Incidence, prevalence, and pattern of medical service utilization of children's rare lung diseases in South Korea.

INTRODUCTION: Children's rare lung diseases are a heterogeneous group of rare lung diseases with significant morbidity and mortality. There is very limited information on the incidence and prevalence of children's rare lung diseases in Asia. We investigated the nationwide incidence, prevalence, and pattern of medical service utilization of children's rare lung diseases in Korea. METHODS: We studied patients who were diagnosed with rare lung diseases coded per International Statistical Classification of Diseases and Related Health Problems, 10th Edition and registered in the national rare diseases database of confirmed patients. Data was extracted from the Korean National Health Insurance Service Claims database over 2019-2021. RESULTS: Average incidence rate was 12.9 new cases per million children per year, and average prevalence rate was 60.2 cases per million children during the study period of 2019-2021. We found that more than 65% of new cases were diagnosed before 2 years of age. ChILD, primary ciliary dyskinesia, and cystic fibrosis were usually diagnosed after 6 years of age. Congenital airway and lung anomalies were often diagnosed before 2 years of age. Busan and Gyeongsangnam-do residents tended to visit hospitals near their place of residence, while residents of other areas tended to visit hospitals in Seoul regardless of their area of residence. CONCLUSIONS: We examined the epidemiology of rare lung diseases in children in South Korea. Our estimation of the incidence and prevalence could be used for sustainable health care and equitable distribution of health care resources.

Atmospheric environment and persistence of pediatric asthma: A population-based cohort study.

BACKGROUND: Asthma is a heterogeneous disease with different outcomes. For children with asthma at the age of 7 years, 67-75% are symptom-free as adults. Data on the important link between childhood and adult asthma are sparse. OBJECTIVE: We aimed to investigate factors associated with persistence of childhood asthma over three years of follow-up by linking data between Korea childhood Asthma Study (KAS) and their matched claims data from Health Insurance Review and Assessment Service (HIRA). METHODS: We analyzed data from 450 preadolescent children aged 7 to 10 years and classified them into remission or persistence groups. Baseline clinical characteristics and exposure to air pollution materials including PM2.5 and PM10 during three years of follow-up were compared. The main outcome was asthma persistence which was defined as the presence of asthma episodes with healthcare utilization and prescription of asthma medications within three years after KAS enrollment. RESULTS: At the third year of follow-up, after stepwise regression analysis, lower age at enrollment (adjusted odds ratio (aOR): 0.79; 95% confidence interval (CI): 0.64-0.96), male sex (aOR: 1.66; 95%CI: 1.05-2.63), proximity from an air-polluting facility (aOR: 2.4; 95%CI: 1.34-4.29), higher level outdoor PM2.5 (aOR: 1.1; 95%CI: 1.02-1.20), and higher rate of doctor-diagnosed food allergy (FA) (aOR: 2.33; 95%CI: 1.06-5.12) were significantly associated with persistence. CONCLUSION: We discovered various independent risk factors for the persistence of childhood asthma. By linking HIRA claims data, we could clarify risk factors for persistence in a well-defined study population.

Evidence-based management guidelines for noncystic fibrosis bronchiectasis in children and adolescents.

Noncystic fibrosis bronchiectasis is a chronic respiratory disease that carries high socioeconomic and medical burdens and is caused by diverse respiratory illnesses. To improve clinical outcomes, early recognition, active treatment of exacerbations, and prevention of further exacerbations are essential. However, evidence for the treatment and prevention of acute exacerbation of noncystic fibrosis bronchiectasis, especially in children, is lacking. Therefore, the evidence- and consensus-based guidelines for medical and nonmedical treatment strategies for noncystic fibrosis bronchiectasis in children and adolescents were developed by the Korean Academy of Pediatric Allergy and Respiratory Disease using the methods recommended by the Grading of Recommendations Assessment, Development, and Evaluation working group with evidence published through July 2, 2020. This guideline encompasses evidence-based treatment recommendations as well as expert opinions, addressing crucial aspects of the treatment and management of noncystic fibrosis bronchiectasis in children. This includes considerations for antibiotics and airway clearance strategies, particularly in areas where evidence may be limited. Large, well-designed, and controlled studies are required to accumulate further evidence of management strategies for noncystic fibrosis bronchiectasis in children and adolescents.

