Underweight in young Japanese women over time: a longitudinal retrospective study of the change in body mass index from ages 6 to 20 years.

BACKGROUND: The high prevalence of underweight in young women has become a serious health problem in Japan. When and how young women reach a low body mass index (BMI) has not been clarified. AIM: To clarify the characteristics of BMI standard deviation scores (BMI SDS) trajectory of young Japanese women with underweight. SUBJECTS AND METHODS: A total of 601 Japanese female university students aged 20 years were classified into underweight and healthy weight groups. Their school health check-up data were available from the ages of 6 to 20 years. We evaluated the estimated mean values of BMI SDS at each age and differences in BMI SDS (ΔBMI SDS) from 6 years to each age using a mixed-effects model and compared between the two groups at each age. RESULTS: In the underweight group, the BMI SDS at every age (-1.67 to -0.91) and the ΔBMI SDS after 16 years of age (-0.76 to -0.38) were significantly lower than those in the healthy weight group (-0.41 to -0.13, -0.07 to 0.04), respectively. CONCLUSION: Young Japanese women with underweight have at least two characteristics of BMI SDS trajectory: being constitutionally underweight and shifting their weight status from baseline towards underweight in their late teens.

Pediatric blood pressure category predicts longitudinal blood pressure change in adolescence and early adulthood.

BACKGROUND: Patterns of blood pressure (BP) change from early adolescence to young adulthood have not been well-described. The objective of this study was to examine the predictive value of pediatric BP classification on BP change and identify subpopulations with large BP increases during adolescence and early adulthood. METHODS: Baseline data were obtained from medical checkups of Japanese adolescents aged 12-13 years in 2009 or 2010 and subsequent BP values were followed for a 9-year period. Mixed-effects models were used to estimate the effects of baseline factors on subsequent BP changes. RESULTS: Hypertensive and elevated BP group consistently had higher BP values than normal BP group throughout the observation period. Multivariate mixed-effects model analyses revealed group-by-time interactions between systolic BP change and BP category in males and uric acid category in females, and between diastolic BP change and white blood cell count in males and obesity and high-density lipoprotein cholesterol in females; however, these factors had limited effects on the rate of BP increase, indicating that they are not suitable as clinical predictors of BP increase. CONCLUSIONS: Pediatric BP category predicted BP values, but there was no factor that identified subpopulations with large BP increases in adolescence and early adulthood. IMPACT: Blood pressure category in the American Academy of Pediatrics clinical practice guideline at age 12-13 years predicted subsequent blood pressure values during adolescence and early adulthood. No baseline factor that identified a subpopulation with large increase in blood pressure during adolescence and early adulthood in clinical practice was found. Our study contributes to the existing literature by demonstrating the usefulness of the American Academy of Pediatrics clinical practice guideline for blood pressure classification in a Japanese population.

Impact of school closure due to the coronavirus disease 2019 pandemic on body mass index in Japanese children: Retrospective longitudinal study.

AIM: During the coronavirus disease 2019 pandemic, the governments of many countries responded to high levels of infection with lockdowns. As a result, some children were reported to experience weight gain. The aim of the present study was to examine the impact of school closures on body mass index (BMI) in Japanese children. METHODS: This was a retrospective study of students enrolled in the participating schools (6- to 11-year-old elementary school students and 12- to 14-year-old junior high school students) between 2015 and 2020. Using school health check-up data, annual changes in the BMI standard deviation score (ΔBMI-SDS) were calculated. We compared ΔBMI-SDS in 2019-2020 with the corresponding control years. RESULTS: 19 565 children with complete data were included in the analysis. Median ΔBMI-SDS in 2019-2020 were 0.24-0.35 in elementary school boys, 0.10-0.13 in junior high school boys, -0.02 to 0.15 in elementary school girls and -0.14 to -0.10 in junior high school girls. In comparison with every control year, ΔBMI-SDS in 2019-2020 were significantly higher in elementary school boys (control years: -0.07 to 0.14) and junior high school boys (control years: -0.04 to 0.06), and significantly lower in junior high school girls (control years: -0.06 to 0.09). CONCLUSION: BMI-SDS increased significantly in elementary and junior high school boys, but decreased significantly in junior high school girls. The pandemic appears to have had an impact on Japanese children that was different from other countries.

