Journal of Sleep and Sleep Disorder Research
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Research Article | Open Access
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  • Intervention study to improve meal habit, sleep habit, circadian typology and school marks in Japanese elementary school students

    Hitomi Takeuchi 1     Mizuka Nakao 2     Wataru Kurose 2     Takahiro Kawada 3     Teruki Noji 3     Miyo Nakade 4     Fujiko Tsuji 1     Mirada Krejci 5     Tetsuo Harada 1      

    1Laboratory of Environmental Physiology, Graduate School of Integrated Arts and Sciences, Kochi University

    2A Public Elementary School, Kochi Prefecture

    3Regional Collaboration Center, Kochi University

    4Department of Nutrition Management, Faculty of Health and Nutrition, Tokai-Gakuen University

    5Palestra University, Physical Education and Sports

    Abstract

    Purpose:

    An intervention program was performed to improve meal habit, sleep habit and academic marks at school. This program was called “Super Meal Educational Program” which was supported by Japanese Ministry of Arts, Sports, Sciences and Education. Effects of the intervention were evaluated by comparing an integrated questionnaire study held both before and after the intervention of a half year.

    Method:

    The intervention program consisted of a lecture on sleep health and diurnal rhythms on children by an university professor, a series of lectures and practical classes by elementary school teachers on foods which can be collected nearby, and also practical courses as excursions to learn traditional meals and several foods resources which are products nearby. Integrated questionnaire study and also government official academic achievement test were performed before and after the intervention for 6 months in May to November, 2015. An integrated questionnaire was administrated to elementary school students of grades 1 to 6 (7-12 years old). For the younger students aged 6-9 years old, parents (mostly mothers) answered the questionnaire instead of their children. The participants consisted of 40 to 55 students in each grade from the first to the six one of the elementary school. The rate of answer to the questionnaire was more than 95% and the number of data used for statistic analysis was 295 before and 286 after the intervention. The integrated questionnaire included questions on the diurnal type scale (DTS), sleep habits, meal habits, and other questions on their environments and life-habits.

    Result:

    In the histogram on distribution of the diurnal type scale scores (DTS) before intervention, the students which occupied 25% evening-typed significantly shifted to more morning-typed ones after the intervention (p<0.001). There was significantly negative correlation between DTS scores before intervention and the amount of increased change in DTS during the intervention period (r=-390, r<0.001). For all students in the elementary school, there were no significant changes in sleep quality, bedtime in weekdays, wake up time and sleep hours before and after the intervention period. There was negative correlation between sleep hours in weekday before intervention and increased amount in sleep hours before and after that (r=-0.545, p<0.001). The longer the sleep hours were shifted longer during intervention, the better the academic achievement mark of mathematics was after the intervention (students in the second, third and fifth grades: p=0.001).

    Conclusion:

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

    Received 24 Dec 2016; Accepted 28 Mar 2017; Published 21 Jul 2017;

    Academic Editor:Ravi Gupta, Department of Psychiatry & Sleep Medicine Himalayan Institute of Medical Sciences

    Checked for plagiarism: Yes

    Review by: Single-blind

    Copyright©  2017 Tetsuo Harada, et al.

    License
    Creative Commons License    This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

    Competing interests

    The authors have declared that no competing interests exist.

    Citation:

    Hitomi Takeuchi, Mizuka Nakao, Wataru Kurose, Takahiro Kawada, Teruki Noji et al. (2017) Intervention study to improve meal habit, sleep habit, circadian typology and school marks in Japanese elementary school students . Journal of Sleep and Sleep Disorder Research - 1():42-54.
    Download as RIS, BibTeX, Text (Include abstract )
    DOI10.14302/issn.2574-4518.jsdr-16-1413

    Introduction

    The 24 hours commercialization society which is rapidly going on in current Japanese society gives children new environmental situations as zeitgebers. Convenient sores are very common in Japanese society and count more than 20 shops in a small society with 300,000 population, Kochi city for example and smart phones distribute to 98% of students in a junior high school 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 leads to short night sleep hours due to late bedtime and early get-up time because of school and shifting to evening-typed life.

    Thinking of the circumstances of 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 life1, 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 children8. However, such intervention studies for small children attending elementary school or younger are limited only to a few cases.

