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BackgroundEvidence regarding the effectiveness of contact tracing of COVID-19 and the related social distancing is limited and inconclusive. ObjectiveThis study aims to investigate the epidemiological characteristics of SARS-CoV-2 transmission in South Korea and evaluate whether a social distancing campaign is effective in mitigating the spread of COVID-19. MethodsWe used contract tracing data to investigate the epidemic characteristics of SARS-CoV-2 transmission in South Korea and evaluate whether a social distancing campaign was effective in mitigating the spread of COVID-19. We calculated the mortality rate for COVID-19 by infection type (cluster vs noncluster) and tested whether new confirmed COVID-19 trends changed after a social distancing campaign. ResultsThere were 2537 patients with confirmed COVID-19 who completed the epidemiologic survey: 1305 (51.4%) cluster cases and 1232 (48.6%) noncluster cases. The mortality rate was significantly higher in cluster cases linked to medical facilities (11/143, 7.70% vs 5/1232, 0.41%; adjusted percentage difference 7.99%; 95% CI 5.83 to 10.14) and long-term care facilities (19/221, 8.60% vs 5/1232, 0.41%; adjusted percentage difference 7.56%; 95% CI 5.66 to 9.47) than in noncluster cases. The change in trends of newly confirmed COVID-19 cases before and after the social distancing campaign was significantly negative in the entire cohort (adjusted trend difference –2.28; 95% CI –3.88 to –0.68) and the cluster infection group (adjusted trend difference –0.96; 95% CI –1.83 to –0.09). ConclusionsIn a nationwide contact tracing study in South Korea, COVID-19 linked to medical and long-term care facilities significantly increased the risk of mortality compared to noncluster COVID-19. A social distancing campaign decreased the spread of COVID-19 in South Korea and differentially affected cluster infections of SARS-CoV-2.

Rotavirus is linked to severe childhood gastroenteritis and neurological complications, but its impact on neurodevelopment remains uncertain. We examined data from 1 420 941 Korean children born between 2009 and 2011, using the Korean National Health Insurance System. We assessed neurodevelopmental outcomes at age 6 years using the validated Korean Developmental Test, covering 6 major domains, with propensity score-based inverse probability weighting including consideration of covariates sex, birth weight, changes in body weight from birth to 4–6 months of age, head circumference at 4–6 months of age, residence at birth, economic status, infant feeding types, and birth year. The main analysis that encompassed 5451 children with rotavirus hospitalization and 310 874 unexposed individuals revealed heightened odds of suspected delays in fine motor skills and cognition among exposed children. Our results suggest an association between rotavirus-related hospitalization in infancy and suspected delays in fine motor function and cognition in 6 year olds. [ABSTRACT FROM AUTHOR]

Viral lower respiratory tract infections (LRTIs), including rhinovirus and respiratory syncytial virus during early childhood, have been linked to subsequent asthma. However, the impact of other respiratory viruses remains unclear. We analyzed nationwide Korean data from January 1, 2008, to December 31, 2018, utilizing the national health insurance database. Our study focused on 19 169 meticulously selected children exposed to severe respiratory infections requiring hospitalization with documented viral pathogens, matched with 191 690 unexposed children at a ratio of 1:10 using incidence density sampling. Our findings demonstrate that asthma exacerbation rates were higher among the exposed cohort than the unexposed cohort over a mean follow‐up of 7.8 years. We observed elevated risks of asthma exacerbation and newly developed asthma compared to the unexposed cohort. Hospitalization due to rhinovirus, respiratory syncytial virus, influenza, metapneumovirus, and adenovirus was related to increased asthma exacerbations. Notably, we found a stronger association in cases of multiple LRTI hospitalizations. In conclusion, our study shows that early childhood respiratory viral infections are related to subsequent asthma exacerbations and new asthma diagnoses. [ABSTRACT FROM AUTHOR]

Introduction: This study examined the association between sugar-sweetened beverage consumption before the first 24 months of life and attention-deficit/hyperactivity disorder (ADHD). Methods: A population administrative cohort study was conducted in Korea (2008–2019) using linked national insurance data and a health screening survey. The cohort included 25,305 children in the exposed group with high sugar-sweetened beverage drinks (≥200 mL) and 339,931 in the reference groups (<200 mL) at 24 months of age. The primary outcome was the development of ADHD based on the International Classification of Disease (ICD) codes. Cox proportional model was used to identify the association between sugar-sweetened beverage consumption during early childhood and the later development of ADHD while controlling for multiple risk factors. Results: Over a mean follow-up period of 9.2 years, the incidence rates of ADHD were 29.6 and 23.8 per 10,000 person-years in the exposed and reference groups, respectively. Compared with the reference group, children consuming high-sugar drinks were at an increased risk of ADHD (adjusted hazard ratio 1.17, 95% confidence interval [CI] 1.08–1.27). These associations remained significant even after applying alternative ADHD definitions or adjusting for confounding variables. Conclusion: Children who consume sweetened beverages during early childhood are at increased risk of developing ADHD later in life. [ABSTRACT FROM AUTHOR]