Reference values of inside leg length and inside leg length to stature ratio for Japanese children, 0-12 years of age.

BACKGROUND: Large datasets of detailed anthropometric measurements are scarce in children. The Japanese Standard Association 1978-1981 survey provides a rare opportunity to use high quality data from Japanese children. AIM: To construct inside leg length (ILL) and inside leg length to stature ratio (ILL/S) reference centile curves for Japanese children. SUBJECTS AND METHODS: The study sample consisted of 14,825 boys and 14,577 girls age 0-18 years for stature and weight measurements, and 9064 boys and 8796 girls age 0-12 years for ILL measurements, who participated in the 1978-1981 national survey on body sizes. LMS method was used to construct the reference centile curves. The reference centile curves for stature, weight, ILL, and ILL/S were compared to those of British children. RESULTS: The L, M, and S reference values for Japanese children are presented for stature, weight, ILL, and ILL/S. Compared with British children of 0-12 years of age, Japanese children of 0-12 years of age had shorter median stature, shorter median ILL, and shorter median ILL/S. CONCLUSION: We present the first reference values for ILL and ILL/S in Japanese children. Japanese children had relatively shorter legs compared to British children from infancy.

Policy statement of enteral nutrition for preterm and very low birthweight infants.

For preterm and very low birthweight infants, the mother's own milk is the best nutrition. Based on the latest information for mothers who give birth to preterm and very low birthweight infants, medical staff should encourage and assist mothers to pump or express and provide their own milk whenever possible. If the supply of maternal milk is insufficient even though they receive adequate support, or the mother's own milk cannot be given to her infant for any reason, donor human milk should be used. Donors who donate their breast milk need to meet the Guideline of the Japan Human Milk Bank Association. Donor human milk should be provided according to the medical needs of preterm and very low birthweight infants, regardless of their family's financial status. In the future, it will be necessary to create a system to supply an exclusive human milk-based diet (EHMD), consisting of human milk with the addition of a human milk-derived human milk fortifier, to preterm and very low birthweight infants.

Low birth weight is associated with decline in renal function in Japanese male and female adolescents.

BACKGROUND: Low birth weight (LBW) is a risk factor for chronic kidney disease (CKD) in later life and is becoming increasingly common in developed countries, including Japan. Furthermore, a serial decrease in birth weight has been associated with an increasing prevalence of CKD stage 2 in male Japanese adolescents. Sex-specific differences affect CKD susceptibility, and the association between birth weight and CKD in women, has not been elucidated. In this study, we investigated the sex-specific effect of LBW on renal function. METHODS: Annual cross-sectional data of 2417 Japanese adolescents (males 1736; females 681), aged 15-16 years, were evaluated over 8 years (2007-2014). RESULTS: Over the study period, mean birth weights decreased significantly in males (p < 0.01) and females (p < 0.05). Furthermore, both sexes showed significant decrease in estimated glomerular filtration rates corresponding to the birth weight reduction. The prevalence of CKD stage 2 also increased in males (from 26.0 to 32.4%, p < 0.01) and females (from 6.3 to 18.5%, p < 0.05). The incidence of CKD stage 2 was significantly related to history of LBW (males: odds ratio 1.73; 95% confidence interval 1.06-2.80; p < 0.05; females: odds ratio 3.29; 95% confidence interval 1.25-8.02; p < 0.05). CONCLUSIONS: Our data revealed that renal function and birth weight have decreased over time, in healthy Japanese adolescents. In view of the recent declining trend demonstrated by birth weight in Japan, we speculate that the prevalence of CKD might increase in the future.

National anthropometric reference values and growth curves for Japanese children: history and critical review.

Context: Child health statistics are a critical component of child health assessment. However, the importance of nationally representative data on growth is not well recognised for Japanese children. Objective: The aim of this paper is to review the national growth surveys for Japanese children and to discuss the clinical use of the national growth reference values and growth curves. Methods: There are five governmental organisations surveying health and growth in Japanese children. Based on these studies, several aspects of the current governmental policy on child growth assessment have been examined. This review focussed on national anthropometric studies reported by Japanese investigators in English for international readers to understand Japanese issues. Results: A variety of growth reference curves have been developed since the early 1980s in Japan. However, these references have several limitations: incomplete data for both infants and young adults, limited description of socio-economic factors and continued governmental use of weight-for-height rather than BMI. Conclusion: Japanese child health statistics use measures that are applicable only to Japanese children.