    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 which was a whole-school intervention involving sleep education for children, staff and parents. The participants of this project were children aged 7-11 years using 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 in adolescents and younger children11. Participants of 9-10 years were chosen because of no daytime naps already in this age12.

    However, there have 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.

    Materials and Methods

    Description of the study participants including number of participants

    The integrated questionnaire and Government Academy Achievement Test held by Japanese Ministry of Education, Arts, Sports, Sciences and Technology were administered twice in May and November in 2015 to all students who attended an elementary school (33ºN, 133ºE) in Kochi Prefecture, Japan. Students of all grades of the 1st to 6th answered the integrated questionnaire, ones in the second, third and 5th grades did it the Government Academy Achievement Test. More than 95% of the students in this school which both of the integrated questionnaire and the Government Academy Achievement Test were administered, answered the both. The number of students who answered the integrated questionnaire consisted of 40-55 in each of the first to the six grades of the elementary school. The integrated questionnaire included, 1) Diurnal type score questionnaire (DTSQ) Torsval and Åkerstedt13 constructed, 2) Questions on sleep habit (bedtime, wake-up time, sleep hours of both weekdays and weekend), 3) Questions on mental health (irritation, anger, out of controlling emotion, depression).

    Study protocol

    The intervention program consisted of a lecture on sleep health and diurnal rhythms on children by an university professor, a series of lectures and practical classes by elementary school teachers on foods which can be collected nearby the elementary school, and also practical courses as excursions to learn traditional meals and several foods resources which are products nearby it (Table 1). The results of two questionnaires which were the almost same could be compared before and after the intervention for a half year by identifying each of participated students one by one using identifying number. However, detailed names were hidden for the analyzers and researchers from ethic view point.

    Table 1. Detailed contents of this intervention program, “Super Meal Educational Program” in accordance with time course.
    14 April 2015: Planting of larval rice into paddy fields in the field of the elementary school (5th grade students)
    20 April 2015: Whole Japan Common Academic Questionnaire Marking Examination in Elementary School Subjects (2nd, 3rd and 5th grade students)
    22 April 2015: Making a specific cubiculum for meals education with teachers and an guest university professor majoring in the meals education.
    20 May 2015: Research class entitled “Welcome to ‘Yamamoto plum restaurant and café’ Chairs with Yamamoto-plum hand-made juice! ” performed by a teachers and handy-capped children
    25 and 26 May 2015: Practical class for making a cooked (only surface) Tuna-meat (“Katsuono-tataki”) (4th grade students
    27 May 2015: A special class for meal education entitled “Making a special and enjoyable menu!” (3rd grade students) in which breakfast recommended- in terms of nutritional components and type of food.
    15-19 June 2016: Campaign week entitled “Let’s finish to eat all food staffs supplied for lunch without foods which were left!”
    26 June 2016: 1st Open Lecture for Meals Education entitled “Meals educations can promote academic achievement (Audiences: teachers and parents, Lecturer: a meals educator)
    3 July 2017: Lecture on green pepper (Japanese name: Shishito) for parents and children
    6 July 2017: A special class for meal education entitled “Let’s think about vegetables which grow currently in the field!” (2nd grade students)
    14 July 2017: A harvest festival for summer vegetables (2nd grade students)
    2nd September 2017: A special lecture by an university professor entitled “Life habits and academic achievements” (5th grade students)
    10 August 2017: A special lecture by an university professor majoring in sleep science and chronobiology entitled (On the correlation between life habits including sleep habits and academic achievements in elementary children (Audience: elementary school teachers)
    14 August 2017: A practical meals education class: Harvest of rice from paddy fields in the elementary school field (5th grade students) in which breakfast recommended- in terms of nutritional components and type of food.
    2 October 2017: A special lecture by an university professor entitled “Meals habit and academic achievement in elementary school students” (Audience: 5th grade students, teachers and parents) in which breakfast recommended- in terms of nutritional components and type of food.
    28 October 2017: A special class for meal education entitled “Ideal meals habit which can be recommended for elementary school students” by an guest university professor (4th grade students) in which breakfast recommended- in terms of nutritional components and type of food.
    2 November 2017: A special lecture for meals education entitled “Results of intervention study and relationship between meals habit and academic achievement of elementary school students” (Audience: teachers and parents) in which breakfast recommended- in terms of nutritional components and type of food.
    18 November 2017: A special lecture of Japanese language course entitled “Think about Japanese culture. Searching on Japanese traditional sweets” by a elementary school teacher (5th grade students)
    20 November 2017: A special practical course for meals education entitled “Let’s pond cooked rice to make cakes (“Omochi-tsuki” in Japanese) (2nd grade students)