Characteristics of febrile seizures with SARS-CoV-2 infection in the Omicron era.

Background: While the pandemic of coronavirus disease 2019 (COVID-19) is ongoing, the Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been dominant recently. The Omicron variant causes more seizures in pediatric patients compared with previously circulated variants. This study aimed to investigate the incidence and clinical features of febrile seizure (FS) in pediatric patients with COVID-19 during the Omicron era. Methods: The medical records of pediatric patients (≤18 years of age) diagnosed with COVID-19, who presented with FS between February 2020 and June 2022, were reviewed retrospectively to analyze clinical characteristics of FS in seven university-affiliated hospitals of Korea. Results: Of 664 pediatric patients with COVID-19 during the study period, 46 during the pre-Omicron period and 589 during the Omicron period were included in the study analysis; 29 patients during the transition period were excluded. Among the included patients, 81 (12.8%) had concomitant FS, and most (76.5%) experienced simple FS. All FS episodes occurred during the Omicron period and none of them during pre-Omicron period (P=0.016). Sixty-five (80.2%) and 16 (19.8%) patients were categorized as FS (patient age ≤60 months) and late-onset FS (patient age >60 months), respectively. Underlying neurologic disease (P=0.013) and focal onset seizure (P=0.012) were more common in the late-onset FS group than in the FS group; however, overall clinical manifestations and outcomes including seizures consistent with characteristics of complex FS and subsequent epilepsy were similar between the two groups. Conclusions: As the COVID-19 pandemic persists, the incidence of FS has increased with the emergence of the Omicron variant. About one-fifth of the patients experiencing FS due to infection by the Omicron variant of SARS-CoV-2 were aged >60 months; however, clinical characteristics and outcomes were favorable. More information and long-term prognoses in patients with FS due to COVID-19 should be acquired.

Fetal growth rather than prematurity determines lung function in children with asthma.

BACKGROUND AND OBJECTIVE: Preterm birth or fetal growth has been associated with reduced lung function and asthma during childhood in the general population. We aimed to elucidate whether prematurity or fetal growth has a significant influence on lung function or symptoms in children with stable asthma. METHODS: We included children with stable asthma who participated in the Korean childhood Asthma Study cohort. Asthma symptoms were determined by asthma control test (ACT). Percent predicted values of pre- and post-bronchodilator (BD) lung function including forced expiratory volume in 1 second (FEV1 ), forced vital capacity (FVC), and forced expiratory flow at 25%-75% of FVC (FEF25%-75% ) were measured. Lung function and symptoms were compared according to the history of preterm birth and birth weight (BW) for gestational age (GA). RESULTS: The study population consisted of 566 children (age range: 5-18 years). There were no significant differences in lung function and ACT between preterm and term subjects. We observed no significant difference in ACT but significant differences were observed in pre- and post-BD FEV1 , pre- and post-BD FVC, and post-BD FEF25%-75% according to BW for GA in total subjects. Two-way ANOVA revealed that BW for GA rather than prematurity was a significant determining factor for pre- and post-BD lung function. After regression analysis, BW for GA was still a significant determining factor of pre- and post-BD FEV1 and pre- and post-BD FEF25%-75% . CONCLUSION: Fetal growth rather than prematurity appears to have a significant effect on lung function in children with stable asthma.

Frequency of exacerbation and degree of required asthma medication can characterize childhood longitudinal asthma trajectories.

