Relationship between working hours and sleep quality with consideration to effect modification by work style: a community-based cross-sectional study.

BACKGROUND: Although longer working hours are associated with lower sleep quality, it is still necessary to work a certain number of hours to make a living. In this study, we investigated the relationship between working hours and sleep quality in a community setting. We then explored how to manage work style while maintaining the sleep quality of workers without markedly reducing working hours. METHODS: 4388 day-time workers in various occupations living in Ota ward in Tokyo were included in the analysis. The relationship between working hours and sleep quality measured by the Athens Insomnia Scale was examined by ANOVA and linear regression models. Effect modification by work style (work end time, shift in working start and end time, current work from home status, change in work place) on the relationship between working hours and sleep quality was investigated by multivariate linear regression models. RESULTS: Longer working hours were significantly associated with lower sleep quality. The magnitude of the relationship between long working hours and low sleep quality was significantly larger when work end time was later (p for trend of interaction < 0.01) and when working start and end time were shifted later (vs no change, p for interaction = 0.03). The relationship was marginally greater when the proportion of work from home was increased (vs no change, p for interaction = 0.07). CONCLUSIONS: A relationship between longer working hours and lower sleep quality was observed among workers. Leaving work earlier or optimizing the work environment at home may diminish the adverse effect of long working hours on sleep quality.

The Nutritional Characteristics of Usual Lunches Consumed Among Japanese Workers: Comparison Between Different Lunch-Type Groups.

OBJECTIVE: This study investigated whether the nutritional characteristics of lunches consumed by Japanese workers differ by where the meal is usually prepared or eaten. METHODS: This cross-sectional study included 620 employees (aged 20 to 75 years) from eight business offices in Tokyo, Japan. Dietary data were collected using the validated Meal-based Diet History Questionnaire. The Healthy Eating Index 2015 and dietary intakes from lunch were compared between workers classified by usual lunch type: homemade (n = 190), staff canteen (n = 77), restaurant (n = 109), and takeaway (n = 244). RESULTS: Healthy Eating Index 2015 for lunch was highest in the staff canteen group, followed by the homemade group. The staff canteen group had higher intakes of total vegetables, potatoes, fish, and several vitamins from lunch than the restaurant or takeaway groups. CONCLUSIONS: Homemade and canteen lunches are relatively healthy options for lunch for Japanese workers.

Misreporting of height and weight by primary school children in Japan: a cross-sectional study on individual and environmental determinants.

BACKGROUND: Appropriate body constitution during childhood is important for future health. However, it has been suggested that thinness is increasing among adolescent girls and boys in Japan. Since misreporting of height/weight may be a possible reflection of the child's ideal body image, we investigated the magnitude and direction of height/weight misreporting and its determinants among Japanese young adolescents. METHODS: A total of 1019 children in public primary schools were included in the analysis. Both measured and self-reported values of height/weight were obtained. Misreporting of height/weight was calculated by subtracting the measured value from the self-reported value. The association between misreporting and several variables such as the BMI z-score of individuals and body constitution of surrounding children was explored by multivariate linear mixed models. RESULTS: As BMI z-score increased, 'overreporting' of height by boys and 'underreporting' of height by girls became larger (p = 0.06 in boys, p = 0.02 in girls). Both boys and girls with a larger body size tended to underreport their weight (p < 0.01 in boys, p < 0.01 in girls). Boys who belonged to a school with a larger average BMI z-score were more likely to overreport their weight. This tendency was not observed for girls. CONCLUSIONS: Self-reported height/weight was generally accurate in Japanese primary school children. However, even primary school children misreported their height/weight intentionally like adults, possibly due to social pressure to lose weight or that not to stand out. Thus, health education about appropriate body constitution should be provided from the beginning of adolescence, particularly for girls.

Guardianship dietary and other behavioural factors associated with skipping breakfast in Japanese primary school children: A child-guardian dyad study.

BACKGROUND AND OBJECTIVES: Regular breakfast consumption is widely considered an important component of healthy dietary habits. In this study, we assessed differences in nutrient/food intake between breakfast consumers and skippers. We also investigated behavioural factors related with breakfast skipping utilizing data collected from both children and their guardians. METHODS AND STUDY DESIGN: This cross-sectional study was conducted in 14 public primary schools in Japan. Two questionnaires were distributed: a behavioural questionnaire and a brieftype, self-administered diet history questionnaire. In total, 1816 child (10-12 y/o)-guardian dyads were included in the analysis. Intakes of nutrients and foods were compared between breakfast consumers and skippers by the ttest. The relationship between breakfast skipping and behavioural factors was investigated by logistic regression analysis by child sex. RESULTS: The proportion of breakfast skippers in the children was 9.8%. Daily intakes of nutrients/foods were better in the breakfast consumers. Later bedtime, lower nutrition knowledge level, and frequent incomplete consumption of home meals was significantly or marginally associated with breakfast skipping. Guardians' breakfast skipping was also associated with children's breakfast skipping. Some relationships between behavioural factors and breakfast skipping differed between boys and girls. CONCLUSIONS: Breakfast consumers had a more nutritious meal quality. To increase breakfast consumption, morning time schedules may need to be rearranged to avoid time pressure. Nutritional knowledge and dietary behaviour appear relevant. Guardians played a major role in coping with breakfast avoidance, in part as role models.