    Scales / questionnaires used (including psychometric properties and method of scoring)

    The diurnal type scale (DTS) is the short version of Morningness-Eveningness scale Torsvall and Åkerstedt (1980) originally constructed. The DTS is used to measure an individual’s diurnal preference. Three of the 7 questions included in the DTS pertain to sleep onset timing in the evening, 3 to sleep offset timing in the morning, and 1 to peak timing of activity during the daytime. Each question allows for choice (scored from 1 to 4). The DTS score is the sum of the 7 answers. The minimum possible score is 7 (extreme evening-type), and the maximum possible score is 28 (extreme morning-type). The questionnaire currently used most widely was constructed by Horne and Östberg (1976) and was based on an original questionnaire by Östberg consisting of 14 items which was revised and lengthened to 19 items. Correlations have been examined in M-E scores in the two versions: one by Torsvall and Åkerstedt (1980), the other by Horne and Östberg (1976). High correlation values were seen in junior high students aged 11-15 years (Ishihara, communication, r=0.673-0.762; Pearson’s correlation test: p<0.001), and for 18-25 year old students in occupational and physical therapy training school (Harada unpublished, r=0.736; Pearson’s correlation test: p<0.001). This provides validation of the Japanese version of the Torsvall and Åkerstedt questionnaire.

    Part of the integrated questionnaire used in this study was on sleep habits originally constructed by Harada et al. (1998) which has been used in several papers (Harada et al., 2002; Harada et al., 2004; Takeuchi et al., 2001a; Takeuchi et al., 2001b; Takeuchi et al., 2003; Shinomiya et al., 2004; Kawada et al., 2016). Eleven questions were selected from the questionnaire on sleep habits including sleep quality, sleep hours, regularity of sleep-wake cycles and sleep satisfaction. The regularity and contents of breakfast were examined using those used in several papers (Harada et al., 2007; Nakade et al., 2009, 2012; Wada et al., 2013).

    Japan Wide Academic Achievement Examination for Children in spring and late fall 2015

    Japan Ministry of Education, Science and Technology, Sports and Arts organized a Japan wide examination project to measure academic achievement of elementary schools students of 2nd, 3rd and 5th grades in the 47 prefectures of the whole Japan. In this study, mathematics course and Japanese language course were the subjects for the academic achievement examinations which were held in May and November 2017. In Japan language course examination, 23 questions in total were prepared for interest/will, speaking & listening, writing, reading and language skills (Table 5). The average score of all the questions was calculated as an integrated score as the Japanese language mark shown in figures. In mathematics course examination, 29 questions in total were prepared for way to think, skills, and knowledge (Table 6). The average score of all the questions was calculated as an integrated score as the mathematics mark shown in figures.