Temporal trends in renal function and birthweight in Japanese adolescent males (1998-2015).

Background: Low birthweight (LBW) is a worldwide public health problem, demonstrating an increasing incidence in developed countries, including Japan. LBW is also a risk factor for later development of chronic kidney disease (CKD). To date, studies have not evaluated the population impacts of increasing LBW rates on renal function. Methods: Estimated glomerular filtration rate (eGFR) was evaluated in 3737 Japanese adolescent males (15-16 years old) using annual cross-sectional data over an 18-year period (1998-2015). Results: Between the initial (1998-2003) and final (2010-15) periods of the study, the mean birthweight decreased from 3213.4 ± 383.8 to 3116.2 ± 382.3 g and the LBW rate increased from 2.5 to 5.5% (both P ≤ 0.01). Additionally, the mean eGFR decreased from 105.1 ± 15.9 to 97.4 ± 13.8 mL/min/1.73 m2 and the prevalence of mildly reduced renal function (eGFR ≤ 60- <90 mL/min/1.73 m2) increased from 16.4 to 30.0% (both P ≤ 0.01), most evident in the LBW group (from 10.3 to 41.7%, P ≤0.01). The prevalence of proteinuria also increased significantly. Mildly reduced renal function was significantly associated with LBW [odds ratio (LBW 3000-3999 g) 1.51; 95% confidence interval 1.00-2.55; P = 0.047]. Conclusions: In this population of Japanese adolescents, the frequency of mildly reduced renal function increased as the LBW frequency increased. Our findings may have implications for the broader Japanese population as well as for other populations in which the prevalence of LBW is increasing.

Prevalence of central fatness in 1992-1994: 40% of Japanese boys 6-17 years.

Obesity in children is a serious public health problem in Japan. However, the prevalence of central fatness has not been well determined in Japanese youth. We studied the relationship between body mass index (BMI) and waist circumference (WC) using line of equality analysis in 5,787 boys and 4,639 girls aged 6 to 17 years who participated in the 1992-1994 national survey on body sizes. WC was measured at the level of maximum waist narrowing in girls (WC1) and at the level of the top of iliac crest in boys (WC2). Using the 1978-1981 national survey data as baseline reference, excess fatness was defined as measurements exceeding the 90th centile in WC or in BMI. Among boys, 2,466 (42.6%) had WC2 >90th centile and 1,029 (17.8%) BMI >90th centile; whereas among girls, 895 (19.3%) had WC1 >90th centile and 673 (14.5%) BMI >90th centile. WC2-standard deviation scores (SDS) exceeded BMI-SDS in 5,060 (87.4%) boys and WC1-SDS exceeded BMI-SDS in 3,168 (68.3%) girls, respectively. Our results suggested a much higher prevalence of central fatness than generally recognized for Japanese children and adolescents, in particular, in Japanese boys.

Trends in thin body stature among Japanese female adolescents, 2003-2012.

BACKGROUND: The past decades have witnessed a steady increase in thin body stature associated with unhealthy dieting among Japanese female adolescents. The most recent trends in thinness, however, have not been reported. AIM: To describe changes in the distribution of body mass index (BMI) of Japanese female adolescents, from 2003-2012. SUBJECTS AND METHODS: This study examined BMI distribution changes in 2541 relatively affluent Japanese girls, aged 12.5-17.5 years, during 2003-2012. The 2003 and 2004 data were combined and compared to the combined 2011 and 2012 data. Tukey mean-difference plots were used to study the direction and magnitude of shifts in BMI distributions. RESULTS: Prevalence of thinness (BMI <5th percentile of the 1978-1981 references) has progressively increased from 2.0-5.7% in 2003-2004 to 3.5-7.8% in 2011-2012 in Japanese girls. The downward shift in BMI was larger in 12.5-14.5 year olds than in 15.5-17.5 year olds and more prominent in the lower BMI spectrum. CONCLUSION: The trend towards thinness has continued in Japanese girls during the past decade. The distribution of BMI suggests thinner and younger sub-groups of girls are more susceptible to this trend.

