Association between the COVID-19 pandemic and childhood development aged 30 to 36 months in South Korea, based on the National health screening program for infants and children database.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has had a significant impact on the neurodevelopment of children. However, the precise effects of the virus and the social consequences of the pandemic on pediatric neurodevelopment are not yet fully understood. We aimed to compare the neurodevelopment of children between before and during the COVID-19 pandemic, as well as examine the impact of socioeconomic status (SES) and regional differences on the development. METHODS: The study used the Korean Developmental Screening Test to compare the difference in the risk of neurodevelopmental delay between before and during the COVID-19 pandemic. Multivariable logistic regression analysis was conducted to identify the relationship between experiencing the COVID-19 pandemic and the risk of neurodevelopmental delay. Stratified analyses were performed to determine whether the developmental delays caused by the pandemic's impact varied depending on SES or regional inequality. RESULTS: This study found an association between the experience of COVID-19 and a higher risk of neurodevelopmental delay in communication (adjusted OR [aOR]: 1.21, 95% confidence interval [CI]: 1.19, 1.22; P-value: < 0.0001) and social interaction (aOR: 1.15, 95% CI: 1.13, 1.17; P-value: < 0.0001) domains among children of 30-36 months' ages. Notably, the observed association in the Medicaid group of children indicates a higher risk of neurodevelopmental delay compared to those in the non-Medicaid group. CONCLUSIONS: These findings highlight the need to be concerned about the neurodevelopment of children who experienced the COVID-19 pandemic. The study also calls for increased training and support for Medicaid children, parents, teachers, and healthcare practitioners. Additionally, policy programs focused on groups vulnerable to developmental delays are required.

Impact of the Early COVID-19 Pandemic on Emergency Department Visits of Adult Cancer Patients With Fever or Respiratory Symptoms: A Korean Nationwide Population-Based Study, 2016-2020.

BACKGROUND: We performed a nationwide analysis to evaluate the impact of the early coronavirus disease 2019 (COVID-19) pandemic on emergency department (ED) visits by adult cancer patients having COVID-like symptoms. METHODS: We analyzed the National Emergency Department Information System (NEDIS) data on ED visits by adult cancer patients who presented with chief complaints of fever or respiratory symptoms (FRS) indicative of COVID-19, from 2016 to 2020. An interrupted time series analysis with a quasi-Poisson regression model was performed, adjusting for seasonality and time, to evaluate whether underlying trends for monthly ED visits and the in-hospital mortality rate (%) per month changed with the pandemic among these patients. We also estimated the adjusted odds ratio (aOR) of in-hospital deaths among cancer patients using multivariable logistic regression analysis. RESULTS: ED visits by cancer patients with FRS decreased during the COVID-19 pandemic (relative risk [RR] with 95% confidence interval [CI]: slope change, 0.99 [0.98-1.00] and step change, 0.84 [0.76-0.92]). However, the in-hospital mortality rate (%) for these patients was increased (slope change, 1.14 [1.04-1.25] and step change, 0.99 [0.98-1.01]). Factors such as urgent triage status, ambulance use, and treatment in hospitals with fewer than 300 staffed beds significantly contributed to increased aOR of in-hospital deaths during the COVID-19 pandemic compared to the pre-pandemic period. CONCLUSION: Further studies are needed to highlight the importance of ED service preparation in planning and managing resources for cancer patients during future pandemics.

COVID-19 and Neurodevelopmental Delays in Early Childhood: A Longitudinal Analysis of Developmental Outcomes in Korean Children.

This study employed a longitudinal analysis to evaluate the association between the coronavirus disease 2019 pandemic and neurodevelopment by analyzing over 1.8 million children from the Korean Developmental Screening Test for Infants and Children included in South Korea's National Health Screening Program. We compared the developmental outcomes in five age groups-9-17 months, 18-29 months, 30-41 months, 42-53 months, and 54-65 months-between the pre-pandemic (2018-2019) and pandemic (2020-2021) periods. Significant increases in potential developmental delays were observed during the pandemic in communication, cognitive, social interaction, self-care, and fine motor skills across most age groups. All five age groups experienced notable disruptions in communication and fine motor skills. Children from socioeconomically disadvantaged backgrounds faced higher risks across all domains. These findings highlight the need for targeted interventions and continuous monitoring to support the developmental needs of children affected by pandemic-related disruptions.

