Universal health coverage saves more lives among severely ill COVID-19 patients: A difference-in-differences analysis of individual patient data in South Korea.

BACKGROUND: Universal health coverage (UHC) ensures affordability of a variety of essential health services for the general population. Although UHC could mitigate the harmful effects of coronavirus disease 2019 (COVID-19) on patients and their socioeconomic position, the debate on UHC's scope and ability to improve health outcomes is ongoing. This study aimed to identify the impact of UHC policy withdrawal on the health outcomes of South Korea's severely ill COVID-19 patients. METHODS: We used a propensity score matching (PSM) and difference-in-differences combined model. This study's subjects were 44,552 hospitalized COVID-19 patients contributing towards health insurance claims data, COVID-19 notifications and vaccination data extracted from the National Health Information Database and the Korea Disease Control and Prevention Agency from 1 December 2020 to 30 April 2022. After PSM, 2460 patients were included. This study's exposures were severity of illness and UHC policy change. The primary outcome was the case fatality rate (CFR) for COVID-19, which was defined as death within 30 days of a COVID-19 diagnosis. There were four secondary outcomes, including time interval between diagnosis and hospitalization (days), length of stay (days), total medical expenses (USD) and the time interval between diagnosis and death (days). RESULTS: After the UHC policy's withdrawal, the severely ill patients' CFR increased to 284 per 1000 patients [95% confidence interval (CI) 229.1-338.4], hospitalization days decreased to 9.61 days (95% CI -11.20 to -8.03) and total medical expenses decreased to 5702.73 USD (95% CI -7128.41 to -4202.01) compared with those who were not severely ill. CONCLUSIONS: During the pandemic, UHC may have saved the lives of severely ill COVID-19 patients; therefore, expanding services and financial coverage could be a crucial strategy during public health crises.

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.

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.].

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.

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.

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.

Women's Employment in Industries and Risk of Preeclampsia and Gestational Diabetes: A National Population Study of Republic of Korea.

Background: Some working conditions may pose a higher physical or psychological demand to pregnant women leading to increased risks of pregnancy complications. Objectives: We assessed the association of woman's employment status and the industrial classification with obstetric complications. Methods: We conducted a national population study using the National Health Information Service database of Republic of Korea. Our analysis encompassed 1,316,310 women who experienced first-order live births in 2010-2019. We collected data on the employment status and the industrial classification of women, as well as their diagnoses of preeclampsia (PE) and gestational diabetes mellitus (GDM) classified as A1 (well controlled by diet) or A2 (requiring medication). We calculated odds ratios (aORs) of complications per employment, and each industrial classification was adjusted for individual risk factors. Results: Most (64.7%) were in employment during pregnancy. Manufacturing (16.4%) and the health and social (16.2%) work represented the most prevalent industries. The health and social work exhibited a higher risk of PE (aOR = 1.11, 95% confidence interval [CI]: 1.03-1.21), while the manufacturing industry demonstrated a higher risk of class A2 GDM (1.20, 95% CI: 1.03-1.41) than financial intermediation. When analyzing both classes of GDM, women who worked in public administration and defense/social security showed higher risk of class A1 GDM (1.04, 95% CI: 1.01, 1.07). When comparing high-risk industries with nonemployment, the health and social work showed a comparable risk of PE (1.02, 95% CI: 0.97, 1.07). Conclusion: Employment was associated with overall lower risks of obstetric complications. Health and social service work can counteract the healthy worker effect in relation to PE. This highlights the importance of further elucidating specific occupational risk factors within the high-risk industries.

Does the father's job matter? Parental occupation and preterm birth in Korea.

OBJECTIVES: Limited evidence is available regarding the impact of paternal occupation and its combined effect with maternal occupation on preterm birth. Therefore, we assessed the association of maternal and paternal occupations with preterm birth. METHODS: We used the national birth data of Korea between 2010 and 2020. Parental occupations were divided into 5 categories: (1) managers; (2) professionals, technicians, and related workers; (3) clerks and support workers; (4) service and sales workers; and (5) manual workers. A multinomial logistic regression model was used to calculate the adjusted odds ratios (aORs) of extremely, very, and moderate-to-late preterm births per occupational category considering individual risk factors. RESULTS: For the 4,004,976 singleton births, 40.2% of mothers and 95.5% of fathers were employed. Compared to non-employment, employment was associated with a lower risk of preterm birth. Among employed mothers, service and sales occupations were associated with a higher risk of preterm birth than managerial occupations (aOR, 1.06; 95% confidence interval [CI], 1.01 to 1.10 for moderate-to-late preterm births). The father's manual occupation was associated with a higher risk of preterm birth (aOR, 1.09; 95% CI, 1.05 to 1.13 for moderate-to-late preterm) than managerial occupations. When both parents had high-risk occupations, the risk of preterm birth was higher than in cases where only the mother or neither of the parents had a high-risk occupation. CONCLUSIONS: Paternal occupation was associated with preterm birth regardless of maternal employment and occupation and modified the effect of maternal occupation. Detailed occupational environment data are needed to identify the paternal exposures that increase the risk.