We investigated the correlation between urine VOC metabolites and airway function in children exposed to anthropogenic volatile organic compounds (VOCs), notable pollutants impacting respiratory health. Out of 157 respondents, 141 completed skin prick tests, spirometry, IOS, and provided urine samples following the International Study of Asthma and Allergies in Childhood (ISAAC)-related questions. Allergic sensitization was assessed through skin prick tests, and airway functions were evaluated using spirometry and impulse oscillometry (IOS). Forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) was recorded and FEV1/FVC ratio was calculated. Airway mechanics parameters including respiratory resistance at 5 Hz (Rrs5) mean respiratory resistance between 5 Hz and 20 Hz (Rrs5–20), were also recorded. Urine concentrations of metabolites of benzene, ethylbenzene, toluene, xylene, styrene, formaldehyde, carbon-disulfide were analyzed by gas chromatography/tandem mass spectroscopy. The median age at study participation was 7.1 (SD 0.3) years. Muconic acid (benzene metabolites) and o-methyl-hippuric acid (xylene metabolites) above medians were associated with a significant increase in Rrs5 (muconic acid: aβ = 0.150, p =.002; o-methyl-hippuric acid: aβ = 0.143, p =.023) and a decrease in FEV1/FVC (o-methyl-hippuric acid: aβ = 0.054, p =.028) compared to those below median. No associations were observed for Rrs5–20 and FEV1 between the groups categorized as above and below the median (all parameter p values >.05). Elevated levels of benzene and xylene metabolites were associated with a significant increase in Rrs5 and a decrease in FEV1/FVC, related to increased resistance and restrictive lung conditions compared to individuals with concentrations below the median. [ABSTRACT FROM AUTHOR]

Background: Individuals with atopic dermatitis often develop other conditions. Objective: This study aimed to determine how atopic dermatitis comorbidities develop in children over time. Methods: This population‐based administrative cohort study used national health insurance data. We traced individuals born in Korea between 2002 and 2003 to 2018. The date of initial atopic dermatitis diagnosis was set as the index date. Fifty‐three childhood comorbidities of atopic dermatitis were identified as outcomes of interest by performing a comprehensive literature search and comparing the prevalence of diagnostic codes in children with and without atopic dermatitis. Four control children per individual in the atopic dermatitis group were randomly matched based on sex and index date. The association between atopic dermatitis and the development of each specified disease was assessed using proportional hazard assumption, followed by mapping of the temporal sequences of interconnected comorbidities. Results: The atopic dermatitis and control groups contained 67,632 and 270,528 individuals, respectively. The median age at the index date was 10 months, whereas the median follow‐up period was 15 years. Twenty diseases that were associated with a higher risk of atopic dermatitis were identified and a chain of interconnected conditions created. The progression began in childhood with febrile seizures, constipation, and asthma, and was later associated with the emergence of food allergy, allergic rhinitis, psychiatric disorders, and autoimmune diseases. Conclusion: Our study highlights the temporal nature of atopic dermatitis comorbidities in children, and indicates that an understanding of the comorbidities may inform its clinical management and treatment. [ABSTRACT FROM AUTHOR]

Background: Although atopic dermatitis (AD) in children affects diverse stages of life, no studies have reported on the association between school readiness and AD. Methods: This study used Korean National Health Insurance data and the Health Screening Program for Infants and Children. Among all children born between 2008 and 2012 in Korea, those who were assessed for school readiness through questionnaires in a health screening program performed at 54 and 60 months old were enrolled. AD was defined based on the International Classification of Diseases codes, with two or more prescriptions of topical corticosteroids during the first 54–60 months of life. The primary outcome was the association between school readiness and AD. The questionnaire relating to school readiness comprised six items – cognitive skills, social development, activeness, concentration, emotional development, and language skills. Logistic regression analysis was used to identify the associations between school readiness and AD. Results: This study included 239,673 children without AD and 38,229 children with AD. The average age at which school readiness was assessed was 4.8 years. AD was associated with vulnerability in activeness (adjusted odds ratio: 1.127; 95% confidence interval: 1.071–1.186) and concentrations (1.170; 1.093–1.254). The impact of AD on concentrations showed consistent results regardless of sex, exposure to systemic corticosteroids and antihistamines, and age at the diagnosis of AD. Conclusions: Children with AD have vulnerability in school readiness in the aspects of activeness and concentration. [ABSTRACT FROM AUTHOR]

Background: The optimal time of starting complementary foods (CFs) in infants remains a subject of debate. This population‐based longitudinal cohort study evaluated the association between early CF introduction and body mass index (BMI) in children aged 5–7 years. Methods: The present study included 917,707 children born in Korea during 2008–2009. Initial timing of CF introduction was obtained by questionnaires administered between 4 and 6 months and 9 and 12 months of age. The cohort consisted of 154,565 eligible individuals who properly completed the screening programme, including structured questionnaires, anthropometric measurements and physical examinations. To balance baseline characteristics, children were subjected to propensity score matching based on 95 covariates, including indicators of baseline health such as perinatal condition, birth weight, economic status, clinical disease and drug exposure. Exposure was defined as introduction to CF at age < 4 months, and outcomes were overweight (BMI z‐score > 85th percentile) and obesity (BMI z‐score > 95th percentile) at ages 5–7 years. Results: Of the 154,565 eligible children in the observed cohort, 10,499 (6.8%) were introduced to CF at age < 4 months and 144,066 (93.2%) at age ≥ 4 months. Propensity score matching yielded 9680 children introduced to CF at age < 4 months and 35,396 at age ≥ 4 months. The risk for being overweight or obese at age 5–7 years was slightly higher among those who started CF at age < 4 months than at age ≥4 months (adjusted relative risk = 1.06; 95% confidence interval = 1.02–1.09). A similar but stronger association was observed for being obese at age 5–7 years (adjusted relative risk = 1.12; 95% confidence interval = 1.05–1.19). Conclusions: Early CF introduction before age 4 months was associated with increased BMI at age 5–7 years. Key points: The optimal time of starting complementary foods (CFs) in infants remains a subject of debate.Early CF introduction before age 4 months was associated with increased body mass index (BMI) at age 5–7 years, which suggest that introducing CFs after 4 months as adherence to current guidelines is desirable regarding children's body mass.Physicians, parents, and caregivers of infants should be aware that early CF introduction is associated with increased childhood BMI. [ABSTRACT FROM AUTHOR]