Pathogen-specific response of infectious gastroenteritis to ambient temperature: National surveillance data in the Republic of Korea, 2015-2019.

OBJECTIVE: The objective of this study was to investigate the relationship between ambient temperature and common viral and bacterial gastroenteritis in the Republic of Korea, which has a high-income and temperate climate, considering the different lagged effects of each causative pathogen. METHODS: We obtained the number of weekly reported cases of infectious gastroenteritis caused by norovirus, group A rotavirus, enteric adenovirus, Clostridium perfringens, non-typhoidal Salmonella, and Campylobacter between 2015 and 2019 from the Korean Infectious Diseases Sentinel Surveillance System. We obtained weather data from the Korea Meteorological Administration for the same period. Generalized linear models with quasi-Poisson distributions and distributed lag non-linear models were utilized after adjusting for relative humidity, precipitation, long-term trends, and seasonality. We investigated the associations between weekly mean temperature and the weekly number of reported cases of each type of infectious gastroenteritis by applying different maximum lags for each type. RESULTS: Compared with the 50th percentile temperature, the lag-cumulative relative risks (RRs) with 95% confidence intervals (CIs) at the 5th percentile temperature for norovirus gastroenteritis, rotavirus gastroenteritis, adenovirus gastroenteritis were 11.0 (4.7-25.7), 2.7 (1.4-5.2), and 4.7 (1.4-15.8) by applying the maximum lag of 6, 4, and 3 weeks, respectively. Compared with the 50th percentile temperature, the lag-cumulative RRs with 95% CIs at the 95th percentile temperature for C. perfringens gastroenteritis, Salmonella gastroenteritis, and Campylobacter gastroenteritis were 1.2 (0.8-1.9), 3.0 (1.5-6.2), and 2.0 (1.1-3.6), by applying the maximum lag of 2, 3, and 2 weeks, respectively. CONCLUSIONS: Cold temperature increased the risk of viral gastroenteritis and showed relatively long lagged effects. Hot temperature increased the risk of bacterial gastroenteritis and showed relatively short lagged effects.

Population Response to Air Pollution and the Risk of Coronavirus Disease in Chinese Cities during the Early Pandemic Period.

Health behavior is a critical measure in controlling the coronavirus disease 2019 (COVID-19) pandemic. We estimated the effect of health behaviors against air pollution on reducing the risk of COVID-19 during the initial phase of the pandemic. The attack rates of COVID-19 in 159 mainland Chinese cities during the first 2 weeks after the closure of major cities was estimated; air pollution level as a surrogate indicator of the mask-wearing rate. Data on air pollution levels and meteorologic factors 2 weeks prior to the closure were obtained. The attack rate was compared with the level of air pollution using a generalized linear model after adjusting for confounders. When fine particulates (PM2.5) and nitrogen dioxide (NO2) levels increased by one unit of air quality index (AQI), the infection risk decreased by 0.7% and 3.4%, respectively. When PM2.5 levels exceeded 150 (level 4), the infection risk decreased (relative risk, RR = 0.635, 95% confidence interval, CI: 0.442 to 0.912 for level 4; RR = 0.529, 95% CI: 0.337 to 0.830 for level 5; respectively). After controlling for the number of high-speed railway routes, when PM2.5 and NO2 levels increased by one AQI, relative risk for PM2.5 and NO2 was 0.990 (95% CI, 0.984 to 0.997) and 0.946 (95% CI, 0.911 to 0.982), respectively, demonstrating a consistently negative association. It is postulated that, during the early phase of the pandemic, the cities with higher air pollution levels may represent the higher practice of mask-wearing to protect from air pollution, which could have acted as a barrier to the transmission of the virus. This study highlights the importance of health behaviors, including mask-wearing for preventing infections.

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.

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.

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.

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

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.

Effects of El Niño/La Niña on the Number of Imported Shigellosis Cases in the Republic of Korea, 2004-2017.

Shigellosis is a major diarrheal disease in low- and middle-income countries. Although the incidence of such diseases in South and Southeast Asia has been associated with climate fluctuations linked to the El Niño-Southern Oscillation (ENSO), the impact of ENSO on shigellosis infections remains unknown. Data reported to being infected with shigellosis while traveling abroad from 2004 to 2017 were obtained from the Korea Centers for Disease Control and Prevention. We investigated the relationship between the Oceanic Niño Index (ONI) and Indian Ocean Dipole Mode Index and the relative risk of shigellosis in outbound travelers using distributed lag linear and non-linear models. From 2004 to 2017, 87.1% of imported shigellosis was infected in South and Southeast Asian countries. The relative risk of imported shigellosis infection in outbound travelers increased as the ONI decreased. In the association with the five-month cumulative ONI, the relative risk of infection continuously increased as the La Niña index gained strength. Climate fluctuations associated with the La Niña phenomenon in South and Southeast Asian countries can lead to issues in sanitation and water safety. Our findings suggest that the decreasing trend in the ONI is associated with an increased incidence of shigellosis in these countries.

Associations between the Risk of Internet Addiction and Problem Behaviors among Korean Adolescents.

BACKGROUND: The number of internet users is increasing rapidly and internet addiction among adolescents has become a serious public health problem in Korea. In the light of behavioral addiction, this study was aimed to identify the associations between the risk of internet addiction and other problem behaviors which can lead to addiction, such as cigarette smoking, alcohol drinking, drug abuse, and sexual intercourse among a nationally representative sample of Korean adolescents. METHODS: Data from the 2010 Korean Youth Risk Behavior Web-based Survey (respondents, 73,238) were analyzed. Risk of internet addiction was assessed by the 'Korean Internet Addiction Proneness Scale for Youth-Short Form: Self Report' which was developed by the Korean National Information Society Agency in 2008. Multiple logistic regression analysis was used to calculate the odds ratios of problem behaviors among adolescents at high risk for internet addiction and adolescents at low risk for internet addiction. RESULTS: The odds of smoking experience, drug abuse experience, and sexual intercourse experience were significantly higher among boys at high risk for internet addiction compared to boys at low risk for internet addiction. Among girls at high risk of internet addiction, the odds of smoking experience, drinking experience, and drug abuse experience were significantly higher compared with girls at low risk of internet addiction. CONCLUSION: The risk of internet addiction was associated with cigarette smoking, alcohol drinking, drug abuse, and sexual intercourse experience among Korean adolescents.