Establishment of the Korea National Health and Nutrition Examination Survey air pollution study dataset for the researchers on the health impact of ambient air pollution / 한국역학회지

To provide a nationwide representative dataset for the study on health impact of air pollution, we combined the data from the Korea National Health and Nutrition Examination Survey with the daily air quality and weather data by matching the date of examination and the residential address of the participants. The database of meteorological factors and air quality as sources of exposure data were estimated using the Community Multiscale Air Quality model. The linkage dataset was merged by three ways; administrative district, si-gun-gu (city, county, and district), and geocode (in latitude and longitude coordinate units) based on the participants’ residential address, respectively. During the study period, the exposure dataset of 85,018 individuals (38,306 men and 46,712 women) whose examination dates were recorded were obtained. According to the definition of exposure period, the dataset was combined with the data on short-term, mid-term, and long-term exposure to air pollutants and the meteorological indices. Calculation of the daily merged dataset’s average air pollution linked by si-gun-gu and geocode units showed similar results. This study generated a daily average of meteorological indices and air pollution exposure dataset for all regions including rural and remote areas in Korea for 11 years. It is expected to provide a platform for the researchers studying the health impact of air pollution and climate change on the representative population and area, which may facilitate the establishment of local health care plans by understanding the residents’ health status at the local as well as national level.

Establishment of the Korea National Health and Nutrition Examination Survey air pollution study dataset for the researchers on the health impact of ambient air pollution / 한국역학회지

To provide a nationwide representative dataset for the study on health impact of air pollution, we combined the data from the Korea National Health and Nutrition Examination Survey with the daily air quality and weather data by matching the date of examination and the residential address of the participants. The database of meteorological factors and air quality as sources of exposure data were estimated using the Community Multiscale Air Quality model. The linkage dataset was merged by three ways; administrative district, si-gun-gu (city, county, and district), and geocode (in latitude and longitude coordinate units) based on the participants’ residential address, respectively. During the study period, the exposure dataset of 85,018 individuals (38,306 men and 46,712 women) whose examination dates were recorded were obtained. According to the definition of exposure period, the dataset was combined with the data on short-term, mid-term, and long-term exposure to air pollutants and the meteorological indices. Calculation of the daily merged dataset’s average air pollution linked by si-gun-gu and geocode units showed similar results. This study generated a daily average of meteorological indices and air pollution exposure dataset for all regions including rural and remote areas in Korea for 11 years. It is expected to provide a platform for the researchers studying the health impact of air pollution and climate change on the representative population and area, which may facilitate the establishment of local health care plans by understanding the residents’ health status at the local as well as national level.

Relationship Between Non-alcoholic Fatty Liver Disease and Decreased Bone Mineral Density: A Retrospective Cohort Study in Korea / 예방의학회지

Objectives@#The aim of this retrospective cohort study was to investigate whether non-alcoholic fatty liver disease (NAFLD) was associated with incident bone mineral density (BMD) decrease. @*Methods@#This study included 4536 subjects with normal BMD at baseline. NAFLD was defined as the presence of fatty liver on abdominal ultrasonography without significant alcohol consumption or other causes. Decreased BMD was defined as a diagnosis of osteopenia, osteoporosis, or BMD below the expected range for the patient’s age based on dual-energy X-ray absorptiometry. Cox proportional hazards models were used to estimate the hazard ratio of incident BMD decrease in subjects with or without NAFLD. Subgroup analyses were conducted according to the relevant factors. @*Results@#Across 13 354 person-years of total follow-up, decreased BMD was observed in 606 subjects, corresponding to an incidence of 45.4 cases per 1000 person-years (median follow-up duration, 2.1 years). In the model adjusted for age and sex, the hazard ratio was 0.65 (95% confidence interval, 0.51 to 0.82), and statistical significance disappeared after adjustment for body mass index (BMI) and cardiometabolic factors. In the subgroup analyses, NAFLD was associated with a lower risk of incident BMD decrease in females even after adjustment for confounders. The direction of the effect of NAFLD on the risk of BMD decrease changed depending on BMI category and body fat percentage, although the impact was statistically insignificant. @*Conclusions@#NAFLD had a significant protective effect on BMD in females. However, the effects may vary depending on BMI category or body fat percentage.