BACKGROUND: To the best of our knowledge, there have been no investigations of longitudinal asthma trajectories based on asthma exacerbation frequency and medications required for asthma control in children. OBJECTIVE: To investigate longitudinal asthma trajectories based on the exacerbation frequency throughout childhood and asthma medication ranks. METHODS: A total of 531 children aged 7 to 10 years were enrolled from the Korean childhood Asthma Study. Required asthma medications for control of asthma from 6 to 12 years of age and asthma exacerbation frequency from birth to 12 years of age were obtained from the Korean National Health Insurance System database. Longitudinal asthma trajectories were identified on the basis of asthma exacerbation frequency and asthma medication ranks. RESULTS: Four asthma clusters were identified: lesser exacerbation with low-step treatment (8.1%), lesser exacerbations with middle-step treatment (30.7%), highly frequent exacerbations in early childhood with small-airway dysfunction (5.7%), and frequent exacerbations with high-step treatment (55.6%). The frequent exacerbations with high-step treatment cluster were characterized by a high prevalence of male sex, increased blood eosinophil (counts) with fractional exhaled nitric oxide, and high prevalence of comorbidities. The highly frequent exacerbation in early childhood with small-airway dysfunction cluster was characterized by recurrent wheeze in preschool age, with high prevalence of acute bronchiolitis in infancy and a greater number of family members with small-airway dysfunction at school age. CONCLUSION: The present study identified 4 longitudinal asthma trajectories on the basis of the frequency of asthma exacerbation and asthma medication ranks. These results would help clarify the heterogeneities and pathophysiologies of childhood asthma.

Impulse oscillometry system for assessing small airway dysfunction in pediatric bronchiolitis obliterans; association with conventional pulmonary function tests.

Impulse oscillometry system (IOS) is a simple, and less invasive method for assessing small to total airway resistance in children. We analyzed the correlation between IOS, spirometry, and plethysmographic parameters performed for the diagnosis of pediatric BO patients. A total of 89 IOS assessments of pediatric BO patients or children without lung disease were included, and the relationship between pulmonary function tests (PFTs) and diagnostic performance was analyzed. R5, R5-20, X5, and AX were statistically significantly worse in the BO group. In general linear correlation analysis, R5% (adjusted ß [aß], -0.59; p < 0.001) and AX % (aß, -0.9; p < 0.001) showed the strongest correlation with conventional PFT parameters. R5% and AX % also showed the highest correlation with FEF25-75% (aß, -0.48; p < 0.001 and aß, -0.83; p < 0.001), and sRaw % (aß, -0.73; p = 0.003 and aß, -0.59; p = 0.008, respectively). Multivariate logistic regression analysis showed that R5 Z-score showed the highest ORs with FEV1 (OR = 3.94, p = 0.006), FEF25-75% (OR = 5.96, p = 0.005), and sRaw % (OR = 4.85, p = 0.022). Receiver operating curve analysis suggested AX % and R5% as the most optimal IOS parameters for BO diagnostic performance with the area under the curve of 0.915 and 0.882, respectively. In conclusion, R5 and AX are the parameters that can independently identify the severity of airway obstruction in pediatric BO patients without conventional lung function tests. IOS is an easy-to-perform, and reliable diagnostic method capable of detecting pathological obliteration of the small airways in children with BO.

Efficacy and Safety of Low-Dose Cyclosporine Relative to Immunomodulatory Drugs Used in Atopic Dermatitis: A Systematic Review and Meta-Analysis.

Cyclosporine A (CsA) is effective in treating moderate-to-severe atopic dermatitis (AD). This systematic review and meta-analysis aimed to summarize the effectiveness and safety of low-dose (<4 mg/kg) versus high-dose (≥4 mg/kg) CsA and other systemic immunomodulatory agents in patients with AD. Five randomized controlled trials met the inclusion criteria. The meta-analysis included 159 patients with moderate-to-severe AD who were randomized to receive low-dose CsA, and 165 patients randomized to receive high-dose CsA and other systemic immunomodulatory agents. We found that low-dose CsA was not inferior to high-dose CsA and other systemic immunomodulatory agents in reducing AD symptoms [standard mean difference (SMD) -1.62, 95% confidence interval (CI) -6.47; 3.23]. High-dose CsA and other systemic immunomodulatory agents showed a significantly lower incidence of adverse events [incidence rate ratio (IRR) 0.72, 95% CI 0.56; 0.93], however, after sensitivity analysis, there was no difference between the two groups except for one study (IRR 0.76, 95% CI 0.54; 1.07). Regarding serious adverse events requiring discontinuation of treatment, we observed no significant differences between low-dose CsA and other systemic immunomodulatory agents (IRR 1.83, 95% CI 0.62; 5.41). Our study may justify the use of low-dose CsA rather than high-dose CsA and other systemic immunomodulatory agents in moderate-to-severe AD.

