Abstract
Purpose : Based on the results of a cohort study conducted in Tachikawa City, Tokyo in 1992 on 3-year-old children and the follow-up study in 1996 on 6-year-old children, we performed this study to clarify the characteristics of health status and lifestyle. We examined the relationship between changes over time and social factors in children who were underweight or overweight when entering the first grade of elementary school to obtain information to prevent lifestyle related disease.
Subjects : The first study was conducted in 1992 using 1286 3-year-old children in Tachikawa City, Tokyo who received a regular health checkup at the Tachikawa Health Center. Of these subjects, 1148 (89.3%) responded. The follow-up study was conducted on 1360 6-year-old children who entered elementary school in Tachikawa and other cities in 1996. Of these subjects, 591 (40.5%) responded. Our analysis was based on 384 children for whom data on height and weight were available and who responded to both studies.
Methods : We calculated the body mass index (BMI) from heights and weights measured at the time of both studies and examined the relationship between BMI measured at ages 3 and 6. The children were divided into three groups based on BMI : the underweight group (BMI less than 14), the normal weight group (BMI from 14 to less than 18), and the overweight group (BMI of 18 or more). We studied the relationship between lifestyle and social factors based on the parents' responses to the questionnaire on health and lifestyle and assessed the relationship between the lifestyles of children at ages 3 and 6.
Results : (1) There were 31 children (8.1%) in the overweight group and 46 children (12.0%) in the underweight group among children entering the first grade of elementary school. The correlation between BMI at ages 3 and 6 was very high. However, both percentages of the groups increased from 5.7% to 8.1% in the overweight group and from 2.3% to 12.0% in the underweight group during the 3-year interval. (2) Few underweight children evaluated their health status as “very good” compared with overweight children. Moreover, compared to the normal group, more children in the overweight group ate at a fast speed, ate breakfast alone, did not have bread or milk at breakfast, and did not have snacks at a set time. The percentage of children who were an onlychild or who did not have a father was higher in the overweight group. Not many children in the underweight group had breakfast by themselves but many had a traditional Japanese breakfast of rice and miso soup, had dinner with their grandmothers, slept longer, and went to sleep later. Children in the underweight group tended not to have grandmothers who lived with them or not to have mothers who were full-time housewives. (3) The correlation between lifestyle at ages 3 and 6 was very high. Furthermore, correlations were observed among contents of breakfast, eating with others, eating time of snacks, living arrangement with grandmothers and work status of mothers.
Conclusions : The percentages of children who were either underweight or overweight upon entering elementary school were higher than those in the 3-year-old children. However, a strong correlation between BMI at ages 3 and 6 and lifestyles at ages 3 and 6 was observed. These results suggest that intervention in this period may be effective to establish a healthy lifestyle for children. Moreover, intervention must be considered depending on whether or not the grandmother lives with the children or if the mother stays at home. Since more than 10% of first grades were underweight, special characteristics related to health status, lifestyle and social factors in underweight children should be further examined. The relationship between the health status and lifestyle of underweight children should be evaluated over the long-term.