Compliance of Antihypertensive Medication and Risk of Coronavirus Disease 2019: a Cohort Study Using Big Data from the Korean National Health Insurance Service

Background@#There is a controversy whether it is safe to continue renin-angiotensin system blockers in patients with coronavirus disease 2019 (COVID-19). We analyzed big data to investigate whether angiotensin-converting enzyme inhibitors and/or angiotensin II receptor blockers have any significant effect on the risk of COVID-19. Population-based cohort study was conducted based on the prescription data from nationwide health insurance records. @*Methods@#We investigated the 1,374,381 residents aged ≥ 40 years living in Daegu, the epicenter of the COVID-19 outbreak, between February and March 2020. Prescriptions of antihypertensive medication during the year before the outbreak were extracted from the National Health Insurance Service registry. Medications were categorized by types and stratified by the medication possession ratios (MPRs) of antihypertensive medications after controlling for the potential confounders. The risk of COVID-19 was estimated using a difference in difference analysis. @*Results@#Females, older individuals, low-income earners, and recently hospitalized patients had a higher risk of infection. Patients with higher MPRs of antihypertensive medications had a consistently lower risk of COVID-19 than those with lower MPRs of antihypertensive medications and non-users. Among patients who showed complete compliance, there was a significantly lower risk of COVID-19 for those prescribed angiotensin II receptor blockers (relative risk [RR], 0.751; 95% confidence interval [CI], 0.587–0.960) or calcium channel blockers (RR, 0.768; 95% CI, 0.601–0.980). @*Conclusion@#Renin-angiotensin system blockers or other antihypertensive medications do not increase the risk of COVID-19. Patients should not stop antihypertensive medications, including renin-angiotensin system blockers, because of concerns of COVID-19.

Trends of accidental carbon monoxide poisoning in Korea, 1951-2018 / 한국역학회지

OBJECTIVES@#Carbon monoxide (CO) poisoning from coal briquette combustion has been a major public health problem in Korea. In this study, we estimated the time trends of the consumption of anthracite coal and the number of CO poisoning victims over the past 7 decades, in the context of changes in heating facilities. @*METHODS@#Using Population and Housing Census data and energy statistics, we estimated the number of houses using briquettes as heating fuel between 1951 and 2018. After estimating the incidence of CO poisoning in housing units by heating facility type, we determined the ratio of the number of household members who experienced CO poisoning to the overall number of household members. Finally, we estimated the distribution of the victims according to poisoning severity, excluding victims of intentional exposure. @*RESULTS@#We estimated that, overall, over 26 million people experienced CO poisoning between 1951 and 2018 in Korea. The household consumption of anthracite peaked in 1986, but the number of victims of CO poisoning peaked at approximately 1 million people in 1980. From 1951 to 2018, the cumulative number of CO poisoning victims comprised approximately 22,830,000 mild cases, 3,570,000 severe cases, and 65,000 deaths. @*CONCLUSIONS@#The peak in the number of CO poisoning victims occurred 6 years earlier than the peak in the number of people using briquettes for heating. This gap resulted from improvements in briquette heating systems. This finding provides a quantitative basis for epidemiological studies on the health outcomes of CO poisoning in the Korean population.

