IMPORTANCE Given the estimates of increasing prevalence of myopia, especially in Asia, it is important to determine the current prevalence of myopia among populations of schoolchildren in Japan.OBJECTIVE To investigate the current prevalence rate of myopia and the association between environmental factors and myopia in Japanese schoolchildren. DESIGN, SETTING, AND PARTICIPANTSThis cross-sectional study assessed 1478 participants, including 726 elementary school students and 752 junior high school students, at 2 schools in Tokyo, Japan, who underwent eye examinations from April 1 to May 31, 2017, that included measurement of the refractive errors by autorefractometry with noncycloplegic refraction and ocular biometric factors. After excluding those who had been treated with atropine or orthokeratology (n = 11), had a history of eye disease (n = 2), had no parental consent (n = 41), and were absent (n = 8), 1416 schoolchildren were analyzed. MAIN OUTCOMES AND MEASURESThe primary outcome was the prevalence of myopia and high myopia. Secondary outcomes were environmental factors that were associated with myopia.RESULTS A total of 1416 schoolchildren (mean [SD] age, 10.8 [2.7] years; 792 [55.9%] male) were studied. The prevalence rates of myopia (spherical equivalent Յ−0.5 diopters [D]) were 76.5% (95% CI, 73.4%-79.7%) among the elementary school students and 94.9% (95% CI, 93.3%-96.5%) among the junior high school students. The prevalence rates of high myopia (spherical equivalent Յ−6.0 D) were 4.0% (95% CI, 2.5%-5.4%) among the elementary school students and 11.3% (95% CI, 8.8%-13.7%) among the junior high school students. The prevalence rates of high myopia classified based on axial length of 26.0 mm or longer were 1.2% (95% CI, 0.4%-2.0%) among elementary school students and 15.2% (95% CI, 12.5%-17.8%) among junior high school students. Multiple regression analysis showed that higher-order aberrations and dry eye disease were associated with refractive error in elementary school students (spherical aberration: β = 6.152; 95% CI, 3.

Overweight is concentrated in a subgroup of children and does not occur across the entire population of British, Dutch, Japanese, and US children, indicating a subgroup of genetically and/or environmentally more susceptible children in each country.

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

The aim of this study was to set forth an age-dependent percentile for waist circumference of Japanese children and to compare the reference with data from other countries. We utilized the 1992-1994 cross-sectional national survey data on waist circumference as measured at two benchmark sites in 10,614 Japanese children (5,851 boys, 4,763 girls) aged 6.0-18.0 years for constructing the reference by the LMS method. Japanese children had smaller waist circumference percentile values as compared to those of Dutch and US children, but had comparable or larger percentile values as compared to those of UK children. We suspect that the observed ethnic differences may be in part due to the differences in benchmark in waist circumference measurements in each country. We present for the first time an age-dependent percentile for waist circumference for Japanese children. It is mandatory to standardize a benchmark site for waist circumference for more meaningful international comparison.

The BMI-SD reference values and charts presented have appropriately reflected the age-dependent skewed distribution of BMI values, and could be a useful tool in growth and nutritional evaluation of Japanese children.