Impact of the early phase of the COVID-19 pandemic on emergency department-to-intensive care unit admissions in Korea: an interrupted time-series analysis.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic resulted in significant disruptions to critical care systems globally. However, research on the impact of the COVID-19 pandemic on intensive care unit (ICU) admissions via the emergency department (ED) is limited. Therefore, this study evaluated the changes in the number of ED-to-ICU admissions and clinical outcomes in the periods before and during the pandemic. METHODS: We identified all adult patients admitted to the ICU through level 1 or 2 EDs in Korea between February 2018 and January 2021. February 2020 was considered the onset point of the COVID-19 pandemic. The monthly changes in the number of ED-to-ICU admissions and the in-hospital mortality rates before and during the COVID-19 pandemic were evaluated using interrupted time-series analysis. RESULTS: Among the 555,793 adult ED-to-ICU admissions, the number of ED-to-ICU admissions during the pandemic decreased compared to that before the pandemic (step change, 0.916; 95% confidence interval [CI] 0.869-0.966], although the trend did not attain statistical significance (slope change, 0.997; 95% CI 0.991-1.003). The proportion of patients who arrived by emergency medical services, those transferred from other hospitals, and those with injuries declined significantly among the number of ED-to-ICU admissions during the pandemic. The proportion of in-hospital deaths significantly increased during the pandemic (step change, 1.054; 95% CI 1.003-1.108); however, the trend did not attain statistical significance (slope change, 1.001; 95% CI 0.996-1.007). Mortality rates in patients with an ED length of stay of ≥ 6 h until admission to the ICU rose abruptly following the onset of the pandemic (step change, 1.169; 95% CI 1.021-1.339). CONCLUSIONS: The COVID-19 pandemic significantly affected ED-to-ICU admission and in-hospital mortality rates in Korea. This study's findings have important implications for healthcare providers and policymakers planning the management of future outbreaks of infectious diseases. Strategies are needed to address the challenges posed by pandemics and improve the outcomes in critically ill patients.

Temporal Trends and Characteristics of Adult Patients in Emergency Department Related to Suicide Attempt or Self-Harm in Korea, 2016-2020.

BACKGROUND: The implementation of an effective suicide prevention program requires the identification and monitoring of subpopulations with elevated risks for suicide in consideration of demographic characteristics, to facilitate the development of tailored countermeasures for tackling the risk factors of suicide. We examined the annual trends in emergency department (ED) visits for suicide attempts (SAs) or self-harm and investigated the sex- and age-specific characteristics of individuals who visited the ED for SA and self-harm. METHODS: Data on ED visits for SAs or self-harm in Korea from 2016 to 2020 were extracted from the National Emergency Department Information System and assessed. We evaluated the age-standardized incidence rate of ED visits for SAs or self-harm, and hospital mortality among individuals who visited the ED for SAs or self-harm. In addition, the characteristics of the individuals were compared according to sex and age. RESULTS: We identified 145,963 ED visits for SAs or self-harm (0.42% of the total ED visits) during the study period. The rate of ED visits increased in the youngest age group (19-29 years old), and was more prominent among women (increased by an annual average of 22.5%), despite the coronavirus disease pandemic. The middle-aged group (45-64 years old) had a higher rate of mortality than other age groups, and the highest proportion of individuals on Medical Aid. CONCLUSION: It is necessary to plan age- and gender-specific suicide prevention programs that focus on improving the limited public mental health resources for the vulnerable populations.

Real-World Effectiveness of Nirmatrelvir-Ritonavir and Its Acceptability in High-Risk COVID-19 Patients.

