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· The prevalence of metabolic syndrome increased in Korean children during the coronavirus disease 2019 pandemic owing to reduced physical activity resulting from social distancing. · Metabolic syndrome impacts pulmonary dysfunction in childhood asthma. · Further studies are needed to understand the mechanism linking asthma and metabolic syndrome and develop interventions. KCI Citation Count: 0

Background Community–acquired pneumonia (CAP) is one of the leading worldwide causes of childhood morbidity and mortality. Its disease burden varies by age and etiology and is time dependent. We aimed to investigate the annual and seasonal patterns in etiologies of pediatric CAP requiring hospitalization. Methods We conducted a retrospective study in 30,994 children (aged 0–18 years) with CAP between 2010 and 2015 at 23 nationwide hospitals in South Korea. Mycoplasma pneumoniae (MP) pneumonia was clinically classified as macrolide-sensitive MP, macrolide-less effective MP (MLEP), and macrolide-refractory MP (MRMP) based on fever duration after initiation of macrolide treatment, regardless of the results of in vitro macrolide sensitivity tests. Results MP and respiratory syncytial virus (RSV) were the two most commonly identified pathogens of CAP. With the two epidemics of MP pneumonia (2011 and 2015), the rates of clinical MLEP and MRMP pneumonia showed increasing trends of 36.4% of the total MP pneumonia. In children < 2 years of age, RSV (34.0%) was the most common cause of CAP, followed by MP (9.4%); however, MP was the most common cause of CAP in children aged 2–18 years of age (45.3%). Systemic corticosteroid was most commonly administered for MP pneumonia. The rate of hospitalization in intensive care units was the highest for RSV pneumonia, and ventilator care was most commonly needed in cases of adenovirus pneumonia. Conclusions The present study provides fundamental data to establish public health policies to decrease the disease burden due to CAP and improve pediatric health.

Mycoplasma pneumoniae is a major causative pathogen of community-acquired pneumonia in children, and the treatment of choice is macrolides. There is an increasing trend in reports of refractory clinical responses despite macrolide treatment due to the emergence of macrolide-resistant M. pneumoniae. Early discrimination of macrolide-refractory M. pneumoniae pneumonia (MrMP) from macrolide-sensitive M. pneumoniae pneumonia (MSMP) is vital; however, testing for macrolide susceptibility at the time of admission is not feasible. This study aimed to identify the characteristics of MrMP in Korean children, in comparison with those of MSMP. In this multicenter study, board-certified pediatric pulmonologists at 22 tertiary hospitals reviewed the medical records from 2010 to 2015 of 5294 children who were hospitalized with M. pneumoniae pneumonia and administered macrolides as the initial treatment. One-way analysis of variance and the Kruskal-Wallis test were used to compare differences between groups. Of 5294 patients (mean age, 5.6 years) included in this analysis, 240 (4.5%), 925 (17.5%), and 4129 (78.0%) had MrMP, macrolide-less effective M. pneumoniae pneumonia, and MSMP, respectively. Compared with the MSMP group, the MrMP group had a longer fever duration, overall (13.0 days) and after macrolide use (8.0 days). A higher proportion of MrMP patients had respiratory distress, pleural effusion, and lobar pneumonia. The mean aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and C-reactive protein levels were the highest in the MrMP group, along with higher incidences of extrapulmonary manifestations and atelectasis (during and post infection). Pre-existing conditions were present in 17.4% (n = 725/4159) of patients, with asthma being the most common (n = 334/4811, 6.9%). This study verified that MrMP patients show more severe initial radiographic findings and clinical courses than MSMP patients. MrMP should be promptly managed by agents other than macrolides.