A small window into the status of malaria in North Korea: estimation of imported malaria incidence among visitors from South Korea / 한국역학회지

OBJECTIVES@#This study aimed to develop hypotheses on trends in malaria incidence in North Korea using malaria incidence among South Korean visitors to North Korea. @*METHODS@#The number of South Korean tourists who visited Mount Kumgang from 2000 to 2008 and the number of South Korean employees at the Kaesong Industrial Complex from 2005 to 2015 were obtained from the Korean Statistical Information Service. The number of malaria cases among South Koreans who visited North Korea was obtained from a previous report. The incidence of malaria per 100,000 person-years was calculated using these data and compared with the malaria incidence in North Korea derived from published articles. @*RESULTS@#A high incidence of malaria in 2001 and a sharp decline in the following years were observed in both South and North Korean data. Since then, North Korean data showed a relatively low and stable incidence, but the incidence among South Koreans visiting North Korea increased in 2006. Considering the trends in mass primaquine preventive treatment, floods, and economic growth rate, the incidence of malaria may have increased in North Korea in 2006. Since 2009, the incidence of malaria decreased gradually according to both South and North Korean data. @*CONCLUSIONS@#The trends of malaria incidence in North Korea could be reflected through its incidence among South Koreans who visited North Korea. For future inter-Korean collaboration aiming to eradicate malaria, we propose that a North Korean malaria monitoring system be established applying this method.

Trends of accidental carbon monoxide poisoning in Korea, 1951-2018 / 한국역학회지

OBJECTIVES@#Carbon monoxide (CO) poisoning from coal briquette combustion has been a major public health problem in Korea. In this study, we estimated the time trends of the consumption of anthracite coal and the number of CO poisoning victims over the past 7 decades, in the context of changes in heating facilities. @*METHODS@#Using Population and Housing Census data and energy statistics, we estimated the number of houses using briquettes as heating fuel between 1951 and 2018. After estimating the incidence of CO poisoning in housing units by heating facility type, we determined the ratio of the number of household members who experienced CO poisoning to the overall number of household members. Finally, we estimated the distribution of the victims according to poisoning severity, excluding victims of intentional exposure. @*RESULTS@#We estimated that, overall, over 26 million people experienced CO poisoning between 1951 and 2018 in Korea. The household consumption of anthracite peaked in 1986, but the number of victims of CO poisoning peaked at approximately 1 million people in 1980. From 1951 to 2018, the cumulative number of CO poisoning victims comprised approximately 22,830,000 mild cases, 3,570,000 severe cases, and 65,000 deaths. @*CONCLUSIONS@#The peak in the number of CO poisoning victims occurred 6 years earlier than the peak in the number of people using briquettes for heating. This gap resulted from improvements in briquette heating systems. This finding provides a quantitative basis for epidemiological studies on the health outcomes of CO poisoning in the Korean population.

A small window into the status of malaria in North Korea: estimation of imported malaria incidence among visitors from South Korea / 한국역학회지

OBJECTIVES@#This study aimed to develop hypotheses on trends in malaria incidence in North Korea using malaria incidence among South Korean visitors to North Korea. @*METHODS@#The number of South Korean tourists who visited Mount Kumgang from 2000 to 2008 and the number of South Korean employees at the Kaesong Industrial Complex from 2005 to 2015 were obtained from the Korean Statistical Information Service. The number of malaria cases among South Koreans who visited North Korea was obtained from a previous report. The incidence of malaria per 100,000 person-years was calculated using these data and compared with the malaria incidence in North Korea derived from published articles. @*RESULTS@#A high incidence of malaria in 2001 and a sharp decline in the following years were observed in both South and North Korean data. Since then, North Korean data showed a relatively low and stable incidence, but the incidence among South Koreans visiting North Korea increased in 2006. Considering the trends in mass primaquine preventive treatment, floods, and economic growth rate, the incidence of malaria may have increased in North Korea in 2006. Since 2009, the incidence of malaria decreased gradually according to both South and North Korean data. @*CONCLUSIONS@#The trends of malaria incidence in North Korea could be reflected through its incidence among South Koreans who visited North Korea. For future inter-Korean collaboration aiming to eradicate malaria, we propose that a North Korean malaria monitoring system be established applying this method.