    Table 5. Results of academic achievement (Japanese language course) examination scores before and after the intervention
    Japanese language Each scores from several view points Basic and applied ability
    Integrat- ed scores Interest • will Speaking listening &Writing Reading- Language skills Basic Applied ability
    Average thinking expression
    Decision
    2'1 grade before Mean 83.7 78 85.5 72.3 77.5 85.4 87.5 65.2 69.6 60.9
    Desired value 80.4 75 83.3 75.6 76.7 81.4 84.7 60 62.5 57.5
    Japan average 84.8 80.9 86.5 77 77.4 89.1 88.6 66.6 71.8 61.4
    after Mean 78.1 71.3 71.8 72.6 66 90.9 80.6 66 64.1 67.9
    Desired value 78.3 75.6 83.3 73 60.7 91.1 82.4 58.8 55 62.5
    Japan average 81.2 78.6 83.7 78.1 62.2 95.3 85.3 61.9 54.8 68.9
    3rd grade before Mean 75.8 83.2 90.6 78.3 65.4 79.2 76.2 75 64.6 81.9
    Desired value 73.6 77.5 85 75 61.9 77.7 75.3 67 62.5 70
    Japan
    average 74.9 79.1 90.7 73 59.6 81.8 75.8 71.1 65.5 74.8
    after Mean 74.2 67.1 86.1 56.5 64.2 82.5 76.7 63.1 68.7 54.6
    Desired value 69.8 65.6 83.3 55 61.3 76.2 71.4 63 66.7 57.5
    Japan average 73.6 67.7 89.2 55.1 63.2 81.8 75.4 65.9 70.7 58.9
    5'1' grade before Mean 64.8 59.6 59.4 51.9 57.1 71.2 66.6 56.1 71 33.8
    Desired value 67.7 63.8 68.3 57.5 64.4 71.4 68.9 62 75 42.5
    Japan average 70.9 66.9 72.3 60.5 66.5 75.3 71.9 66.1 80.8 44
    after Mean 67.7 74.1 73.7 74.5 62.1 65.4 71.9 48.3 52.1 39.9
    Desired value 68.9 70 73.3 68.3 62.4 70.2 73.3 49 55 40
    Japan average 72.3 73.9 75.1 73.1 66.3 72.8 77 50.7 57.9 39.9

    Table 6. Results of academic achievement (Mathematics course) examination scores before and after the intervention
    Japanese language Each scores from several view points Basic and applied ability
    Integrat- ed scores Interest • will Speaking listening &Writing Reading- Language skills Basic Applied ability
    Average thinking expression
    Decision
    2nd grade before Mean 83.7 78 85.5 72.3 77.5 85.4 87.5 65.2 69.6 60.9
    Desired value 80.4 75 83.3 75.6 76.7 81.4 84.7 60 62.5 57.5
    Japan average 84.8 80.9 86.5 77 77.4 89.1 88.6 66.6 71.8 61.4
    after Mean 78.1 71.3 71.8 72.6 66 90.9 80.6 66 64.1 67.9
    Desired value 78.3 75.6 83.3 73 60.7 91.1 82.4 58.8 55 62.5
    Japan average 81.2 78.6 83.7 78.1 62.2 95.3 85.3 61.9 54.8 68.9
    3'd grade before Mean 75.8 83.2 90.6 78.3 65.4 79.2 76.2 75 64.6 81.9
    Desired value 73.6 77.5 85 75 61.9 77.7 75.3 67 62.5 70
    Japan
    average 74.9 79.1 90.7 73 59.6 81.8 75.8 71.1 65.5 74.8
    after Mean 74.2 67.1 86.1 56.5 64.2 82.5 76.7 63.1 68.7 54.6
    Desired value 69.8 65.6 83.3 55 61.3 76.2 71.4 63 66.7 57.5
    Japan average 73.6 67.7 89.2 55.1 63.2 81.8 75.4 65.9 70.7 58.9
    5th grade before Mean 64.8 59.6 59.4 51.9 57.1 71.2 66.6 56.1 71 33.8
    Desired value 67.7 63.8 68.3 57.5 64.4 71.4 68.9 62 75 42.5
    Japan averageaverage 70.9 66.9 72.3 60.5 66.5 75.3 71.9 66.1 80.8 44
    after Mean 67.7 74.1 73.7 74.5 62.1 65.4 71.9 48.3 52.1 39.9
    Desired value 68.9 70 73.3 68.3 62.4 70.2 73.3 49 55 40
    Japan average 72.3 73.9 75.1 73.1 66.3 72.8 77 50.7 57.9 39.9

    Statistics and software used

    Results of this study were analyzed with statistical software as SPSS 22 version (22.0 J for Windows; SPSS Inc., Chicago, IL, USA). χ2-test was used for categorized variables x categorized variables. Mann-Whitney U-test and Kruskal-Wallis test were used for categorized variables x ratio scale variables. Mental Health Index was expressed as sum of scales on 4 questions on mental health (irritation, anger, out of controlling emotion, depression, distributed from 4 (worst) to 16 (best) points. Wilcoxon test was used for pair-wised comparisons of the questionnaire data before and after the intervention.

