The height of the Japanese people has increased dramatically since the end of the Second World War. This increase in size is commonly attributed to growth during the period when children attend school (approximately age 6-17).
However, in this paper we reviewed Japanese school health statistics since 1900, and concluded that the increase in the height was not a result of the growth from age 6-17, but instead depended on growth occuring in early childhood (age 0-6).
Furthermore, total growth from age 6-17 has consistently decreased since the end of WWII, while the height of 6 year-olds has increased. There is a clear inverse relationship between the two (r=－0.951 (male) and r=－0.987 (female)); the more growth until age 6, the less growth from age 6-17.

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The purpose of this study was to examine the causal structure between life styles and mental health of elementary-school children. Using surveys on actual conditions of 540 elementary-school children in the fourth through the sixth grades, we analyzed the causal relations between life styles and mental health by applying a model developed through structural equation modeling. The model exhibited relatively good conformity. Life-style latent/unobserved variables including　“cleanliness/neatness,”　“eating lone,”　“feeling of sleeplessness,”　and　“late bedtime”　directly or indirectly influenced mental health latent/unobserved variables including　“friendship/family relations,”　“uneasy feelings,”　“physical condition,”　and　“irritation.” “Feeling of sleeplessness”　has a large, direct influence on　“uneasy feelings,”　“physical condition,”　and “irritation,”　so it remarkably influences mental health. Furthermore,　“late bedtime”　indirectly influences “uneasy feelings”　via　“feeling of sleeplessness”　more than it directly influences it. The importance of reviewing sleep-related habits and reducing　“feelings of sleeplessness”　was suggested for enhancing the mental health of elementary-school children.

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