BACKGROUND: Nirmatrelvir-ritonavir is highly effective in preventing severe coronavirus disease 2019 (COVID-19) in high-risk patients with mild-to-moderate severity. However, real-world performance data are limited, and the drug is not so acceptable to the COVID-19 patients at high risk who need it in Korea. METHODS: To evaluate the effectiveness of nirmatrelvir-ritonavir, we conducted a propensity score-matched retrospective cohort study on patients with mild-to-moderate COVID-19 at high risk for a severe disease who were hospitalized at four hospitals in South Korea from February 2022 to April 2022. A total of 236 patients in the treatment group (administered nirmatrelvir-ritonavir) and 236 in the matched control group (supportive care only) were analyzed for the primary outcome, i.e., the time to oxygen support-free survival. The secondary outcome was a composite result of disease progression. The reason for not prescribing nirmatrelvir-ritonavir to the indicated patients was also investigated. RESULTS: The treatment group showed significantly longer oxygen support-free survival than the matched control group (adjusted hazard ratio [aHR], 0.07; 95% confidence interval [CI], 0.01-0.31; P < 0.001). Multivariate Cox regression analysis showed that age (aHR, 1.03; 95% CI, 1.00-1.07), National Early Warning Score-2 at admission (aHR, 1.36; 95% CI, 1.08-1.71), nirmatrelvir-ritonavir treatment, female sex (aHR, 0.37; 95% CI, 0.15-0.88), and time from symptom onset to admission (aHR, 0.67; 95% CI, 0.48-0.95) were significantly associated with oxygen therapy. However, none of the factors were related to the composite outcome. In the unmatched control group, 19.9% of 376 patients had documented explanations for nirmatrelvir-ritonavir non-prescription, and 44.0% of these were due to contraindication criteria. In the treatment group, 10.9% of patients discontinued the medication primarily because of adverse events (71.4%), with gastrointestinal symptoms being the most common (50.0%). CONCLUSION: Nirmatrelvir-ritonavir treatment significantly reduced oxygen therapy requirements in high-risk patients with COVID-19 during the omicron variant surge in South Korea. Physicians are encouraged to consider the active use of nirmatrelvir-ritonavir and to be watchful for gastrointestinal symptoms during medication.

Dietary patterns are associated with attention-deficit hyperactivity disorder (ADHD) symptoms among preschoolers in South Korea: a prospective cohort study.

OBJECTIVES: Attention-deficit hyperactivity disorder (ADHD) is a prevalent neurobehavioral disorder in children. There are limited studies for diet or dietary supplement effects on ADHD in preschool children in Asia. This study aimed to determine the association between dietary patterns in 4-year-old children and ADHD symptoms in 6-year-old children. METHODS: We estimated dietary intake in 4-year-old children using a food frequency questionnaire. Using 33 food groups, major dietary patterns were identified in relation to the consumption of sweets, vegetables, meats, and carbohydrates. Parents of 6-year-old children used the Korean version of the ADHD Rating Scale for ADHD symptom assessment. RESULTS: A sweet dietary pattern was associated with a higher risk of attention deficit (AD) (relative risk [RR], 1.34; confidence interval [CI], 1.17-1.55), hyperactivity (RR, 1.40; CI, 1.19-1.64), and ADHD symptoms (RR, 1.37; CI, 1.23-1.52). A vegetable dietary pattern was associated with a lower risk of ADHD symptoms (RR, 0.81; CI, 0.72-0.90). Food item analysis of the sweet dietary pattern showed that intake scores for chocolate, chips, and fruit jams positively correlated with AD, hyperactivity, and ADHD symptoms. DISCUSSION: These findings can be useful to further understand the roles of dietary factors in ADHD.

Suicide attempt-related emergency department visits among adolescents: a nationwide population-based study in Korea, 2016-2019.