Did the socioeconomic inequalities in avoidable and unavoidable mortality worsen during the first year of the COVID-19 pandemic in Korea?

OBJECTIVES: This study examined changes in socioeconomic inequalities in mortality in Korea before and after the outbreak of coronavirus disease 2019 (COVID-19). METHODS: From 2017 to 2020, age-standardized mortality rates were calculated for all-cause deaths, avoidable deaths (preventable deaths, treatable deaths), and unavoidable deaths using National Health Insurance claims data and Statistics Korea's cause of death data. In addition, the slope index of inequality (SII) and the relative index of inequality (RII) by six income levels (Medical Aid beneficiary group and quintile of health insurance premiums) were computed to analyze the magnitude and change of mortality inequalities. RESULTS: All-cause and avoidable mortality rates decreased steadily between 2017 and 2020, whereas unavoidable mortality remained relatively stable. In the case of mortality inequalities, the disparity in all-cause mortality between income classes was exacerbated in 2020 compared to 2019, with the SII increasing from 185.44 to 189.22 and the RII increasing from 3.99 to 4.29. In particular, the preventable and unavoidable mortality rates showed an apparent increase in inequality, as both the SII (preventable: 91.31 to 92.01, unavoidable: 69.99 to 75.38) and RII (preventable: 3.42 to 3.66, unavoidable: 5.02 to 5.89) increased. CONCLUSIONS: In the first year of the COVID-19 pandemic, mortality inequality continued to increase, although there was no sign of exacerbation. It is necessary to continuously evaluate mortality inequalities, particularly for preventable and unavoidable deaths.

Unequal burdens of COVID-19 infection: a nationwide cohort study of COVID-19-related health inequalities in Korea.

OBJECTIVES: While the Korean government's response to the coronavirus disease 2019 (COVID-19) pandemic is considered effective given the relatively low mortality rate, issues of inequality have been insufficiently addressed. This study explored COVID-19-related health inequalities in Korea. METHODS: Age standardization for various health inequality indices was derived using data from the Korean National Health Insurance Service, the Korea Disease Control and Prevention Agency, and the Microdata Integrated Service of Statistics Korea. The slope index of inequality (SII) and relative index of inequality (RII) were calculated for socioeconomic variables, while absolute difference (AD) and relative difference (RD) were used for gender and disability inequalities. RESULTS: We observed a number of COVID-19-related health outcome inequalities. Gender inequality was particularly noticeable in infection rates, with the rate of women 1.16 times higher than that of men. In contrast, socioeconomic inequality was evident in vaccination rates, with a 4.5-fold (SII, -4.519; 95% confidence interval, -7.403 to -1.634) difference between the highest and lowest household income groups. Regarding clinical progression post-infection, consistent findings indicated higher risk for men (RD for hospitalization, 0.90; severe cases, 0.54; and fatality, 0.65), individuals with disabilities (RD for hospitalization, 2.27; severe cases, 2.29; and fatality, 2.37), and those from lower socioeconomic groups (SII for hospitalization, 1.778; severe cases, 0.089; and fatality, 0.451). CONCLUSIONS: While the infection risk was nearly ubiquitous, not everyone faced the same level of risk post-infection. To prevent further health inequalities, it is crucial to develop a thoughtful policy acknowledging individual health conditions and resources.

Trend of Women's Health Research in Korea, 2012-2020: Topic and Text Network Analysis.