Waist circumference centiles by age and sex for Japanese children based on the 1978-1981 cross-sectional national survey data.

AIM: The aim of this study was to establish reference values for waist circumference among Japanese youths using the 1978-1981 nationally representative data. SUBJECT AND METHODS: Growth charts were derived using Cole's LMS method, which adjusts the waist circumference distribution for skewness and allows waist circumference to be expressed as centile or standard deviation score. The sample population consisted of 19 233 children aged 6-18 years. Waist circumference was measured at the level of maximum waist narrowing in girls and at the level of the top of the iliac crest in boys. RESULTS: Comparison was made between the 1978-1981 and 1992-1994 waist circumference charts, showing a large increase in waist circumference over time; the mean difference was 1.1 and 0.5 SD score units in boys and girls, respectively. Defining cut-offs for central fatness as the 90th and 95th centiles of the 1978-1981 reference, the prevalences in 1992-1994 were, respectively, 42.3% and 25.2% in boys and 19.1% and 10.9% in girls. The corresponding prevalences in 1978-1981 were 10% and 5% by definition. CONCLUSION: This study showed increasing trends in waist circumference, particularly in boys during the period of the two surveys and that the 1978-1981 charts serve as better baseline references for waist circumference among Japanese youth.

Trends in thin body stature among Japanese male adolescents, 2003-2012.

BACKGROUND: The desire for thin body stature and unhealthy eating behaviours have spread among Japanese boys. The prevalence of thinness in boys is expected to increase; however, recent trends have not been reported. AIM: To describe changes in the distribution of body mass index (BMI) of Japanese boys, from 2003 to 2012. SUBJECTS AND METHODS: BMI distribution changes were studied in 2599 relatively affluent Japanese children and adolescents, aged 12.5-17.5 years, during 2003-2012. The 2003 and 2004 data were combined and compared to the combined 2011 and 2012 data. Tukey mean-difference plots were used to study the direction and magnitude of shifts in BMI distributions. RESULTS: Prevalence of thinness has progressively increased from 2.8-4.7% in 2003-2004 to 5.1-7.6% in 2011-2012 in Japanese boys. Tukey plots showed that the increases in the prevalence of thinness are related to shifts in the entire distribution of BMI in the sample. CONCLUSION: Thin body stature was documented in increasing proportion of Japanese male adolescents. BMI z-scores decreased across the entire BMI centile spectrums, indicating that the whole school population may be at risk of thinness.

Secular trends and age-specific distribution of blood pressure in Japanese adolescents aged 12-18 years in 2000-2019.

Adolescent blood pressure is a predictor of future risk for hypertension and cardiovascular diseases, and therefore its status needs to be accurately determined. However, limited evidence is available regarding the secular trends and distribution of adolescent blood pressure. In the present study, we assessed the secular trends and age-specific distributions of blood pressure in Japanese adolescents aged 12-18 years by using data drawn from 20 years of annual health checkups conducted between 2000 and 2019. Participants underwent health checkups every year for three years at the same school and the data were divided into four 5-year cycles: 2000-2004, 2005-2009, 2010-2014, and 2015-2019. From a total of 124,460 records (33,496 individuals) retrieved, 3000 records (3000 individuals) from each year-cycle were randomly selected to avoid duplicating data from the same individuals. In the study period, in males systolic blood pressure showed a decreasing trend over time, whereas in females diastolic blood pressure showed an increasing trend. Subgroup analyses by school category (junior/senior high school) and by obesity category showed similar blood pressure trends as in the overall analysis. Age-specific blood pressure values in Japanese adolescents increased with age in males but not in females. Thus, different patterns of change in blood pressure values over the past 20 years were observed between males and females. Age-specific blood pressure distributions are also presented. Together, these findings will be useful for understanding blood pressure trends among adolescents.

Fluorodeoxyglucose-positron emission tomography as a potential alternative tool for functional diagnosis of glycogen storage disease type I.