Malaria Incidence of the Regions Adjacent to the Demilitarized Zone in the Democratic People's Republic of Korea, 2004–2016

BACKGROUND: Vivax malaria reemerged in the Korean peninsula in 1990s beginning from the western border area and spread across both Koreas rapidly with its peak incidences reported on the early 2000s. There have been few reports on the malaria incidence in the Democratic People's Republic of Korea (North Korea) that provides detailed epidemiological features. The purpose of this study was to describe the time trends and spatial distribution of malaria in North Korea with comparison to those in South Korean regions across the border. METHODS: The incidence of malaria in each province of North Korea from 2004 to 2016 was estimated based on data from domestic and international health authorities. Consistency of the data was evaluated by calculating the ratio of malaria cases in each province to the total cases each year. We also compared the changes in malaria incidence over time in South and North Korea adjacent to the demilitarized zone. RESULTS: In North Korea, the incidence of malaria in the three provinces adjacent to the demilitarized zone was the highest (52.1−315.3 per 100,000), followed by Pyeonganbuk-do (14.7−113.5 per 100,000), where railways and road networks were connected to northern China. The incidence of malaria in each province of North Korea reported after 2011 was more consistent than when compared with previous annual data, and there was also a positive correlation between changes in incidence over time when compared with malaria incidence in South Korea (r = 0.855, r = 0.596). CONCLUSION: The malaria report of North Korea was relatively consistent in its spatiotemporal tendency since 2011, suggesting improvement of the quality of the surveillance data. The strong correlation between North and South Korean malaria incidence at regional level suggests that collaboration between both sides are essential for the successful elimination of malaria in the Korean peninsula.

Health Indicators Related to Disease, Death, and Reproduction / 예방의학회지

One of the primary goals of epidemiology is to quantify various aspects of a population’s health, illness, and death status and the determinants (or risk factors) thereof by calculating health indicators that measure the magnitudes of various conditions. There has been some confusion regarding health indicators, with discrepancies in usage among organizations such as the World Health Organization the, Centers for Disease Control and Prevention (CDC), and the CDC of other countries, and the usage of the relevant terminology may vary across papers. Therefore, in this review, we would like to propose appropriate terminological definitions for health indicators based on the most commonly used meanings and/or the terms used by official agencies, in order to bring clarity to this area of confusion. We have used appropriate examples to make each health indicator easy for the reader to understand. We have included practical exercises for some health indicators to help readers understand the underlying concepts.

Epidemiologic Trends and Seasonality of Scabies in South Korea, 2010–2017

Scabies is a parasitic skin infection with intense itching. Scabies infection seriously impairs quality of life, while outbreaks in medical institutions cause financial losses. This study aimed to present the annual and seasonal trend of prevalence of scabies in the national population. Scabies cases were extracted from National Health Insurance Service database and its epidemiologic characteristics were assessed. To analyze the seasonality of scabies occurrence, temperature and humidity were included in the model as weather factors, and the per capita gross national income index was adjusted. The annual prevalence by age group was 0.56–0.69 per 1,000 persons until the age of 40 years and peaked at 3.0–4.1 per 1,000 persons in the age group over 80 years. The number of women diagnosed with scabies has been consistently higher compared to that of men since 2010. Mean number of cases diagnosed as scabies was lowest in spring, approximately 4,000 cases, when the average temperature was less than 5°C at 2 months prior, whereas more than 6,000 scabies cases occurred in autumn when temperatures exceeded 25°C at 2 months prior. This study presents the epidemiological characteristics and seasonality of all cases nationwide over 8 years and will help to establish control policies.

Health Indicators Related to Disease, Death, and Reproduction / 예방의학회지

One of the primary goals of epidemiology is to quantify various aspects of a population’s health, illness, and death status and the determinants (or risk factors) thereof by calculating health indicators that measure the magnitudes of various conditions. There has been some confusion regarding health indicators, with discrepancies in usage among organizations such as the World Health Organization the, Centers for Disease Control and Prevention (CDC), and the CDC of other countries, and the usage of the relevant terminology may vary across papers. Therefore, in this review, we would like to propose appropriate terminological definitions for health indicators based on the most commonly used meanings and/or the terms used by official agencies, in order to bring clarity to this area of confusion. We have used appropriate examples to make each health indicator easy for the reader to understand. We have included practical exercises for some health indicators to help readers understand the underlying concepts.