BACKGROUND: With the epidemiological transition, sociodemographic changes and differential lifetime experiences of women, women's health research improves knowledge of diverse health issues and the impact of policies. To explore the initiatives of women's health research in Korea, the present study examined the trends and topics of research on women's health funded by the government. METHODS: We searched all research projects on women's health funded by the government between 2012 and 2020 in Korea using the National Science & Technology Information Service database. We reviewed all the titles and abstract of the projects and examined the research trends by year. Content analysis was performed using both deductive and inductive approaches. Text network analysis and visualization by topic were conducted for keywords with a minimum of 10 occurrences in the title and abstract. RESULTS: Total number and funding amount of research projects on women's health in 2020 increased by 2.4 and 2.2 times over 2012 levels, respectively. The Ministry of Health and Welfare and the Ministry of Food and Drug Safety funded 20.9% of all projects. The majority of the topics (59.8%) addressed breast and gynecological cancers. Those on sexual and reproductive health accounted for 16.7%, with steep growth in the number (6.1 times) and funding (11.1 times) over 2012 levels. The topic analysis presented a more complex keyword network in 2020 than in 2012; however, the keywords frequently used in 2020 were similar to those of 2012. CONCLUSION: Women's health research projects have been growing in number and funding, with limited diversity in topics. Diversifying the topics and focusing on issues beyond the breast and pregnancy would be needed to reflect the complete life course of women. Institutionalization of diverse communication channels with various interest groups for women's health would be needed to better understand women's health needs from a public health perspective.

Risk of adverse pregnancy outcomes by maternal occupational status: A national population-based study in South Korea.

OBJECTIVE: This study examined the association between maternal occupational status and adverse pregnancy outcomes in the general South Korean population. METHODS: We analyzed 1 825 845 employed and non-employed women with a diagnostic code for pregnancy in the National Health Insurance Service (NHIS) database (2010-2019) of South Korea. Based on their employment status and type of occupation, we calculated risk ratios for three adverse outcomes: early abortive outcomes (miscarriage, ectopic pregnancy, and molar pregnancy), stillbirth, and no live birth (diagnosis of pregnancy with no record of live birth thereafter, which include early abortive outcomes and stillbirth) with adjusting for covariates. RESULTS: Overall, 18.0%, 0.7%, and 39.8% ended in early abortive outcomes, stillbirths, and no live births, respectively. The risk of early abortive outcomes and stillbirths was higher in non-employed women than in employed women, while no live births were more frequent in employed women. Those in the health and social work industry showed the highest risk of no live births. Manufacturing jobs (1.030, 95% CI: 1.013, 1.047) and health/social work (1.029, 95% CI: 1.012, 1.046) were associated with an increased risk of early abortive outcomes compared with financial and insurance jobs. Consistently higher risks of no live births were observed in the manufacturing, wholesale/retail trade, education, health/social work, and public/social/personal service occupation. CONCLUSION: Employment during pregnancy and several occupation types were associated with a higher risk of pregnancy loss. Additional research using detailed job activity data is needed to determine specific occupational causes of adverse pregnancy outcomes.

Age-specific influences of refractive error and illuminance on pupil diameter.

To assess the most influential factor for pupil diameter changes among age, illuminance, and refractive state and reestablish the optimal procedures for clinical applications based on refractive state and illuminance for different age groups. The study was an observational study (repeated measure study). Participants included 219 Korean adults aged 20 to 69 years. Pupil diameters were measured using a pupilometer under scotopic, mesopic-low, and mesopic-high lighting conditions. Factor interactions among age, illuminance, and refractive state were evaluated using mixed linear model and chi-square automated interaction detection. Illuminance mainly contributed to variations in pupil diameter of participants over 50 years, whereas the refractive state was the dominant controlling factor for the pupil variation in participants below 50 years. For more generalized application, the pupil diameter decreased with older age and brighter illuminance (P < .001, inverse correlation, all comparisons). The mean pupil diameter was significantly higher in myopes and emmetropes than in hyperopes (P < .001). Pupil diameter variation modeled using the mixed model confirmed age, illuminance, and refractive error as significant factors (P < .001). Accounting for the interactions among age, illuminance, and refractive error and establishing their hierarchical dominance can be generalized using the chi-square automated interaction detection method and mixed model. Promoting age-dependent consideration for both illuminance and refractive state is necessary when pupil diameters play significant roles in clinical and manufacturing circumstances.

Pregnancy loss and Income in the Republic of Korea using National Health Insurance Service Data, 2008-2014.