Changes in the Clinical Characteristics of Kawasaki Disease After Coronavirus Disease (COVID-19) Pandemic: A Database Analysis.

BACKGROUND: The impact of the coronavirus disease 2019 (COVID-19) pandemic on Kawasaki disease (KD) has not yet been established. We investigated changes in the observed number and severity of KD cases and accompanying coronary artery complications during the COVID-19 pandemic in Korea. METHODS: This retrospective observational study included patients aged < 18 years with acute-phase KD diagnosed between March 2018 and February 2021. Data were extracted from the Clinical Data Warehouse that houses data from five affiliated university hospitals in Korea. We analyzed changes in the number of patient admissions and clinical characteristics, including cardiac complications, before and after the onset of the COVID-19 pandemic. RESULTS: A total of 475 admissions were included in the analysis. After March 2020, we observed a significant decrease of 33% in the number of hospitalizations for KD compared with the average number of hospitalizations during the previous 2 years. The number of admissions per month significantly decreased by 7.9 persons/month (95% confidence interval, -13.8 to -2.0; P < 0.05) compared with that before COVID-19. By contrast, the proportion of patients aged < 1 year with KD increased. The proportion of patients with refractory KD and the rate of cardiac complications did not change significantly. CONCLUSION: Since the onset of the COVID-19 pandemic, the total number of hospital admissions for KD has decreased in Korea. Although the proportion of admissions of infants aged < 1 year increased, no changes were observed in clinical courses and complications.

Longitudinal asthma exacerbation phenotypes in the Korean childhood asthma study cohort.

BACKGROUND: Asthma exacerbation (AE) leads to social and economic costs and long-term adverse outcomes. We aimed to predict exacerbation-prone asthma (EPA) in children. METHODS: The Korean childhood Asthma Study (KAS) is a prospective nationwide pediatric asthma cohort of children aged 5-15 years followed every 6 months. Patients with AE during the 6 months prior to all three visits, with AE prior to one or two visits, and without AE prior to any visit were defined as having EPA, exacerbation-intermittent asthma (EIA), and exacerbation-resistant asthma (ERA), respectively. Risk factors and prediction models of EPA were explored. RESULTS: Of the 497 patients who completed three visits, 42%, 18%, and 15% had exacerbations prior to visits 1, 2, and 3 and 5%, 47%, and 48% had EPA, EIA, and ERA, respectively. Univariate and multivariable logistic regression revealed forced expiratory volume in 1 s (FEV1) z-score, forced vital capacity (FVC) z-score, white blood cell (WBC) count, and asthma control test (ACT) score as relevant EPA risk factors. The EPA prediction model comprised FVC z-score, WBC count, ACT score, sex, and parental education level (area under the receiver operating characteristic curve [AUROC] 0.841 [95% confidence interval (CI): 0.728-0.954]). CONCLUSION: With appropriate management, AE decreases over time, but persistent AEs may occur. Apart from asthma control level, baseline lung function and WBC count predicted EPA.

Eosinophil-derived neurotoxin: An asthma exacerbation biomarker in children.

