Intervention Study to Improve Meal Habit, Sleep Habit, Circadian Typology And School Marks in Japanese Elementary School Students

In accordance with the 24 hours commercialization society which is rapidly going on in current Japanese society which gives children new environmental situations as zeitgebers. Convenient sores are very common in Japanese society and they count more than 20 shops in a small society with 300,000 population, Kochi city for example and smart phones distribute to 98% of junior high school students affiliated to Faculty of Education, Kochi University. Such current situation means that clear light-dark cycles and meals regularity on the times of day tend to disappear for the entrainment of their circadian clocks. According to such environments to children, night activity is supposed to be in progress and also lead to short night sleep hours due to late bedtime and early get-up time because of school and shifting to evening-typed life.

Due to the circumstances for Japanese children, some intervention program is needed for promotion of physical and mental health of Japanese children. Mental health has strong links to circadian typology: lower mental health like as depression can be associated with evening-typed life ^{1, 2, 3, 4, 5, 6, 7}. Because the circadian typology links to mental health, some intervention might be effective for preventing some mental problems in children ⁸. However, such intervention studies for small children attending elementary school or younger are limited to a few ones.

Quach et al. ⁹ reported the intervention project called “Sleep Well Be Well”. This project included individual consultations for families of children aged 5-6 years who had night sleep problems on screening. Gruber et al. ¹⁰ reported a project called “Sleep for Success” to improve sleep health and academic achievement. This project was a whole-school intervention involving sleep education for children, staff and parents. The participants of this project were children aged 7-11 years. This project used objective and subjective measurements of sleep. Sleep duration was elongated, sleep efficiency was improved and sleep latency was shorten due to the intervention. Another effective intervention program called “ACES” was developed for sleep health of adolescents and younger children ¹¹. Participants of 9-10 years were chosen because of no daytime naps already in this age ¹².

However, there have been only a few studies on an intervention study including breakfast intervention (recommendation of taking protein resources) to improve academic achievement together with elongation of sleep hours for small children attending elementary schools so far. This study challenges to promote the academic mark and sleep habits of small children attending a model elementary school in Japan.

The intervention program for a half year seems to be effective for elementary school students to take better mark in academic achievements especially on mathematics through shifting them to “morning-typed” life. How does the morning-typed life link to better academic achievement in elementary school students? Three hypotheses would be possible as follows.

At first, sufficient REM sleep at the morning time zone can promote the fixation of new memories and also memory consolidation in school life. For sufficient REM sleep taken, morning-typed life is suitable, because two conditions for sufficient REM sleep to be taken are critical. The first condition is that a long sleep hours is needed before the long REM in the morning time zone like as 4-6 oclock. That means we need early bed time. Another condition is that there would be a “circadian time gate” which will open in the early morning zone for long REM sleep to occur. So, we have no choice and do morning-typed life.

Second, morning-typed life can promote better mental health ^{1, 2, 3, 4, 5, 6, 7}. Children who are morning-typed can challenge new academic contents in school with higher mental powers.

Third, morning-typed life can link to taking nutritionally rich breakfast, especially including protein resources like as (fermented) soy beans, eggs, fishes, and meats. The hypothesis is that the three conditions are needed for the phase advance of the circadian clocks of students. The first condition is that children should take protein sources of tryptophan and vitamin B6 at breakfast. The second one is that they should be exposed to sunlight after taking the nutritionally rich breakfast for serotonin synthesis. The third one is that they should be exposed to low temperature lights from night lighting for sufficient synthesis, at night, of melatonin from serotonin. These hormones work as natural anti-depression drugs (serotonin) and natural sleeping pills (melatonin) and function as inner zeitgebers for their circadian clock. They can finally make students more-morning typed and improve their mental health. The Higher serotonin level in daytime can be, the higher children’s concentration on academic work at school is, leading to higher academic marks. Several studies support the hypothesis ^{16, 17, 18, 19, 20}.

At least for the students who had been evening-typed, the intervention on meal habits may be effective for longer sleep hours and improved school achievement marking.

Thanks should be due to all the participants in this study. The following financial supports have been given to this study: 1) Fund from J-Milk „Meals and Education‟ (To T. Harada: 2013-2014), 2) Fund from J-Mild „Research Study to Promote Health by Milk and related foods‟ (To T. Harada: 2016-2017) and 3) Funds from Japan Society for the Promotion of Science (JSPS Grant Number JP 16K01871, 2016-2019: To H. Takeuchi).

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