Introduction Macrolide‐resistant Mycoplasma pneumoniae (MRMP) has become prevalent in children. This study investigated the clinical and laboratory variables of MRMP and macrolide‐sensitive M. pneumoniae (MSMP) and identified factors associated with prolonged hospital admission in children. Methods A prospective multicenter study was conducted in 1063 children <18 years old in July 2018–June 2020. The 454 had a positive M. pneumoniae polymerase chain reaction assay. Results Most subjects had MRMP (78.4%), and all mutated strains had the A2063G transition. We defined MRMP* (n = 285) as MRMP pneumonia requiring admission and MSMP* (n = 72) as MSMP pneumonia requiring admission. Patients with MRMP pneumonia were older, more likely to have segmental/lobar pneumonia, and had more febrile days than those with MSMP pneumonia. C‐reactive protein (CRP), lactate dehydrogenase (LDH), and percentage neutrophils were more strongly associated with MRMP* than MSMP* groups. Percentage neutrophils, CRP, and alanine aminotransferase significantly changed between admission and follow‐up measurements in patients with MRMP* (P < 0.05). The duration of admission positively correlated with the number of febrile days after initiation of antibiotic medication and laboratory variables (white blood cell count, CRP, and aspartate aminotransferase [AST]) (P < 0.05). Random forest analysis indicated that the number of febrile days after initiation of antibiotic medication, AST, and percentage neutrophils at admission was over five. Conclusions This study indicated that children with M. pneumoniae pneumonia with a higher number of febrile days after initiation of antibiotic medication, AST, and percentage neutrophils at admission were more likely to have prolonged admission duration. Macrolide‐resistant Mycoplasma pneumoniae (MRMP) has become prevalent in children. Children with M. pneumoniae pneumonia with a higher number of febrile days after initiation of antibiotic medication, AST, and percentage neutrophils at admission were more likely to have prolonged admission duration.

Investigating the impact of urinary mercury and cadmium on anthropometric parameters in Korean children is crucial amid growing concerns about heavy metal exposure and childhood growth. Using data from the Korean National Environmental Health Survey (2015–2017), we assessed age- and sex-specific associations of urinary mercury and cadmium with height and body mass index (BMI) z-scores in 1458 children aged 3–5 (n = 571) and 6–11 years (n = 887). Overall, 5.0% had stunted height (3–5 years: 6.9%, 6–11 years: 3.8%), whereas older children exhibited higher overweight/obesity prevalence (29.2%) than younger ones did (22.2%). In 3–5-year-old boys, urinary mercury correlated negatively with height z-scores (p < 0.001), whereas in girls, urinary cadmium correlated positively (p = 0.015). Boys aged 6–11 years showed positive associations between mercury/cadmium levels and BMI z-scores (p = 0.012). Logistic regression indicated associations between urinary mercury and stunted height likelihood (p = 0.001) and between urinary cadmium and reduced overweight likelihood (p = 0.039) in 3–5-year-old boys. In boys aged 6–11 years, urinary cadmium levels were positively associated with overweight likelihood (p = 0.003). This study underscores the link between elevated urinary mercury, cadmium levels, and growth disruptions in Korean children, emphasizing the need for public health strategies for reducing childhood heavy metal exposure.

The efficiency improvement of organic light-emitting diodes (OLEDs) is important but challenging. Here, we introduce a unique OLED with a hole modulation layer (HML) in the middle of its emission layer (EML). The external quantum efficiency and power efficiency can be improved by approximately 58% when an HML with optimized thickness is inserted. HML insertion can efficiently retard hole flow, thus improving ( i ) exciton distribution uniformity and ( ii ) local electron–hole charge balance. A systematic study of the individual contributions of two EMLs separated by the HML shows that the former factor dominantly works at low current densities (< 10 mA/cm 2 ), whereas the latter factor functions over the entire current density range of the OLED. Therefore, the efficiency improvement is greatest at low current densities, which aligns with the typical operating range in display applications. The results provide a deeper understanding of the OLED emission mechanism, and the proposed OLED structure can significantly benefit high-performance OLED displays. Graphical Abstract

Although cesarean delivery and prenatal exposure to antibiotics are likely to affect the gut microbiome in infancy, their effect on the development of atopic dermatitis (AD) in infancy is unclear. The influence of individual genotypes on these relationships is also unclear. To evaluate with a prospective birth cohort study whether cesarean section, prenatal exposure to antibiotics, and susceptible genotypes act additively to promote the development of AD in infancy. The Cohort for Childhood of Asthma and Allergic Diseases (COCOA) was selected from the general Korean population. A pediatric allergist assessed 412 infants for the presence of AD at 1 year of age. Their cord blood DNA was subjected to interleukin (IL)-13 (rs20541) and cluster-of-differentiation (CD)14 (rs2569190) genotype analysis. The combination of cesarean delivery and prenatal exposure to antibiotics associated significantly and positively with AD (adjusted odds ratio, 5.70; 95% CI, 1.19-27.3). The association between cesarean delivery and AD was significantly modified by parental history of allergic diseases or risk-associated IL-13 (rs20541) and CD14 (rs2569190) genotypes. There was a trend of interaction between IL-13 (rs20541) and delivery mode with respect to the subsequent risk of AD. (P for interaction = 0.039) Infants who were exposed prenatally to antibiotics and were born by cesarean delivery had a lower total microbiota diversity in stool samples at 6 months of age than the control group. As the number of these risk factors increased, the AD risk rose (trend p<0.05). Cesarean delivery and prenatal antibiotic exposure may affect the gut microbiota, which may in turn influence the risk of AD in infants. These relationships may be shaped by the genetic predisposition.