A 43-year-old woman with genetically confirmed glycogen storage disease type Ib was suspected to have left breast cancer. Fluorodeoxyglucose-positron emission tomography showed high fluorodeoxyglucose accumulation in the whole liver as well as left mammary gland. We consider that high fluorodeoxyglucose accumulation in the liver of patients with glycogen storage disease type I is caused by impaired glucose-6-phosphate metabolism due to the congenital deficiency of glucose-6-phosphatase activities in hepatocytes. This study describes fluorodeoxyglucose-positron emission tomography as a potential alternative tool to diagnose glycogen storage disease type I functionally.

Children in Tokyo Have a Long Sustained Axial Length from Age 3 Years: The Tokyo Myopia Study.

Background: myopia prevalence is high among Japanese schoolchildren, but the underlying causes are unclear. Objective: To examine the distributions of ocular biometry and refraction and their associations with lifestyle variables among Japanese schoolchildren. Methods: This cross-sectional school-based study included 2140 children aged 3−14 years in Tokyo, Japan, and evaluated the distributions under non-cycloplegic conditions and the associated environmental factors. Results: The prevalence of spherical equivalent (SE) ≤−0.75 diopter among preschoolers (aged 3−6 years), elementary school students (aged 6−11 years), and junior high school students (aged 12−14 years) was 49.7%, 72.4%, and 87.7%, respectively. Multiple linear regression analyses showed that the time spent using digital devices was associated positively with lens thickness (ß = 0.010; p < 0.050) but not SE, axial length, or vitreous chamber depth. The time spent reading was associated negatively with lens thickness (ß = −0.012; p < 0.050), SE (ß = −0.152; p < 0.010), axial length (ß = 0.110; p < 0.001), and vitreous chamber depth (ß = 0.110; p < 0.001). Conclusions: The data indicated that almost half of preschoolers may be myopic. The association with the lens thickness differed depending on the type of near work performed.

Influenza vaccination of schoolchildren and influenza outbreaks in a school.

BACKGROUND: The objective of this retrospective descriptive study was to determine whether the universal influenza vaccination for schoolchildren was effective in controlling influenza outbreaks in a school. A universal vaccination program for schoolchildren was started in Japan in the 1960s, but the government abandoned the program in 1994 because of lack of evidence that the program was effective in preventing influenza in schoolchildren. METHODS: Influenza vaccine coverage rates, total numbers of class cancellation days, and absentee rates were reviewed in a single elementary school during the 24-year period during 1984-2007. RESULTS: The mean number of class cancellation days and the mean absentee rate in the compulsory vaccination period (1984-1987; mean vaccine coverage rate, 96.5%) were 1.3 days and 2.5%, respectively, and they increased to 8.3 days and 3.2% during the quasi-compulsory vaccination period (1988-1994; vaccine coverage, 66.4%). In the no-vaccination period (1995-1999; vaccine coverage, 2.4%), they were 20.5 days and 4.3%, respectively, and in the voluntary vaccination period (2000-2007; vaccine coverage, 38.9-78.6%), they were 7.0-9.3 days and 3.8%-3.9%. When minor epidemics were excluded, there was a significant inverse correlation between the vaccine coverage rates and both the number of class cancellation days and absentee rates. CONCLUSIONS: The universal influenza vaccination for schoolchildren was effective in reducing the number of class cancellation days and absenteeism in the school.

Tracking of BMI in Japanese children from 6 to 18 years of age: Reference values for annual BMI incremental change and proposal for size of increment indicative of risk for obesity.

BACKGROUND: A large incremental increase in BMI indicates excess fat deposition in most children, but the reference values for identifying those at risk for developing obesity have not been defined. AIM: To determine the mean and SD of annual incremental change (ΔSDS) in BMI for Japanese school children. SUBJECTS AND METHODS: A cohort of 669 Japanese children in one private school in Tokyo in whom height and weight were measured annually between 6-17 years of age. Each child's BMI was converted to SDS as based on the 1978-1981 Japanese references for the 12 annual measurements to derive the correlation coefficient, r, between two successive measurements. Using the formula, SD of ΔSDS = √2(1-r), the mean and SD of ΔSDS were obtained. RESULTS: Excess BMI gain was defined in terms of ΔSDS in Japanese children. Annual incremental increase greater than 2 SD of ΔSDS, equivalent to 1-2 BMI units/year for younger children and 2-3 BMI units/year for older children, respectively, indicates rapid increase in body fat in Japanese children. CONCLUSION: Based on analysis of incremental change in BMI in this cohort, a cut-off has been identified that can be used to identify children at risk for developing obesity.