BACKGROUND: The incidence of adolescent suicide in Korea is increasing; however, nationwide data regarding short-term prediction of suicide attempts (SAs) is still limited. Therefore, this study aimed to investigate the incidence of SA-related annual emergency department (ED) visits among adolescents in Korea from 2016 to 2019 and to summarize the corresponding demographic and clinical characteristics based on the dispositions of SA-related ED visits. METHODS: Most referral hospitals provide relevant essential ED information to the National Emergency Medical Center through the National Emergency Department Information System (NEDIS). We analyzed NEDIS data on adolescent visits (aged < 20 years) for a 4-year period from 2016 to 2019. Patients were classified into the discharge and hospitalization groups for comparison, and jointpoint regression analysis was used to identify the years in which there was a change in annual percentage change (APC) in age- and sex-standardized incidence rates of SA-related ED visits. The characteristics of patients in the discharge group and hospitalization group subgroups were also compared. RESULTS: The APC in the incidence rate of SA-related ED visits in the 4-year study period revealed a 35.61% increase. The incidence rate increase was higher among females (APC: 46.26%) than among males (APC: 17.95%). Moreover, the incidence rate increased faster in mid-adolescence patients (APC: 51.12%) than in late-adolescence patients (APC: 26.98%). The proportion of poisoning as the SA method was 69.7% in the hospitalization group and 34.5% in the discharge group (p < 0.001). DISCUSSION: Our findings suggest that an increase in the number of SA-related ED visits among female and mid-adolescent patients represented the largest increase in SA-related ED visits from 2016 to 2019. Accordingly, evidence-based suicide prevention programs need to be customized based on sex and age, and further diversification of health care systems is needed through analysis of the characteristics of the dispositions of SA-related ED visits.

Association Between Sleep Duration and Intelligence Quotient in 6-Year-Old Children.

BACKGROUND: Sufficient sleep during childhood is important for cognitive functions such as learning and successful school performance. This study aimed to investigate the effects of sleep duration on the intelligence quotient (IQ) of 6-year-old children and aimed to analyze whether these effects differed by sex. METHODS: The IQ of 538 6-year-old Korean participants from the cohort study, "The Environment and Development of Children," was measured during follow-up using the Korean Educational Developmental Institute's Wechsler Intelligence Scale for Children. The total, verbal, and performance IQ scores were evaluated. The relationship between sleep duration and IQ scores after adjusting for maternal age, maternal educational level, maternal occupation, maternal IQ, exposure to secondhand smoking, gestational age, and monthly age and birth season was also assessed. RESULTS: Longer sleep duration was significantly associated with improved verbal IQ measures (ß 0.55; p value 0.030). After stratifying participants by sex, a significant association was observed between sleep duration and total, verbal, and performance IQ scores in boys (total IQ 2.49, p value 0.012; verbal IQ 0.75, p value: 0.037; performance IQ 0.73, p value 0.048), but not in girls. CONCLUSIONS: The results indicated that only boys show a significant association between IQ scores and sleep duration. These findings support the hypothesis that sleep duration is associated with IQ, in a sex dependent manner. Future studies are needed for a thorough evaluation of the connection between sleep duration and health outcome in young children.

Factors Related to Anxiety and Depression Among Adolescents During COVID-19: A Web-Based Cross-Sectional Survey.

BACKGROUND: The coronavirus disease 2019 (COVID-19) outbreak and subsequent disease-containment measures (such as school closures) significantly affected the lives of adolescents. We evaluated the mental-health status and factors associated with anxiety and depression among South Korean adolescents. METHODS: A nationwide online survey was conducted to evaluate the mental-health status of South Korean adolescents during the COVID-19 pandemic. In total, 570 adolescents aged 13-18 years were surveyed between May 27 and June 11, 2021. The participants completed the Generalized Anxiety Disorder Scale (GAD-7) and Patient Health Questionnaire (PHQ-9) to determine anxiety and depression symptoms, respectively. Stepwise logistic regression models were constructed to determine factors related to anxiety and depression. RESULTS: Among the study participants, 11.2% and 14.2% had anxiety and depression, respectively. The results suggested that several factors, such as the experience of COVID-19 infection and quarantine of oneself, a family member or an acquaintance, physical and mental health problems, and fear of one's local community being discriminated against as a COVID-19 area were related to anxiety and depression. CONCLUSION: The present study identified COVID-19-related factors associated with anxiety and depression among adolescents, and provides insights regarding potential interventions to improve the mental health of adolescents. To promote the mental health of adolescents during the COVID-19 pandemic, special attention should be paid to individuals with physical or mental-health problems, and efforts should be made to reduce the negative social and emotional impacts of infection-control measures.