BACKGROUND: Although unintentional pregnancy loss is common, national representative statistics are lacking in high-income East Asian countries undergoing rapid demographic changes. It is necessary to confirm the income inequality of pregnancy loss even in universal national health insurance. METHOD: Using National Health Insurance Service data between 2008 and 2014, the annual prevalence of pregnancy loss was enumerated, and differences in pregnancy loss according to age and income levels were assessed by multivariable Poisson regression. Joint-point regression was used to examine the trend of pregnancy loss. RESULT: On average, there was a 15.0% annual pregnancy loss among 3,941,020 pregnancy cases from 2008 to 2014. Pregnancy loss inequality increased stepwise with income levels except for the highest income group. After adjusting for income levels, the annual percent change of age-standardized prevalence significantly increased by 2.6% every year since 2011. CONCLUSION: Even in high-income countries with universal national health insurance, income inequality in pregnancy loss is observed. Further appraisal is needed to explain the increasing trend of pregnancy loss between 2011 and 2014 even after adjusting income.

Contracting Out National Immunization Program Does Not Improve Vaccination Rate Nor Socioeconomic Inequality: A Case Study of Seasonal Influenza Vaccination in South Korea.

The objective of the present study was to investigate if the policy for contracting out the Korean influenza National Immunization Program (NIP) for individuals aged ≥ 65 years affects a reduction in vaccination inequality based on gender and socioeconomic position (SEP). In South Korea, initially only public health centers provided influenza vaccination for free; however, starting from the fall of 2015, the program was expanded to include private medical institutions. The policy was expected to improve overall vaccination rate and reduce its inequality, through improving access to vaccination. The present study analyzed how the gap in the vaccination rate changed between before and after contracting out. A multivariate logistic regression model stratified by gender and SEP of individuals aged ≥ 65 years was used. The study also analyzed changes in the unvaccinated rates between before and after contracting out based on an interrupted time series model. The gap in the unvaccinated rate based on SEP present prior to contracting out of the NIP for individuals aged ≥ 65 years did not decrease afterwards. In particular, the step changes were 0.94% (95% confidence interval [CI]: 0.00, 1.89) and 1.34% (95% CI: 1.17, 1.52) in men and women, respectively. In the pre-policy period, among women, the unvaccinated rate of the medical aid beneficiaries group was 1.22-fold higher (95% CI: 1.12, 1.32) than that of the health insurance beneficiaries, and the difference was not reduced post-policy implementation (odds ratio: 1.27, 95% CI: 1.20, 1.36). The findings of the study were that contracting out of the NIP was not effective in improving vaccination rate nor resolving vaccination inequality. Future studies should focus on identifying the mechanism of vaccination inequality and exploring measures for resolving such inequality.

Variability in daily or weekly working hours and self-reported mental health problems in Korea, Korean working condition survey, 2017.

BACKGROUND: Working hour regulation in Korea is being revised to allow increasing variability in number of working hours. We sought to investigate the association between variability in the number of daily or weekly working hours with or without long working hours (> 52 h/w) and mental health among South Korean workers. METHODS: We used data from 28,345 full-time, non-shift employed workers working more than 30 h per week participating in the Korean Working Condition Survey in 2017. We defined six groups according to variability in daily or weekly working hours (same number vs different number) and weekly working hours (31-40, 41-52, > 52 h per week). Odds ratios (ORs) and confidence intervals (CIs) for self-reported depressive symptoms and anxiety were calculated using workers with same number of working hours/31-40 h per week as the reference. RESULTS: Variability in number of work hours every day or week combined with > 52 working hours per week showed the highest risk of depressive symptoms (OR = 5.13, 95% CI 3.25-8.11) and anxiety (OR = 3.75, 95% CI 2.39-5.88) compared to the reference group, controlling for age, sex, education, occupation, industry, salary, workers' choice of working hours and overtime payment. Workers working ≤52 h/w were adversely impacted by variable working hours as well. CONCLUSIONS: Variable daily or weekly working hours were associated with poorer self-reported depressive and anxiety symptoms in Korea, among full-time and non-shift workers. Reform of the Korean Labor Standards Act warrants consideration.

Mainstreaming of Health Equity in Infectious Disease Control Policy During the COVID-19 Pandemic Era.