Background: Asthma is a heterogeneous disease, characterized by chronic airway inflammation. Asthma exacerbations (AE) are episodes characterized by a progressive increase in symptoms of shortness of breath, cough, wheezing, or chest tightness with a decrease in lung function. There have been previous studies that examined the role of eosinophil-derived neurotoxin (EDN) in asthma, but there have been no studies of the role of EDN in children experiencing AE. Objective: In this study, we aimed to examine the association of EDN with lung function and prognosis in children admitted for severe AE. Methods: We enrolled 82 children who were admitted for severe AE at two different university hospitals in South Korea between January 2018 and December 2019. Blood tests, including white blood cell count, myeloperoxidase (MPO), total eosinophil count, EDN, C-reactive protein (CRP) level, and interleukin (IL) 4, IL-5, IL-10 values, and lung function were measured on admission and at discharge in each patient. Results: We observed significant decreases in the levels of MPO, EDN, CRP, and IL-4, with significant improvement in lung function after treatment. We then classified the subjects into two groups of different clinical phenotypes: eosinophilic asthma exacerbation (EAE) group and non-EAE group. EDN levels were higher and lung functions were lower in the EAE group. Also, we found that the EDN level was a significant biomarker useful for predicting the number of days for hospital stay. Conclusion: We found that EDN can act as a biomarker that reflects lung function, and that EDN could act as a prognostic biomarker, which demonstrated the complex role of EDN in children experiencing AE.

Level of interleukin-18 binding protein is significantly different in patients with anaphylaxis than urticaria.

BACKGROUND: Acute urticaria is a common cutaneous disease encountered in children, while anaphylaxis can show cutaneous symptoms as well as systemic symptoms. One study found that urticaria tends to precede anaphylaxis, but studies on the different role of eosinophils and related cytokines in anaphylaxis and urticaria are lacking. OBJECTIVE: The aim of this study was to compare the clinical features, total eosinophil count, serum levels of interleukin (IL)-18, IL-18 binding protein (BP), IL-1 receptor-like (RL) 1, and IL-33 and compare with tryptase to examine if any differences could be found between patients who experienced anaphylaxis and urticaria. METHODS: We included 63 patients with urticaria and 52 patients with anaphylaxis. We measured total eosinophil count and the serum levels of total IgE, tryptase, IL-18, IL-18BP, IL-1RL1, and IL-33, and we compared the differences between the groups. Lastly, receiver operating characteristic curves were constructed to determine which factors accurately diagnosed anaphylaxis. RESULTS: No significant differences were observed in the clinical characteristics or sensitization between urticaria group and anaphylaxis group. Laboratory findings showed that total eosinophil count and IL-18BP were significantly lower in the anaphylaxis group, compared with the urticaria group. IL-18BP showed significant correlation with tryptase. The receiver operating characteristic curve for IL-18BP for diagnosing anaphylaxis had an area under the curve of 0.530. CONCLUSIONS: IL-18BP level was significantly different in patients with anaphylaxis compared to those with urticaria. Serum IL-18BP level may be used to differentiate between the patients with urticaria or anaphylaxis.

Long-term macrolide treatment for non-cystic fibrosis bronchiectasis in children: a meta-analysis.

Recurrent bacterial infection causes frequent bronchiectasis (BE) exacerbations. The effectiveness and safety of long-term administration of macrolides in BE remain controversial, especially in children who require minimal treatment to prevent exacerbation. We conducted this meta-analysis to determine the usefulness of long-term macrolide use in pediatric BE. We searched PubMed, Cochrane Library databases, Embase, KoreaMed, Igaku Chuo Zasshi, and Chinese National Knowledge Infrastructure databases. We identified randomized controlled trials (RCTs) which elucidated long-term macrolide treatment (≥ 4 weeks) in non-cystic fibrosis BE in children aged < 18 years. The primary outcome was frequency of acute exacerbation; secondary outcomes included changes in pulmonary function, sputum scores, and adverse events including bacterial resistance. We included four RCTs. Long-term macrolide treatment showed a significant decrease in the frequency of exacerbation (odds ratio [OR], 0.30; 95% confidence interval [CI], 0.10-0.87), mean number of exacerbations per patient (mean difference, - 1.40; 95% CI, - 2.26 to - 0.54), and sputum purulence score (mean difference, - 0.78; 95% CI, - 1.32 to - 0.24). However, long-term macrolide treatment was accompanied by an increased carriage of azithromycin-resistant bacteria (OR, 7.13). Long-term macrolide administration prevents exacerbation of BE in children; however, there are risks of increasing antibiotic resistance. Benefits and risks should be weighed and determined on a patient-by-patient basis.