    Results

    Sleep habits and meal timing in each grade of elementary school children

    The rate of answer to the questionnaire was more than 95% and the number of data was 295 before and 286 after the intervention. Comparing sleep habits before the intervention, bed time in week days in the second grade students became slightly but significantly earlier after the intervention (Table 2). In the third grade, bed time in week days became earlier and sleep hours were longer after the intervention (Table 3). In the fifth grade, the circadian phase of time when students became sleepy was shifted earlier by 2.5 hours after the intervention (Table 4). In the other grades, there were no significant differences between before and after the intervention in sleep habits and meal timing.

    Table 2. Comparison of bedtime, wake up time and total sleep hours in weekdays in the students of an elementary school, before and after the intervention half-year
               
    Bedtime in WD Wake up time in WD Sleep hours in WD            
    Grade Mean Wilcoxon test Mean Wilcoxon test Mean Wilcoxon test            
    Before after Z-value Pvalue before after Z-value P-value before after Z-value Pvalue            
    1st 21.15 21.16 0.00 1.000 6.67 6.64 -1.03 0.301 9.53 9.48 -1.42 0.157            
    2nd 21.34 21.34 -0.82 0.413 6.58 6.53 -0.29 0.775 9.24 9.19 -0.29 0.768            
    3rd 21.78 21.50 -1.96 0.050* 6.42 6.48 -0.87 0.385 8.65 8.98 -2.24 0.025*            
    4th 21.74 21.67 -0.62 0.536 6.47 6.52 -0.03 0.978 8.70 8.85 -0.95 0.351            
    5th 22.11 22.17 -0.03 0.978 6.43 6.45 -0.15 0.887 8.32 8.27 -0.37 0.712            
    6th 22.08 22.25 -1.81 0.071 6.37 6.50 -1.41 0.159 8.30 8.25 -0.72 0.472            

    Table 3. Comparison of bedtime, wake up time and total sleep hours in weekends in the students of an el-ementary school, before and after the intervention half-year
    Bedtime in WE Wake up time in WE Sleep hours in WE
    Grade Mean Wilcoxon test Mean Wilcoxon test Mean Wilcoxon test
    Before after Z-value Pvalue before after Z-value Pvalue before after Z-value Pvalue Z-value Pvalue
    1st 21.59 21.63 -0.37 0.713 7.31 7.37 -0.44 0.660 9.73 9.74 -0.19 0.849 -0.19 0.849
    2nd 21.34 21.34 -2.92 0.003** 7.14 7.08 -0.64 0.524 9.41 9.50 -1.26 0.209 -1.26 0.209
    3rd 22.29 22.25 -0.18 0.861 7.62 7.31 -1.64 0.101 9.30 9.07 -1.04 0.299 -1.04 0.299
    4th 22.53 22.40 -0.27 0.790 7.50 7.50 -0.14 0.889 9.00 9.10 -0.54 0.558 -0.54 0.558
    5th 22.73 22.68 -0.87 0.381 7.75 8.03 -1.94 0.053 8.74 9.37 -2.19 0.029* -2.19 0.029*
    6th 6.88 6.90 -0.45 0.655 19.67 19.95 -1.09 0.275 21.90 21.29 -0.15 0.877 -0.15 0.877

    Table 4. Comparison of breakfast time, dinner time and sleepy time at night in the students of an elementary school, before and after the intervention half-year
    Bedtime in WE Wake up time in WE Sleep hours in WE
    Grade Mean Wilcoxon test Mean Wilcoxon test Mean Wilcoxon test
    Before after Z-value Pvalue before after Z-value Pvalue before after Z-value Pvalue Z-value Pvalue
    1st 7.00 7.09 -0.60 0.549 18.76 18.74 -0.02 0.983 20.96 20.96 -0.32 0.748 -0.19 0.849
    2nd 7.06 7.05 -0.39 0.700 18.86 18.86 -0.23 0.816 21.08 21.04 -0.91 0.364 -1.26 0.209
    3rd 6.98 7.07 -0.49 0.621 19.39 19.39 -1.64 0.101 -0.70 0.946 -0.51 0.612 -1.04 0.299
    4th 7.05 7.06 -0.65 0.515 19.25 18.83 -0.14 0.889 -0.21 0.830 -0.830 0.404 -0.54 0.558
    5th 6.93 7.07 -0.47 0.636 19.62 18.92 -1.94 0.053 -1.69 0.091 -3.31 0.001** -2.19 0.029*
    6th 6.88 6.90 -0.45 0.655 19.67 19.95 -1.09 0.275 21.90 21.29 -0.15 0.877 -0.15 0.877