The Korean government's strategy to combat coronavirus disease 2019 (COVID-19) has focused on non-pharmaceutical interventions, such as social distancing and wearing masks, along with testing, tracing, and treatment; overall, its performance has been relatively good compared to that of many other countries heavily affected by COVID-19. However, little attention has been paid to health equity in measures to control the COVID-19 pandemic. The study aimed to examine the unequal impacts of COVID-19 across socioeconomic groups and to suggest potential solutions to tackle these inequalities. The pathways linking social determinants and health could be entry points to tackle the unequal consequences of this public health emergency. It is crucial for infectious disease policy to consider social determinants of health including poor housing, precarious working conditions, disrupted healthcare services, and suspension of social services. Moreover, the high levels of uncertainty and complexity inherent in this public health emergency, as well as the health and socioeconomic inequalities caused by the pandemic, underscore the need for good governance other than top-down measures by the government. We emphasize that a people-centered perspective is a key approach during the pandemic era. Mutual trust between the state and civil society, strong accountability of the government, and civic participation are essential components of cooperative disaster governance.

Increased risk of suicide after occupational injury in Korea.

OBJECTIVES: This study sought to investigate the association between occupational injury and subsequent risk of suicide in Korea. METHODS: We linked compensation data for 775 537 workers injured at work during 2003-2014 with National Death Registry through 2015. Suicide among injured workers was compared with the economically active population in Korea separately for men and women by calculating SMRs, with 95% CIs. RESULTS: Injured workers showed higher mortality from suicide for both men (SMR=2.22, 95% CI 2.14 to 2.31) and women (SMR=2.11, 95% CI 1.81 to 2.45) compared with the economically active population in Korea. CONCLUSIONS: Occupational injuries are associated with substantially elevated suicide risk in Korea. The results suggest the importance of social policies to protect and support injured workers as well as intensifying efforts to prevent workplace injuries.

Recalibration and validation of the Charlson Comorbidity Index in an Asian population: the National Health Insurance Service-National Sample Cohort study.

Weights assigned to comorbidities in predicting mortality may vary based on the type of index disease and advances in the management of comorbidities. We aimed to develop a modified version of the Charlson Comorbidity Index (CCI) using an Asian nationwide database (mCCI-A), enabling the precise prediction of mortality rates in this population. The main data source used in this study was the National Health Insurance Service-National Sample Cohort (NHIS-NSC) obtained from the National Health Insurance database, which includes health insurance claims filed between January 1, 2002, and December 31, 2013, in Korea. Of the 1,025,340 individuals included in the NHIS-NSC, 570,716 patients who were hospitalized at least once were analyzed in this study. In total, 399,502 patients, accounting for 70% of the cohort, were assigned to the development cohort, and the remaining patients (n = 171,214) were assigned to the validation cohort. The mCCI-A scores were calculated by summing the weights assigned to individual comorbidities according to their relative prognostic significance determined by a multivariate Cox proportional hazard model. The modified index was validated in the same cohort. The Cox proportional hazard model provided reassigned severity weights for 17 comorbidities that significantly predicted mortality. Both the CCI and mCCI-A were correlated with mortality. However, compared with the CCI, the mCCI-A showed modest but significant increases in the c statistics. According to the analyses using continuous net reclassification improvement, the mCCI-A improved the net mortality risk reclassification by 44.0% (95% confidence intervals (CI), 41.6-46.5; p < 0.001). The mCCI-A facilitates better risk stratification of mortality rates in Korean inpatients than the CCI, suggesting that the mCCI-A may be a preferable index for use in clinical practice and statistical analyses in epidemiological studies.

Estimation of the number of working population at high-risk of COVID-19 infection in Korea.

OBJECTIVES: We aimed to identify occupational groups at high-risk of coronavirus disease 2019 (COVID-19) infection in Korea, to estimate the number of such workers, and to examine the prevalence of protective resources by employment status. METHODS: Based on the sixth Standard Occupational Classification codes, 2015 census data were linked with data from the fifth Korean Working Conditions Survey, which measured how frequently workers directly come into contact with people other than fellow employees in the workplace. RESULTS: A total of 30 occupational groups, including 7 occupations from the healthcare and welfare sectors and 23 from other sectors, were classified as high-risk occupational groups involving frequent contact with people other than fellow employees in the workplace (more than half of the working hours). Approximately 1.4 million (women, 79.1%) and 10.7 million workers (46.3%) are employed in high-risk occupations. Occupations with a larger proportion of women are more likely to be at a high-risk of infection and are paid less. For wage-earners in high-risk occupations, protective resources to deal with COVID-19 (e.g., trade unions and health and safety committees) are less prevalent among temporary or daily workers than among those with permanent employment. CONCLUSIONS: Given the large number of Koreans employed in high-risk occupations and inequalities within the working population, the workplace needs to be the key locus for governmental actions to control COVID-19, and special consideration for vulnerable workers is warranted.