Heterogeneity of Childhood Asthma in Korea: Cluster Analysis of the Korean Childhood Asthma Study Cohort.

PURPOSE: Asthma is a heterogeneous airway disease occurring in children, and it has various clinical phenotypes. A clear differentiation of the clinical phenotypes can provide better asthma management and prediction of asthma prognosis. Little is currently known about asthma phenotypes in Korean children. This study was designed to identify asthma phenotypes in school-aged Korean children. METHODS: This study enrolled 674 children with physician-diagnosed asthma from the Korean childhood Asthma Study (KAS) cohort. The physicians verified the relevant histories of asthma and comorbid diseases, as well as airway lability and hyper-responsiveness from the results of pulmonary function tests and bronchial provocation tests. Questionnaires regarding the participants' baseline characteristics, their environment and self-rating of asthma control were collected at the time of enrollment. Laboratory tests were performed to assess allergy and airway inflammation. Children with asthma were classified by hierarchical cluster analysis. RESULTS: Of the 674 patients enrolled from the KAS cohort, 447 were included in the cluster analysis. Cluster analysis of these 447 children revealed 4 asthma phenotypes: cluster 1 (n = 216, 48.3%) which was characterized by male-dominant atopic asthma; cluster 2 (n = 79, 17.7%) which was characterized by early-onset atopic asthma with atopic dermatitis; cluster 3 (n = 47, 10.5%) which was characterized by puberty-onset, female-dominant atopic asthma with the low lung function; and cluster 4 (n = 105, 23.5%) which was characterized by early-onset, non-atopic dominant asthma. CONCLUSIONS: The asthma phenotypes among Korean children can be classified into 4 distinct clusters. Long-term follow-up with these phenotypes will be needed to define their prognosis and response to treatment.

Recent advances in mast cell activation and regulation.

Mast cells are innate immune cells that intersect with the adaptive immunity and play a crucial role in the initiation of allergic reactions and the host defense against certain parasites and venoms. When activated in an allergen- and immunoglobulin E (IgE)-dependent manner, these cells secrete a large variety of allergenic mediators that are pre-stored in secretory granules or de novo-synthesized. Traditionally, studies have predominantly focused on understanding this mechanism of mast cell activation and regulation. Along this line of study, recent studies have shed light on what structural features are required for allergens and how IgE, particularly anaphylactic IgE, is produced. However, the last few years have seen a flurry of new studies on IgE-independent mast cell activation, particularly via Mrgprb2 (mouse) and MRGPRX2 (human). These studies have greatly advanced our understanding of how mast cells exert non-histaminergic itch, pain, and drug-induced pseudoallergy by interacting with sensory neurons. Recent studies have also characterized mast cell activation and regulation by interleukin-33 (IL-33) and other cytokines and by non-coding RNAs. These newly identified mechanisms for mast cell activation and regulation will further stimulate the allergy/immunology community to develop novel therapeutic strategies for treatment of allergic and non-allergic diseases.

Asthma control test reflects not only lung function but also airway inflammation in children with stable asthma.