Clinical Characteristics of 40 Patients Infected With the SARS-CoV-2 Omicron Variant in Korea.

Since severe acute respiratory syndrome-coronavirus-2 variant B.1.1.529 (omicron) was first reported to the World Health Organization on November 24, 2021, the cases of the omicron variant have been detected in more than 90 countries over the last month. We investigated the clinical and epidemiological characteristics of the first 40 patients with the omicron variant who had been isolated at the National Medical Center in South Korea during December 4-17, 2021. The median age of the patients was 39.5 years. Twenty-two patients (55%) were women. Seventeen patients (42.5%) were fully vaccinated, and none were reinfected with the omicron. Eighteen (45%) had recent international travel history. Half of the patients (19, 47.5%) were asymptomatic, while the others had mild symptoms. Six patients (15%) showed lung infiltrations on chest image; however, none required supplemental oxygen. These mild clinical features are consistent with recent case reports on the omicron variant from other countries.

Booster BNT162b2 COVID-19 Vaccination Increases Neutralizing Antibody Titers Against the SARS-CoV-2 Omicron Variant in Both Young and Elderly Adults.

Concerns about the effectiveness of current vaccines against the rapidly spreading severe acute respiratory syndrome-coronavirus-2 omicron (B.1.1.529) variant are increasing. This study aimed to assess neutralizing antibody activity against the wild-type (BetaCoV/Korea/KCDC03/2020), delta, and omicron variants after full primary and booster vaccinations with BNT162b2. A plaque reduction neutralization test was employed to determine 50% neutralizing dilution (ND50) titers in serum samples. ND50 titers against the omicron variant (median [interquartile range], 5.3 [< 5.0-12.7]) after full primary vaccination were lower than those against the wild-type (144.8 [44.7-294.0]) and delta (24.3 [14.3-81.1]) variants. Furthermore, 19/30 participants (63.3%) displayed lower ND50 titers than the detection threshold (< 10.0) against omicron after full primary vaccination. However, the booster vaccine significantly increased ND50 titers against BetaCoV/Korea/KCDC03/2020, delta, and omicron, although titers against omicron remained lower than those against the other variants (P < 0.001). Our study suggests that booster vaccination with BNT162b2 significantly increases humoral immunity against the omicron variant.

Patient and hospital characteristics predict prolonged emergency department length of stay and in-hospital mortality: a nationwide analysis in Korea.