    Diurnal type scales and intervention

    The distribution of the diurnal type scale scores before the intervention was similar to that after it (Figure 1). In the histogram on distribution of DTS before intervention, 25 % of evening-typed students significantly shifted to significantly more evening-typed persons (Kruskal wallis test, Morning types and medium types: p>0.05; Evening-types: χ2 value=37.01, df=2, p<0.001) (Figure 2). There was significantly negative correlation between DTS scores before intervention and the amount of increased change in DTS during the intervention period (Pearson’s correlation test: r=-0.390, p<0.01) (Figure 3).

    Sleep quality and sleep duration improved during intervention

    In the first and fifth grades of the elementary school, students improved sleep quality after the intervention (Wilcoxon test: the first grade, z=2.218, p=0.027; the fifth grade, z=2.563, p=0.010) (Figure 4). There was negative correlation between sleep hours in weekday before intervention and increased of sleep hours during the intervention (r=-0.545, p<0.001).

    Sleep hours and academic achievement of Japanese language and mathematics

    Before the intervention, significantly and clear higher mark in academic achievement of Japanese language appeared in the students who had more than 9 hours sleep (Mann-Whitney U-test: z= , p <0.001) (Figure 5). After the intervention, the academic achievement mark in mathematics significantly changed higher than that before it (Pearson’s correlation test: r=0.369, p<0.01) (Figure 6).

    Improvement of academic achievement can be related to change of sleep hours. Students who had increased sleep hours after the intervention showed higher academic achievement marks in mathematics (Mann-Whitney U-test: z=-2.355, p=0.018) (Figure 7)

    Change in breakfast habit during the intervention

    The increase of regularity in breakfast time of day was related to the achievement of Japanese language (Mann-Whitney U-test: z=-2.029, p=0.042) (Figure 8). In the fourth grade, students improved the contents of breakfast with nutritionally well dishes including carbohydrates, protein and vitamins & minerals (Wilcoxon test: the fourth grade, z=2.628, p=0.009).

    Figure1. Distribution of circadian typology and comparison of those before and after the intervention a half year in elementary students aged 7 to 11 years old.
    Figure1.

    Figure 2. Change in the diurnal type scores during the intervention a half year in three chronotypes of morning-ness, medium and eveningness in May 2015 in elementary students aged 7 to 11 years old.
    Figure 2.

    Figure 3. Negative correlation between the diurnal type scale scores before the intervention and the changed value in the scores during the intervention a half year in the elementary students aged 7 to 11 years old. Evening-typed students shifted to more morning typed, whereas morning-typed ones to more evening typed.
    Figure 3.

    Figure 4. Improvement of sleep quality after the intervention in the students of the first grade and the fifth grade in an elementary school, Kochi city, Japan.
    Figure 4.

    Figure 5. Relationship between sleep hours in week days and achievement mark in Japanese language of Japanese elementary students aged 7-11 (second, third and 5th grades students).
    Figure 5.

    Figure 6. Positive correlation between change in academic achievement mark in mathematics and change in sleep hours during the half year intervention in Japanese elementary students aged 7 to 11 years old.
    Figure 6.

    Figure 7. Increased hours of sleep might link to the improvement of academic achievement mark in mathematics of Japanese elementary students aged 7 to 11 years old.
    Figure 7.

    Figure 8. The regularity of breakfast time might link to the improvement of academic achievement mark of Japanese language in elementary students aged 7 to 11 years old.
    Figure 8.

    For all students in the elementary school, there were no significant changes in sleep quality, bedtime in weekdays, wake up time and sleep hours between the intervention period (Tables 1, 2 and 3). There was negative correlation between sleep hours in weekday before intervention and increased amount in sleep hours after that (Pearson’s correlation test: r=-0.545, p<0.001).