A school-based nutrition education program involving children and their guardians in Japan: facilitation of guardian-child communication and reduction of nutrition knowledge disparity.

BACKGROUND: Since the risk of noncommunicable diseases is closely associated with dietary intake, it is important to establish healthy dietary habits in childhood. Although several dietary education programs for children have been attempted, their implementation at school was often difficult due to overcrowded study curricula. We developed a new program which included homework for children and guardians, and evaluated its effect. Determinants of the effect were also investigated. METHODS: The school-based nutrition education program including a 45-min lecture, a series of homework assignments involving children and guardians, and two handouts was implemented in 14 public primary schools in Japan. Seven schools each underwent the intervention in an alternating manner. Nutrition knowledge (percentage (%) of correct answers in the nutrition knowledge questionnaire) and attitude/behavior toward diet was evaluated three times (May (baseline), October, February) as outcomes. These factors and their changes following the intervention were assessed by linear mixed models to adjust for individual factors, with consideration to clustering of the participants and repeated measurements. RESULTS: In total, 2227 children aged 10-12 years and their guardians participated. All schools completed the program. Children's nutrition knowledge level was significantly increased (8.7%, 95% confidence interval [7.7-9.7]) following the intervention. Communication between children and their guardians, which was positively related with nutrition knowledge, was facilitated by the intervention. The increase in nutrition knowledge was greater among children with a lower knowledge level at baseline. CONCLUSIONS: This school-based nutrition education program was effective and feasible. Appropriate teaching materials for homework can reduce the burden on schools and facilitate communication between children and guardians. Public schools can be crucial venues for decreasing disparities in nutrition knowledge. TRIAL REGISTRATION: This study was registered as an intervention study in the UMIN Clinical Trials Registry (trial ID: UMIN000029252 ) on Sep 22, 2017.

Relationship between maternal employment status and children's food intake in Japan.

BACKGROUND: Although long maternal working hours are reported to have a negative effect on children's dietary habits, few studies have investigated this issue in Japan. Healthy dietary habits in childhood are important because they may reduce the risk of future disease. Here, we examined the relationship between maternal employment status and children's dietary intake in 1693 pairs of Japanese primary school 5th and 6th graders and their mothers. METHODS: The survey was conducted using two questionnaires, a brief-type self-administered diet history questionnaire and a lifestyle questionnaire. The analysis also considered mothers' and children's nutrition knowledge, attitudes toward diet, and some aspects of family environment. RESULTS: Longer maternal working hours were associated with children's higher intake of white rice (g/1000kcal) (ß 11.4, 95%CI [1.0, 21.9]; working ≥8h vs. not working), lower intake of confectioneries (g/1000kcal) (ß -4.0 [-7.6, -0.4]), and higher body mass index (BMI) (kg/m2) (ß 0.62 [0.2, 1.0]). Although maternal employment status was not significantly associated with lower intake of healthy food (e.g., vegetables) or higher intake of unhealthy food (e.g., sweetened beverages) in the children, in contrast with previous studies, it may have affected children's energy intake through their higher intake of white rice. Further, children's nutrition knowledge and attitudes toward diet, mothers' food intake, and some family environment factors were significantly associated with intakes of vegetables and sweetened beverages in the children. CONCLUSIONS: Longer maternal working hours were significantly associated with higher intake of white rice and lower intake of confectioneries, as well as higher BMI among children. Even when a mother works, however, it may be possible to improve her child's dietary intake by other means such as nutrition education for children or enhancement of food environment.

Vitamin D Status in Japanese Adults: Relationship of Serum 25-Hydroxyvitamin D with Simultaneously Measured Dietary Vitamin D Intake and Ultraviolet Ray Exposure.

Vitamin D insufficiency/deficiency is prevalent worldwide. We investigated the effect of vitamin D intake and ultraviolet ray (UV) exposure on serum vitamin D concentration in Japan. A total of 107 healthy adult participants were recruited from Hokkaido (43°N) and Kumamoto (33°N) prefectures. All participants undertook surveys in both summer and winter. Serum 25-hydroxyvitamin D (25(OH)D3) was examined, and vitamin D intake was assessed with a diet history questionnaire. UV exposure was measured with a wearable UV dosimeter. Regression analysis was performed to investigate the relationship between these factors, with covariates such as sun avoidance behavior. The prevalence of vitamin D insufficiency (serum 25(OH)D3; 12 ng/ml (30 nmol/L) ≤ and <20 ng/ml (50 nmol/L))/deficiency (<12 ng/ml) was 47.7% in summer and 82.2% in winter. UV exposure time was short in Kumamoto (the urban area), at 11.6 minutes in summer and 14.9 minutes in winter. In Hokkaido (the rural area), UV exposure time was 58.3 minutes in summer and 22.5 minutes in winter. Vitamin D intake was significantly associated with serum 25(OH)D3, and a 1 µg/1000kcal increase in intake was necessary to increase 25(OH)D3 by 0.88 ng/ml in summer and by 1.7 ng/ml in winter. UV exposure time was significantly associated with serum 25(OH)D3 in summer, and a 10 min increase in UV exposure time was necessary to increase 25(OH)D3 by 0.47 ng/ml. Although consideration of personal occupation and lifestyle is necessary, most Japanese may need to increase both vitamin D intake and UV exposure.