BACKGROUND: Prolonged emergency department length of stay (EDLOS) in critically ill patients leads to increased mortality. This nationwide study investigated patient and hospital characteristics associated with prolonged EDLOS and in-hospital mortality in adult patients admitted from the emergency department (ED) to the intensive care unit (ICU). METHODS: We conducted a retrospective cohort study using data from the National Emergency Department Information System. Prolonged EDLOS was defined as an EDLOS of ≥ 6 h. We constructed multivariate logistic regression models of patient and hospital variables as predictors of prolonged EDLOS and in-hospital mortality. RESULTS: Between 2016 and 2019, 657,622 adult patients were admitted to the ICU from the ED, representing 2.4% of all ED presentations. The median EDLOS of the overall study population was 3.3 h (interquartile range, 1.9-6.1 h) and 25.3% of patients had a prolonged EDLOS. Patient characteristics associated with prolonged EDLOS included night-time ED presentation and Charlson comorbidity index (CCI) score of 1 or higher. Hospital characteristics associated with prolonged EDLOS included a greater number of staffed beds and a higher ED level. Prolonged EDLOS was associated with in-hospital mortality after adjustment for selected confounders (adjusted odds ratio: 1.18, 95% confidence interval: 1.16-1.20). Patient characteristics associated with in-hospital mortality included age ≥ 65 years, transferred-in, artificially ventilated in the ED, assignment of initial triage to more urgency, and CCI score of 1 or higher. Hospital characteristics associated with in-hospital mortality included a lesser number of staffed beds and a lower ED level. CONCLUSIONS: In this nationwide study, 25.3% of adult patients admitted to the ICU from the ED had a prolonged EDLOS, which in turn was significantly associated with an increased in-hospital mortality risk. Hospital characteristics, including the number of staffed beds and the ED level, were associated with prolonged EDLOS and in-hospital mortality.

Environmental and Genetic Risk Factors of Congenital Anomalies: an Umbrella Review of Systematic Reviews and Meta-Analyses.

BACKGROUND: The prevalence of congenital anomalies in newborns in South Korea was 272.9 per 100,000 in 2005, and 314.7 per 100,000 in 2006. In other studies, the prevalence of congenital anomalies in South Korea was equivalent to 286.9 per 10,000 livebirths in 2006, while it was estimated 446.3 per 10,000 births during the period from 2008 to 2014. Several systematic reviews and meta-analyses analyzing the factors contributing to congenital anomalies have been reported, but comprehensive umbrella reviews are lacking. METHODS: We searched PubMed, Google Scholar, Cochrane, and EMBASE databases up to July 1, 2019, for systematic reviews and meta-analyses that investigated the effects of environmental and genetic factors on any type of congenital anomalies. We categorized 8 subgroups of congenital anomalies classified according to the 10th revision of the International Statistical Classification of Diseases (ICD-10). Two researchers independently searched the literature, retrieved the data, and evaluated the quality of each study. RESULTS: We reviewed 66 systematic reviews and meta-analyses that investigated the association between non-genetic or genetic risk factors and congenital anomalies. Overall, 269 associations and 128 associations were considered for environmental and genetic risk factors, respectively. Congenital anomalies based on congenital heart diseases, cleft lip and palate, and others were associated with environmental risk factors based on maternal exposure to environmental exposures (air pollution, toxic chemicals), parental smoking, maternal history (infectious diseases during pregnancy, pregestational and gestational diabetes mellitus, and gestational diabetes mellitus), maternal obesity, maternal drug intake, pregnancy through artificial reproductive technologies, and socioeconomic factors. The association of maternal alcohol or coffee consumption with congenital anomalies was not significant, and maternal folic acid supplementation had a preventive effect on congenital heart defects. Genes or genetic loci associated with congenital anomalies included MTHFR, MTRR and MTR, GATA4, NKX2-5, SRD5A2, CFTR, and 1p22 and 20q12 anomalies. CONCLUSION: This study provides a wide perspective on the distribution of environmental and genetic risk factors of congenital anomalies, thus suggesting future studies and providing health policy implications.

Prenatal exposure to traffic-related air pollution and risk of congenital diseases in South Korea.