Efficient charge generation is essential for tandem organic light-emitting diode (OLED) devices. In this study, we introduce a p-type copper iodide (CuI) layer within the charge generation layer (CGL) that exhibits high charge generation efficiency in tandem OLED devices. Briefly, CuI is deposited as a thin layer via thermal evaporation technique. X-ray diffraction (XRD) analysis reveals the formation of γ-CuI, and the ultraviolet-visible (UV-Vis) spectral analysis demonstrates outstanding optical transparency (∼95%) of the deposited CuI films in the visible range. The current-voltage (I-V) and capacitance-voltage (C-V) analyses show that the p-type CuI layer is a vital and excellent charge generator and enhances the current density significantly. The tandem OLED device fabricated using Bphen:Liq/CuI/HAT-CN as the CGL results in a substantial 1.9-fold increase in current efficiency compared to the single-unit OLED device, approaching the theoretical two-fold increase. These findings highlight the potential of CuI as a promising p-type material for CGL design in tandem OLED devices.

Children face the excitement of a changing world but also encounter environmental threats to their health that were neither known nor suspected several decades ago. Children are at particular risk of exposure to pollutants that are widely dispersed in the air, water, and food. Children and adolescents are exposed to chemical, physical, and biological risks at home, in school, and elsewhere. Actions are needed to reduce these risks for children exposed to a series of environmental hazards. Exposure to a number of persistent environmental pollutants including air pollutants, endocrine disruptors, noise, electromagnetic waves (EMWs), tobacco and other noxious substances, heavy metals, and microplastics, is linked to damage to the nervous and immune systems and affects reproductive function and development. Exposure to environmental hazards is responsible for several acute and chronic diseases that have replaced infectious diseases as the principal cause of illnesses and death during childhood. Children are disproportionately exposed to environmental toxicities. Children drink more water, eat more food, and breathe more frequently than adults. As a result, children have a substantially heavier exposure to toxins present in water, food, or air than adults. In addition, their hand-to-mouth behaviors and the fact that they live and play close to the ground make them more vulnerable than adults. Children undergo rapid growth and development processes that are easily disrupted. These systems are very delicate and cannot adequately repair thetional development in children’s environmental health was the Declaration of the Environment Leaders of the Eight on Children’s Environmental Health by the Group of Eight. In 2002, the World Health Organization launched an initiative to improve children’s environmental protection effort. Here, we review major environmental pollutants and related hazards among children and adolescents.

BackgroundRelationship between recurrent wheeze and airway function and inflammation in preschool children is not fully known.ObjectiveTo investigate the relationship between recurrent wheeze and airway inflammation, lung function, airway hyper-reactivity (AHR) and atopy in preschool children.DesignObservational study, comparing forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and mid-forced expiratory flow (FEF25%–75%), dose–response slope (DRS), exhaled nitric oxide (eNO) and atopic sensitisation between children with recurrent wheeze and those without.SettingPopulation-based, cross-sectional study in Seoul and the Gyeonggi province of Korea conducted as a government-funded programme to perform standardised measurement of the prevalence of allergic diseases, and related factors, in preschool children.Participants900 children aged 4–6 years.Primary and secondary outcome measureseNO, FEV1/FVC, FEF25%–75%, DRS, atopic sensitisation and allergic diseases.MethodsChildren completed the modified International Study of Asthma and Allergies in Childhood questionnaire and underwent eNO assessments, spirometry, methacholine bronchial provocation tests and skin prick tests. Recurrent wheeze was defined as having a lifetime wheeze of more than three episodes, based on the questionnaire. The frequency of hospitalisation and emergency room visits was also obtained by means of the questionnaire. ‘Current’ wheeze was defined as having symptoms or treatments within the past 12 months.ResultsThe prevalence of recurrent wheeze was 13.4%. Children with recurrent wheeze showed a higher prevalence of lifetime or current allergic rhinitis (p=0.01 and p=0.002, respectively) and lifetime atopic dermatitis (p=0.007). Children with recurrent wheeze showed lower FEV1/FVC (p=0.033) and FEF25%–75% (p=0.004), and higher eNO levels (p=0.013) than those without recurrent wheeze. However, the DRS, prevalence of atopic sensitisation and serum IgE levels were not significantly different between the two groups.ConclusionsRecurrent wheeze in preschool children may be associated with airway inflammation and diminished airway function, but not with AHR or atopy.