17-year trends of body mass index, overweight, and obesity among adolescents from 2005 to 2021, including the COVID-19 pandemic: a Korean national representative study.

OBJECTIVE: There is a lack of pediatric studies that have analyzed trends in mean body mass index (BMI) and the prevalence of obesity and overweight over a period that includes the mid-stage of the COVID-19 pandemic. Thus, we aimed to investigate trends in BMI, overweight, and obesity among Korean adolescents from 2005 to 2021, including the COVID-19 pandemic. SUBJECTS AND METHODS: We used data from the Korea Youth Risk Behavior Web-based Survey (KYRBS), which is nationally representative of South Korea. The study included middle- and high-school students between the ages of 12 and 18. We examined trends in mean BMI and prevalence of obesity and/or overweight during the COVID-19 pandemic and compared these to those of pre-pandemic trends in each subgroup by gender, grade, and residential region. RESULTS: Data from 1,111,300 adolescents (mean age: 15.04 years) were analyzed. The estimated weighted mean BMI was 20.48 kg/m2 (95% CI, 20.46-20.51) between 2005 and 2007, and this was 21.61 kg/m2 (95% CI, 21.54-21.68) in 2021. The prevalence of overweight and obesity was 13.1% (95% CI, 12.9-13.3%) between 2005 and 2007 and 23.4% (95% CI, 22.8-24.0%) in 2021. The mean BMI and prevalence of obesity and overweight have gradually increased over the past 17 years; however, the extent of change in mean BMI and in the prevalence of obesity and overweight during the pandemic was distinctly less than before. The 17-year trends in the mean BMI, obesity, and overweight exhibited a considerable rise from 2005 to 2021; however, the slope during the COVID-19 pandemic (2020-2021) was significantly less prominent than in the pre-pandemic (2005-2019). CONCLUSIONS: These findings enable us to comprehend long-term trends in the mean BMI of Korean adolescents and further emphasize the need for practical prevention measures against youth obesity and overweight.

Mandibular second molar impaction. Part I: Genetic traits and characteristics.

INTRODUCTION: Detection of mandibular second molar (MM2) impaction is imperative for orthodontic diagnosis and treatment. In this study, we examined a possible genetic trait in MM2 impaction in 2 populations and defined distinctive characteristics. METHODS: Initial panoramic radiographs of patients of Israeli (n = 3500) and Chinese-American (n = 3000) origin, aged 11 to 15 years, were examined. Twelve distinctive characteristics were compared between the unilateral impacted and the nonimpacted sides. RESULTS: A total of 120 subjects with MM2 impaction were found (1.8%). The Chinese-American population had a higher prevalence (n = 71, 2.3%) of MM2 impaction compared with the Israeli population (n = 49, 1.4%; P = 0.004). For the subjects with MM2 impaction, the Israelis had significantly (P = 0.039) fewer bilateral impactions (27%) than did the Chinese-Americans (45%). Mesially inclined impacted MM2s were more common (88% and 89%) in the Israeli and Chinese-American populations, respectively. The unilateral impacted side demonstrated reductions in the distance between the mandibular first molar and the ramus (P <0.001), the length of the mesial root of the MM2 (P <0.001), and the height between the MM2 and the mandibular third molar, and increases in the angulations of the MM2 (P <0.001) and the mandibular third molar (P <0.003). CONCLUSIONS: An autosomal genetic trait is present in MM2 impaction with greater penetrance in the Chinese-American population. Within developmental impediments, the deficient mesial root length of the MM2 is the primary impaction factor.