Burden of Disease Attributable to Inadequate Drinking Water, Sanitation, and Hygiene in Korea

BACKGROUND: Diarrheal and intestinal infectious disease caused by inadequate drinking water, sanitation, and hygiene (WASH) is not only a great concern in developing countries but also a problem in low-income populations and rural areas in developed countries. In this study, we assessed the exposure to inadequate WASH in Korea and estimated the burden of disease attributable to inadequate WASH. METHODS: We used observational data on water supply, drinking water, sewage treatment rate, and hand washing to assess inadequate WASH conditions in Korea, and estimated the level of exposure in the entire population. The disease burden was estimated by applying the cause of death data from death registry and the morbidity data from the national health insurance to the population attributable fraction (PAF) for the disease caused by inappropriate WASH. RESULTS: In 2013, 1.4% of the population were exposed to inadequate drinking water, and 1.0% were living in areas where sewerage was not connected. The frequency of handwashing with soap after contact with excreta was 23.5%. The PAF due to inadequate WASH as a cluster of risk factors was 0.353 (95% confidence interval [CI], 0.275–0.417), among which over 90% were attributable to hand hygiene factors that were significantly worse than those in American and European high-income countries. CONCLUSION: The level of hand hygiene in Korea has yet to be improved to the extent that it shows a significant difference compared to other high-income countries. Therefore, improving the current situation in Korea requires a continuous hand washing campaign and a program aimed at all people. In addition, continuous policy intervention for improvement of sewage treatment facilities in rural areas is required, and water quality control monitoring should be continuously carried out.

Estimation of Cancer Incidence and Mortality Risks Attributed to Diagnostic Medical Radiation Exposure in Korea, 2013

BACKGROUND: Radiation exposure from medical procedures has been rapidly increasing. We purposed to estimate the fraction of cancer incidence and mortality attributed to diagnostic medical radiation exposure in Korea. METHODS: Using information on diagnostic medical radiation exposure from various sources including national health examination (National Health Insurance Service), private health examination, and conscription health examination; the annual mean exposed organ dose (mGy) from all diagnostic medical radiation use, grouped by sex and 5-year age ranges up to 80 years, was calculated. Cancer incidence and mortality lifetime attributable risks (LARs) up to 85 years using estimated exposed organ doses and biological effects of ionizing radiation (BEIR) VII model (excess relative risk and excess absolute risk) were estimated. Using background cancer incidence and mortality risk based on the national database, along with estimated LARs, we finally estimated population attributable fraction (PAF) of cancer incidence and mortality. RESULTS: The PAF for diagnostic medical radiation exposure among all cancers of Koreans was 0.9% for incidence and mortality, resulting 1,915 cancer cases and 637 cancer deaths a year. The PAF in females was higher than those in males: 1.2% and 1.7% (incidence and mortality) versus 0.6% (same in incidence and mortality), respectively. CONCLUSION: The estimated PAF for diagnostic medical radiation in Korea in 2013 was higher than those reported in the UK in 2004. Optimized management of diagnostic medical radiation use is important in Korea.

Asymptomatic Middle East Respiratory Syndrome coronavirus infection using a serologic survey in Korea / 한국역학회지

OBJECTIVES: The rates of asymptomatic infection with Middle East Respiratory Syndrome (MERS) coronavirus vary. A serologic study was conducted to determine the asymptomatic MERS infection rate in healthcare workers and non-healthcare workers by exposure status. METHODS: Study participants were selected from contacts of MERS patients based on a priority system in 4 regions strongly affected by the 2015 MERS outbreak. A sero-epidemiological survey was performed in 1,610 contacts (average duration from exposure to test, 4.8 months), and the collected sera were tested using an enzyme-linked immunespecific assay (ELISA), immunofluorescence assay (IFA), and plaque reduction neutralization antibody test (PRNT). Among the 1,610 contacts, there were 7 ELISA-positive cases, of which 1 exhibited positive IFA and PRNT results. RESULTS: The asymptomatic infection rate was 0.060% (95% confidence interval, 0.002 to 0.346). The asymptomatic MERS case was a patient who had been hospitalized with patient zero on the same floor of the hospital at the same time. The case was quarantined at home for 2 weeks after discharge, and had underlying diseases, including hypertension, angina, and degenerative arthritis. CONCLUSIONS: The asymptomatic infection was acquired via healthcare-associated transmission. Thus, it is necessary to extend serologic studies to include inpatient contacts who have no symptoms.