BACKGROUND: Previous studies have suggested links between exposure to ambient air pollutants and increased risk of congenital heart defects. However, few studies have investigated the association between other congenital diseases and traffic-related air pollution. In this study, we assessed the relationship between prenatal exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) with congenital diseases in South Korea. METHODS: Patients with one or more congenital diseases and a control group of patients with non-infective gastroenteritis and colitis with a case:control ratio of 1:3 were obtained from the National Health Insurance Service data for 2008-2013 in South Korea. We estimated the associations of PM2.5 and NO2 exposures with congenital diseases using generalized estimation equations after controlling for covariates. RESULTS: Maternal PM2.5 exposure during the first and second trimester showed positive associations with overall congenital diseases, with changes of 14.7% (95% confidence intervals (CI), 9.3%, 20.3%) and 16.2% (95% CI, 11.0%, 21.7%), respectively, per 11.1 µg/m3 and 10.2 µg/m3 increase of PM2.5 interquartile range (IQR). Similarly, NO2 exposure during the first and second trimester was associated with increased numbers of overall congenital anomalies, with 8.2% (95% CI, 4.2%, 12.3%) and 15.6% (95% CI, 9.3%, 22.2%) more cases, respectively, per 10.6 ppb increase of NO2. We found that maternal PM2.5 exposure during the first and second trimesters of pregnancy was significantly associated with increased risk of specific congenital diseases, including subtypes affecting the circulatory, genitourinary, and musculoskeletal system. However, no significant associations were observed during the third trimester. Maternal NO2 exposure across the entire pregnancy was associated with malformations of the musculoskeletal system. CONCLUSIONS: Our study identified significant links between in utero exposure to PM2.5 and NO2 and certain congenital diseases, and suggests that stricter controls on PM2.5 and NO2 concentrations are required.

The relationship of urinary 3-phenoxybenzoic acid concentrations in utero and during childhood with adiposity in 4-year-old children.

BACKGROUND: Pyrethroid pesticides are reported to be the most commonly used residential insecticides worldwide. We aimed to investigate the relationship between prenatal and postnatal 3-phenoxybenzoic acid (3-PBA) concentrations, and growth and adiposity parameters in 4-year-old children. METHOD: We obtained data from 578 children who participated in the prospective Environment and Development of Children (EDC) study at around 4 years of age (45-55 months) between August 2008 and July 2011. Anthropometric measurements were obtained at age 4 years. Prenatal and postnatal urinary 3-PBA concentration was measured in maternal urine samples at around 20 weeks of gestation, and in the 4-year-old children, respectively. RESULT: The detection frequency of urinary 3-PBA (geometric mean concentration) was 98-99% (0.98 µg/g Cr) in maternal urine, and almost 99-100% (1.34 µg/g Cr) in 4-year-old children. Prenatal urinary3-PBA concentration was not associated with height, weight, or body mass index (BMI) z-scores at 4 years of age, regardless of sex. Postnatal urinary3-PBA concentration was not related to height z-scores, but was positively associated with weight z-scores with marginal significance among only girls (p = 0.058). Analyzed by sex, there was a significant relationship between postnatal urinary 3-PBA concentration and BMI z-scores (p = 0.015) among girls, after adjusting for covariates. CONCLUSION: Childhood urinary 3-PBA concentration measured at 4 years of age was positively associated with BMI z-scores in 4-year-old girls, but prenatal urinary 3-PBA concentration at midterm pregnancy exhibited no association.

Estimation of heat-related deaths during heat wave episodes in South Korea (2006-2017).

In 2016, South Korea experienced extremely high temperatures and the Korea Centre for Disease Control and Prevention (KCDC) reported 17 heat-caused deaths during these heat waves, most due to heat stroke. Because the reported number of heat-caused deaths is only part of the total deaths associated with heat waves, we aimed to estimate attributable deaths during heat wave episodes. We linked mortality to meteorological data in 16 regions in South Korea and estimated relative risk at or above threshold of maximum temperature during summer using generalized linear regression models after controlling for confounders. We computed overall, age-, sex-, and cause-specific attributable deaths from 2006 to 2017. With a 1.5% increase in all-cause mortality per 1 °C increase in concurrent days' maximum temperature during summer, this study estimates a total of 1440 all-cause deaths associated with heat waves during the 2006-2017 study period in South Korea. We estimate that 343 deaths in 2016 can be ascribed to heat waves, which is approximately 20 times more than the number reported by the KCDC (17 heat-caused deaths). This study addresses attributable heat wave deaths in South Korea and illustrates that the reports of medically classified heat-caused deaths seriously underestimate the number of deaths attributable to heat waves. Our findings may enable the implementation and reinforcement of government- and individual-level management strategies for heat waves.