BMI z-score is the optimal measure of annual adiposity change in elementary school children.

BACKGROUND: BMI or BMI% adjusted for age has been identified as the optimal measure of short-term adiposity change in kindergarten children aged 29-68 months. The optimal measure of annual adiposity change in older age children, however, has not been determined. AIM: To identify the optimal measure of annual adiposity change for Japanese children aged 6-12 years. SUBJECTS AND METHODS: A cohort of 669 Japanese children in one private school in Tokyo in whom height and weight were measured annually between 6 and 12 years. Each child's annual variability in adiposity was summarized by the standard deviation (SD) of BMI and BMI% adjusted for age, BMI z-score and BMI centile. The SDs were compared in overweight and non-overweight children and correlated with each child's baseline BMI z-score. RESULTS: The within-child BMI, BMI% and BMI centile SDs were significantly different in overweight and non-overweight children, while the BMI z-score SDs were similar in the two groups. Furthermore, the within-child BMI, BMI% and BMI centile SDs were inversely correlated with baseline BMI z-score, whereas BMI z-score SDs were not, with the exception of measurements for grade 1-2 children. CONCLUSION: The BMI z-score is the optimal measure of annual adiposity change for elementary school children.

Population-based waist circumference reference values in Japanese children (0-6 years): comparisons with Dutch, Swedish and Turkish preschool children.

BACKGROUND: During 1978-1981 the Japanese Standards Association conducted a national survey to collect 64 distinct body measurements for Japanese children and adults. During 1978-1981, the prevalence of childhood obesity was relatively low yet the population was well nourished in Japanese children. The aim of this study is to construct waist circumference and waist circumference to stature ratio reference centile curves for Japanese preschool children. METHODS: We utilized 1978-1981 national survey data on body sizes. There are 4937 boys and 4758 girls age 0-6 years for waist circumference measurements. Waist circumference was measured at the level of the umbilicus. Using LMS method, centile curves were constructed for waist circumference and waist circumference to stature ratio. These reference values were compared with those of Dutch, Swedish and Turkish children. RESULTS: Centile reference curves were made for clinical and epidemiological use. Japanese children had smaller waist circumference centile values as compared to waist circumference measured at the midpoint of the lowest rib cage and the iliac crest of Dutch, Swedish and Turkish children. However, Japanese children had comparable waist circumference to stature ratio centile values to those of Dutch and Turkish children. CONCLUSIONS: This study presents the first age-, sex-, and ethnicity-specific reference values for waist circumference and waist circumference to stature ratio in Japanese preschool children.

Changes in epidemiological characteristics and sero-prevalence against the varicella zoster virus in school-age children after the introduction of a national immunization program in Japan.

A national immunization program using two doses of live attenuated varicella vaccine was introduced for children aged one to two years in Japan in October 2014. Varicella cases declined after 2014, and immunological status against varicella among vaccinated children changed in post-vaccination era. A retrospective observational study of anti-varicella antibody seroprevalence, varicella vaccination status, and history of varicella among 528 students in the first grade of elementary school was conducted. The percentage of students who received at least a single dose of varicella vaccination increased from 67% (187 of 279 students) in 2007-2008 to 91% (226 of 249 students) in 2017. Students with a history of varicella decreased from 114 of 279 (41%) in 2007-2008 to 48 of 249 (19%, P < .01) in 2017. Among them, the rate of breakthrough varicella after a single dose of vaccine in students with a history of varicella significantly increased from 38% (43 of 114 students) in 2007-2008 to 58% (28 of 48 students) in 2017 (P < .05). The antibody-positive rate significantly decreased from 50% among subjects without varicella zoster who received a single dose (95%CI: 41-58%) in 2007-2008 to 29% (95%CI: 21-38%) in 2017 (P < .01). The antibody-positive rate among students without varicella history who received two doses of vaccine was only 43% (95%CI: 32-55%) in 2017. The number of varicella infections and antibody-positive rate among students without history of varicella who received varicella vaccination decreased after the introduction of a national immunization program.