Premature Deaths Attributable to Long-term Exposure to Ambient Fine Particulate Matter in the Republic of Korea

BACKGROUND: Ambient fine particulate matter (PM2.5) is the major environmental health risk factor in Korea. Exposure to PM2.5 has been a growing public concern nationwide. With the rapid aging of the Korean population, the health effects attributable to long-term exposure to PM2.5 were expected to increase further in the future. We aimed to estimate premature deaths attributable to long-term exposure to ambient PM(2.5) in Korea. METHODS: A modelled estimation of long-term exposure to PM2.5 was used to calculate the nationwide exposure level. Hazard ratios of long-term exposure to PM2.5 were obtained from a large prospective cohort study in North America. Modified cause of death (CoD) data, which applied the garbage code reclassification algorithm, were used to calculate premature deaths attributable to long-term exposure to PM2.5. RESULTS: From 1990 to 2013, the average population-weighted PM2.5 concentration in Korea was 30.2 μg/m3. The estimated number of premature deaths was 17,203 (95% confidence interval [CI], 11,056–22,772). The most common CoD was ischemic stroke (5,382; 3,101–7,403), followed by cancer of trachea, bronchus, and lung (4,958; 2,857–6,820), hemorrhagic stroke (3,452; 1,989–4,748), and ischemic heart disease (3,432; 1,383–5,358). CONCLUSION: Premature deaths due to long-term exposure to PM2.5 accounted for 6.4% of all deaths in Korea. However, individual efforts alone cannot prevent the effects of air pollution. This disease burden study can serve as a basis for the establishment of government policies and budgets and can be used to assess the effectiveness of environmental health policies.

Estimation of the National Burden of Disease and Vulnerable Population Associated with Natural Disasters in Korea: Heavy Precipitation and Typhoon

BACKGROUND: Despite its growing significance, studies on the burden of disease associated with natural disasters from the perspective of public health were few. This study aimed at estimating the national burden of disease associated with typhoons and torrential rains in Korea. METHODS: During the period of 2002–2012, 11 typhoons and five torrential rains were selected. Mortality and morbidities were defined as accentual death, injury and injury-related infection, and mental health. Their incidences were estimated from National Health Insurance Service. Case-crossover design was used to define the disaster-related excess mortality and morbidity. Disability-adjusted life years (DALYs) were directly assessed from excess mortality and morbidity. RESULTS: The burden of disease from typhoons increased with the intensity, with 107.7, 30.6, and 36.6 DALYs per 100,000 per event for strong, moderate, and weak typhoons, respectively. Burden of disease from torrential rains were 56.9, 52.8, and 26.4 DALYs per 100,000 per event for strong, moderate, and weak episodes, respectively. Mental disorders contributed more years lived with disability (YLDs) than did injuries in most cases, but the injury-induced YLDs associated with strong typhoon and torrential rain were higher than those of lower-intensity. The elderly was the most vulnerable to most types of disaster and storm intensities, and males younger than 65 years were more vulnerable to a strong torrential rain event. CONCLUSION: The intensity of torrential rain or typhoon was the strongest determinant of the burden of disease from natural disasters in Korea. Population vulnerable may vary depending on the nature and strength of the disasters.