Objective: Various numerical asthma control tools have been developed to distinguish different levels of symptom control. We aimed to examine whether the asthma control test (ACT) is reflective of objective findings such as lung function, fractional exhaled nitric oxide (FeNO) and laboratory data in patients with stable asthma.Methods: We included patients who were enrolled in the Korean Childhood Asthma Study. ACT, spirometry, blood tests and FeNO were performed in patients after stabilization of their asthma. We examined differences among spirometry parameters, blood tests and FeNO according to control status as determined by ACT and investigated for any significant correlations.Results: The study population consisted of 441 subjects. Spirometry showed that forced expiratory volume in one second (FEV1), forced expiratory flow between 25% and 75% of forced vital capacity and FEV1/forced vital capacity were all significantly higher in the controlled asthma group. Likewise, FeNO and percent-change in FEV1 were both significantly lower in the controlled asthma group. In blood tests, the eosinophil fraction was significantly lower in the controlled asthma group while white blood cell count was significantly higher in the controlled asthma group. Lastly, among the various factors analyzed, only provocative concentration of methacholine causing a 20% fall in FEV1 significantly correlated with ACT score.Conclusion: ACT is useful as part of the routine evaluation of asthmatic children and should be used as a complement to existing tools such as spirometry and FeNO measurement.

Effect of multi-ethnicity and ancestry on prevalence of allergic disease.

BACKGROUND/PURPOSE: Differences exist among racial and ethnic groups in the prevalence and severity of allergic diseases. However, influence of population admixing on allergic disease has not been studied. We examined the effect of population admixing on the occurrence of allergic disease. METHODS: We reviewed the data of 68,043 adolescents who participated in the 11th Korea Youth Risk Behavior Web-based Survey, which provides a sample that is representative of the entire Korean middle school and high school student population. Multi-ethnic status was determined by using parental country of birth and prevalence of asthma, allergic rhinitis (AR), and atopic dermatitis (AD) was determined by questionnaire. RESULTS: Multi-ethnic adolescents accounted for approximately 0.9% of the total adolescents. Prevalence of asthma was significantly higher in multi-ethnic group than non multi-ethnic group while that of AR and AD was significantly higher in non multi-ethnic group than multi-ethnic group. Parental region of country at birth showed a significant difference in prevalence of allergic disease. Univariate analysis found that urbanity, perceived economic status (PES), parental region of country at birth, and environmental tobacco smoke (ETS) showed a significant odds ratio (OR) in asthma, AR, and AD. Body mass index (BMI) showed a significant OR in asthma and AD. After adjusting for urbanity, PES, BMI and ETS, multiethnicity showed significantly lower OR in AR and AD. CONCLUSION: Population admixing appears to have significant effect on the prevalence of allergic disease. Further study will be needed to clarify the effect of population admixing on prevalence of allergic disease.

Associated Factors for Asthma Severity in Korean Children: A Korean Childhood Asthma Study.

PURPOSE: Childhood asthma has a considerable social impact and economic burden, especially in severe asthma. This study aimed to identify the proportion of childhood asthma severity and to evaluate associated factors for greater asthma severity. METHODS: This study was performed on 667 children aged 5-15 years with asthma from the nationwide 19 hospitals in the Korean childhood Asthma Study (KAS). Asthma was classified as mild intermittent, mild persistent, and moderate/severe persistent groups according to the National Asthma Education and Prevention Program recommendations. Multinomial logistic regression models were used to identify the associated factors for greater asthma severity. RESULTS: Mild persistent asthma was most prevalent (39.0%), followed by mild intermittent (37.6%), moderate persistent (22.8%), and severe persistent asthma (0.6%). Onset later than 6 years of age (adjusted odds ratio [aOR], 1.69 for mild persistent asthma; aOR, 1.92 for moderate/severe persistent asthma) tended to increase asthma severity. Exposure to environmental tobacco smoke (aOR, 1.53 for mild persistent asthma; aOR, 1.85 for moderate/severe persistent asthma), and current dog ownership with sensitization to dog dander (aOR, 5.86 for mild persistent asthma; aOR, 6.90 for moderate/severe persistent asthma) showed increasing trends with greater asthma severity. Lower maternal education levels (aOR, 2.32) and no usage of an air purifier in exposure to high levels of outdoor air pollution (aOR, 1.76) were associated with moderate/severe persistent asthma. CONCLUSIONS: Modification of identified environmental factors associated with greater asthma severity might help better control childhood asthma, thereby reducing the disease burden due to childhood asthma.