. Childhood obesity is associated with increased risk of mortality due to cardiovascular diseases in adulthood, independent of adult weight. Therefore, intervention, and prevention of obesity in young children is important in reducing the risks of obesity and cardiovascular disease in adulthood. However, little is known about the process and tracking of obesity during the years of young childhood because of a lack of longitudinal studies. Consequently, prevention and treatment of obesity in the young childhood has made little progress. The purpose of this study is to investigate the trends in degree and tracking of obesity in young children over nine years. METHODS: The subjects were 58 young children (22 boys and 36 girls). They were followed up for height, weight, and obesity index from 3 to 11 years old. Obesity index ((actual weight - standard weight)/standard weight×100) was calculated using the standard weight for Japanese children, which was determined according to the formula: Male y=1.83×10-3x2-0.071x+4.43, female y=2.34×10-3x2-0.157x+7.71 (y: standard weight, x: height). Obese was defined as having an obesity index of more than +15%. Pearson’s correlation coefficients and χ2 test were used to estimate the effects of age on frequency trend and tracking of obesity. Statistical significance was p<0.05. RESULTS: The prevalence of obesity was 17.2% (n=10) in 3-year-old children and 20.7% (n=12) in the same children at 11-years-old. There were no age-related differences in frequency of obesity. The obesity index at 3-years old was significantly correlated with that at 4-years-old (r=0.861), 5-years-old (r=0.774), 8-years-old (r=0.630), 9-years-old (r=0.548), 10-years-old (r=0.559), 11-years-old (r=0.512). Among 10 young children who were obese at 3-years-old, 3 showed tracking of obesity from 11-years-old. CONCLUSIONS: The status of many obese young children is likely to track, but the chance of a decrease in obesity over nine years is not small in young childhood.