Ambient air quality and subjective stress level using Community Health Survey data in Korea / 한국역학회지

OBJECTIVES: Air pollution causes various disease in exposed populations, and can lead to premorbid health effects manifested as both physical and psychological functional impairment. The present study investigated the subjective stress level in daily life in relation to the level of air pollution. METHODS: Data from the Community Health Survey (2013), comprising 99,162 men, and 121,273 women residing in 253 healthcare administrative districts, were combined with air pollutant concentration modelling data from the Korean Air Quality Forecasting System, and were stratified by subjective stress levels into five strata for multiple logistic regression. Levels of exposure were divided into five quintiles according to the annual concentration of nitrogen dioxide (NO2), and were analyzed using a single-pollutant model using NO2 concentration only, and a multi-pollutant model adjusted for the concentration of particulate matter < 10 µm in diameter. RESULTS: Analysis of men and women in various age groups showed the highest odds ratio (OR) for subjective stress level at the highest NO2 concentration quintile in men and women aged 30–64 years (men: 2.91; 95% confidence interval [CI], 2.12 to 4.01; women: 1.82; 95% CI, 1.32 to 2.51). As the NO2 concentration quintile increased, the OR increased. Men showed higher ORs than women in all strata. CONCLUSIONS: In the present study, annual NO2 concentrations were found to be associated with subjective stress levels. This association was especially clear among socioeconomically active men and women aged 30–64 years.

Asymptomatic Middle East Respiratory Syndrome coronavirus infection using a serologic survey in Korea / 한국역학회지

OBJECTIVES@#The rates of asymptomatic infection with Middle East Respiratory Syndrome (MERS) coronavirus vary. A serologic study was conducted to determine the asymptomatic MERS infection rate in healthcare workers and non-healthcare workers by exposure status.@*METHODS@#Study participants were selected from contacts of MERS patients based on a priority system in 4 regions strongly affected by the 2015 MERS outbreak. A sero-epidemiological survey was performed in 1,610 contacts (average duration from exposure to test, 4.8 months), and the collected sera were tested using an enzyme-linked immunespecific assay (ELISA), immunofluorescence assay (IFA), and plaque reduction neutralization antibody test (PRNT). Among the 1,610 contacts, there were 7 ELISA-positive cases, of which 1 exhibited positive IFA and PRNT results.@*RESULTS@#The asymptomatic infection rate was 0.060% (95% confidence interval, 0.002 to 0.346). The asymptomatic MERS case was a patient who had been hospitalized with patient zero on the same floor of the hospital at the same time. The case was quarantined at home for 2 weeks after discharge, and had underlying diseases, including hypertension, angina, and degenerative arthritis.@*CONCLUSIONS@#The asymptomatic infection was acquired via healthcare-associated transmission. Thus, it is necessary to extend serologic studies to include inpatient contacts who have no symptoms.

Ambient air quality and subjective stress level using Community Health Survey data in Korea / 한국역학회지

OBJECTIVES@#Air pollution causes various disease in exposed populations, and can lead to premorbid health effects manifested as both physical and psychological functional impairment. The present study investigated the subjective stress level in daily life in relation to the level of air pollution.@*METHODS@#Data from the Community Health Survey (2013), comprising 99,162 men, and 121,273 women residing in 253 healthcare administrative districts, were combined with air pollutant concentration modelling data from the Korean Air Quality Forecasting System, and were stratified by subjective stress levels into five strata for multiple logistic regression. Levels of exposure were divided into five quintiles according to the annual concentration of nitrogen dioxide (NO2), and were analyzed using a single-pollutant model using NO2 concentration only, and a multi-pollutant model adjusted for the concentration of particulate matter < 10 µm in diameter.@*RESULTS@#Analysis of men and women in various age groups showed the highest odds ratio (OR) for subjective stress level at the highest NO2 concentration quintile in men and women aged 30–64 years (men: 2.91; 95% confidence interval [CI], 2.12 to 4.01; women: 1.82; 95% CI, 1.32 to 2.51). As the NO2 concentration quintile increased, the OR increased. Men showed higher ORs than women in all strata.@*CONCLUSIONS@#In the present study, annual NO2 concentrations were found to be associated with subjective stress levels. This association was especially clear among socioeconomically active men and women aged 30–64 years.