Risk Factors for Severe and Critical Coronavirus Disease 2019 in Children.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is generally mild in children; however, severe or critical cases may occur. In this nationwide study, we analyzed clinical manifestations in children diagnosed with severe acute respiratory syndrome coronavirus 2 to identify high-risk groups for severe or critical disease and compared the clinical features between the Delta- and Omicron-dominant periods. METHODS: Data were retrieved from the National Health Insurance Service (NHIS) database and merged with the Korea Disease Control and Prevention Agency-COVID-19-NHIS cohort, which includes information on COVID-19 cases and vaccination records. We included individuals <20 years old diagnosed with COVID-19 during both periods (Delta: July 25, 2021-January 15, 2022; Omicron: January 16, 2022-March 31, 2022). RESULTS: Proportion of severe or critical cases was higher during the Delta period than during the Omicron period. The Omicron period saw increased hospitalization for pneumonia and croup and increased likelihood of hospitalization for neurological manifestations. The risk of severe COVID-19 depended on age group (Delta: highest for 12-19 years; Omicron: 0-4 years). This risk was high in children with multiple complex chronic conditions during both periods and with obesity or asthma during the Delta but not during the Omicron period. Two-dose COVID-19 vaccination provided strong protection against severe disease in the Delta period (adjusted odds ratio: 0.20), with reduced effectiveness in the Omicron period (adjusted odds ratio: 0.91). However, it significantly reduced the risk of critical illness (adjusted odds ratio: 0.14). CONCLUSIONS: These findings can facilitate identification of children at high risk of severe or critical COVID-19, who may require intensive medical support, and development of vaccination policies.

Risk factors for critical COVID-19 illness during Delta- and Omicron-predominant period in Korea; using K-COV-N cohort in the National health insurance service.

BACKGROUND: This study evaluated the clinical characteristics of patients with COVID-19 in Korea, and examined the relationship between severe COVID-19 cases and underlying health conditions during the Delta (September 20, 2021 to December 4, 2021) and the Omicron (February 20, 2022 to March 31, 2022) predominant period. METHODS: This study assessed the association between critical COVID-19 illness and various risk factors, including a variety of underlying health conditions, using multiple logistic regression models based on the K-COV-N cohort, a nationwide data of confirmed COVID-19 cases linked with COVID-19 vaccination status and the National Health Insurance claim information. RESULTS: We analyzed 137,532 and 8,294,249 cases of COVID-19 infection during the Delta and the Omicron variant dominant periods, respectively. During the Delta as well as the Omicron period, old age (≥80 years) showed the largest effect size among risk factors for critical COVID-19 illness (aOR = 18.08; 95% confidence interval [CI] = 14.71-22.23 for the Delta; aOR = 24.07; 95% CI = 19.03-30.44 for the Omicron period). We found that patients with solid organ transplant (SOT) recipients, unvaccinated, and interstitial lung disease had more than a two-fold increased risk of critical COVID-19 outcomes between the Delta and Omicron periods. However, risk factors such as urban residence, underweight, and underlying medical conditions, including chronic cardiac diseases, immunodeficiency, and mental disorders, had different effects on the development of critical COVID-19 illness between the Delta and Omicron periods. CONCLUSION: We found that the severity of COVID-19 infection was much higher for the Delta variant than for the Omicron. Although the Delta and the Omicron variant shared many risk factors for critical illness, several risk factors were found to have different effects on the development of critical COVID-19 illness between those two variants. Close monitoring of a wide range of risk factors for critical illness is warranted as new variants continue to emerge during the pandemic.

Correction: Risk factors for critical COVID-19 illness during Delta- and Omicron-predominant period in Korea; using K-COV-N cohort in the National health insurance service.

[This corrects the article DOI: 10.1371/journal.pone.0300306.].