    Discussions

    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, one long REM sleep in the morning time zone needs previous long sleep hours. 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 health1, 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 of, first, the having sources of tryptophan and vitamin B6 at breakfast, second, breakfast followed by the exposure to sunlight and, third, the exposure to low temperature lights as night lighting can stimulate the synthesis of serotonin and succeeding melatonin synthesis at night and that these hormones work as natural anti-depression drugs (serotonin) and/or natural sleeping pills (melatonin) and make students more-morning typed and improve their mental health. Higher serotonin level in daytime can make children’s concentration on academic work at school, leading to higher academic marks. Several studies support the hypothesis 14, 15, 16, 17, 18.

    Conclusions

    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.

    Instructions

    - Please, answer the questions on your life habits during the last month.

    - Please, answer the questions in order: do not be back and forth among questions.

    - Please, answer the questions as they are. Answers to the questionnaire will be used only for academic use. You have not to write down your own individual name on the questionnaire.

    - Because this is not an examination, please, feel it easy!

    GENERAL INFORMATIONS

    Gender: □male □female

    Birth date:         , Age:        

    Grade and School:  

    SLEEP HABITS DURING THE WEEK

    1) In weekdays (school days), what time do you go to bed? On average: :

    (eg. 23:30)

    2) In weekdays (school days), how many minutes do you need to fall asleep?

    1. 0-5 min 2. 6-15 min 3. 16-30min 4. 31-45 min

    4. 46-60min 1. more than 1 hour

    3) In weekdays (school days), what time are you awoken? On average:

    (eg. 06:30)

    4) In weekdays (school days), how long do you stay in bed after awoken ?

    1. 0-5 min, 2. 6-15 min, 3. 16-30 min, 4. 31-45 min, 5. 46-60 min, 6.□morethan 1 hour

    SLEEP HABITS DURING THE WEEK-END

    5) In the weekend, what time do you go to bed? On average:

    (eg. 23:30)

    6) In the weekend, how many minutes do you need to fall asleep?

    1.0-5 min 2.6-15 min 3.16-30min 4.31-45 min

    5.46-60min 6.more than 1 hour

    7) In the weekend, what time are you awoken? On average: :

    (eg. 06:30)

    8) At the weekend, how long do you stay in bed after awoken?

    1.0-5 min 2.6-15 min 3.16-30 min 3.31-45 min

    4.46-60min 5.more than 1 hour

    9) At what time in the evening do you feel tired and as a result are you in need of sleep?

    (eg. 22:00) At :

    THE DIURNAL TYPE SCALE

    10) When would you prefer to rise (provided you have a full day’s study-8h) if you were totally free to arrange your time ?

    (4) before 06:30, (3) 06:30-07:29, (2) 07:30-08:29, (1) 08:30 or later

    11) When would you prefer to go to bed (provided you have a full day’s study-8h) if you were totally free to arrange your time?

    (4) before 21:00, (3) 21:00-21:59, (2) 22:00-22:59, (1) 23:00 or later

    12) If you always had to go to bed at 21:00, what do you think it would be like to fall asleep then ?

    (4) easy – would fall asleep practically at once,

    (3) rather easy – would lie awake for a short while,

    (2) rather difficult – would lie awake for some time,

    (1) very difficult – would lie awake for a long time

    13) If always you had to rise at 06:00, what do you think it would be like to get up then ?

    (4) easy – no problem at all

    (3) a little unpleasant but not great problem

    (2) rather difficult and unpleasant

    (1) very difficult and unpleasant

    14) When do you usually begin to feel the first signs of tiredness and need for sleep ?

    (4) before 21:00, (3) 21:00-21:59, (2) 22:00-22:59, (1) 23:00 or later

    15) How long a time does it usually take before you “recover your faculties” in the morning after rising from a night’s sleep?

    (4) 1-10 min., (3) 11-20 min, (2) 21-40 min, (1) more than 40 min

    16) Please, indicate to what extent you are a morning or evening active individual.

    (4) pronounced morning active (morning alert and evening tired)

    (3) to some extent morning active

    (2) to some extent evening active

    (1) pronounced evening active ( morning tired and evening alert)

    Meal haabit questions

    17) What time do you usually take breakfast?

    18) What time do you usually take dinner?

    Acknowledgements

    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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