Long-term ozone exposure and mortality in patients with chronic kidney disease: a large cohort study.

BACKGROUND: Epidemiologic studies on the effects of long-term exposure to ozone (O3) have shown inconclusive results. It is unclear whether to O3 has an effect on chronic kidney disease (CKD). We investigated the effects of O3 on mortality and renal outcome in CKD. METHODS: We included 61,073 participants and applied Cox proportional hazards models to examine the effects of ozone on the risk of end-stage renal disease (ESRD) and mortality in a two-pollutants model adjusted for socioeconomic status. We calculated the concentration of ozone exposure one year before enrollment and used inverse distance weighting (IDW) for interpolation, where the exposure was evenly distributed. RESULTS: In the single pollutant model, O3 was significantly associated with an increased risk of ESRD and all-cause mortality. Based on the O3 concentration from IDW interpolation, this moving O3 average was significantly associated with an increased risk of ESRD and all-cause mortality. In a two-pollutants model, even after we adjusted for other measured pollutants, nitrogen dioxide did not attenuate the result for O3. The hazard ratio (HR) value for the district-level assessment is 1.025 with a 95% confidence interval (CI) of 1.014-1.035, while for the point-level assessment, the HR value is 1.04 with a 95% CI of 1.035-1.045. The impact of ozone on ESRD, hazard ratio (HR) values are, 1.049(95%CI: 1.044-1.054) at the district unit and 1.04 (95%CI: 1.031-1.05) at the individual address of the exposure assessment. The ozone hazard ratio for all-cause mortality was 1.012 (95% confidence interval: 1.008-1.017) for administrative districts and 1.04 (95% confidence interval: 1.031-1.05) for individual addresses. CONCLUSIONS: This study suggests that long-term ambient O3 increases the risk of ESRD and mortality in CKD. The strategy to decrease O3 emissions will substantially benefit health and the environment.

Blood Pb levels are associated with prostate cancer prevalence among general adult males: Linking National Cancer Registry (2002-2017) and KNHANES (2008-2017) databases of Korea.

BACKGROUND: Exposure to heavy metals may increase the risk of developing prostate cancer. However, these observations are often inconsistent and not based on clinically diagnosed cases. OBJECTIVE: To investigate the association of lead (Pb), cadmium (Cd), and mercury (Hg) exposure with clinically determined prostate cancer cases among adult males in South Korea. METHODS: Metal biomonitoring data and cancer information from the general Korean population were extracted by linking National Cancer Center (NCC) cancer registration data (2002-2017) with Korea National Health and Nutrition Examination Survey (KNHANES) data (2008-2017). Among them, 46 prostate cancer cases (designated as 'all-prostate'), including 25 diagnosed after heavy metal measurement (designated as 'post-prostate'), and 93 matching controls were chosen. Logistic regression analysis was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) between the heavy metal levels and prostate cancer. RESULTS: Post-prostate patients exhibited higher blood Pb levels than controls (median 3.1 µg/dL vs. 2.38 µg/dL, p = 0.01). For all-prostate cancer, the OR of prostate cancer increased by 2.04-fold for every doubling of Pb levels (95% CI = 1.08-3.87, p = 0.03). The OR was also significantly elevated when comparing the third quartile (Q3) to the lowest quartile (Q1), with ORs ranging from 3.38 to 7.95, depending on model (p < 0.05). Blood Pb levels maintained a positive association with inconsistent significance for post-prostate cancer patients. For Cd and Hg, no statistically significant association was established. SIGNIFICANCE: By linking two national health databases for the first time, we constructed an unbiased database of prostate cancer cases and matching controls. We found that blood Pb concentrations were associated with the risk of prostate cancer in Korean men at the current level of exposure.

Association between environmental cadmium exposure and increased mortality in the U.S. National Health and Nutrition Examination Survey (1999-2018).

BACKGROUND: Cadmium (Cd) is toxic to human health and increases overall mortality. In this study, we investigated the association between Cd exposure and all-cause, cardiovascular (CVD), and cancer mortality in the general population and the mediating effect of smoking on these association. METHODS: We used data from U.S. National Health and Nutrition Examination Survey for 1999-2018. To evaluate the hazard ratio (HR) for mortality, a multiple Cox regression analysis was conducted by adjusting for age, sex, race/ethnicity, body mass index, smoking, alcohol, hypertension, diabetes, hyperlipidemia, and history of CVD and cancer. A causal mediation analysis was performed to estimate the effects of smoking. RESULTS: Among the 31,637 subjects, 5452 (12.3%) died. Blood Cd concentrations were significantly associated with all-cause (HR 1.473, 95% confidence interval [CI] 1.403-1.546, p < 0.001), CVD (HR 1.445, 95% CI 1.344-1.554, p < 0.001), and cancer (HR 1.496, 95% CI 1.406-1.592, p < 0.001) mortality. Urinary Cd concentrations were also significantly associated with them. Using feature selection via machine learning, the importance of Cd in all-cause and cancer mortality was second only to age. The association between Cd concentrations and all-cause mortality was significant in both ever-smokers and never-smokers. The mediating effect of smoking was estimated at 32%, whereas a large proportion (68%) remained a direct effect of Cd. In a subgroup analysis of subjects with cancer history, blood Cd concentrations were significantly associated with cancer-related deaths in those with a history of breast, gastrointestinal, and skin cancers. CONCLUSION: High Cd exposure is an important risk factor for all-cause, CVD, and cancer mortality among the general population. Cd exposure increased the risk of death even in never-smokers, and its effects unrelated to smoking were substantial, suggesting the importance of regulating other sources of Cd exposure such as food and water. IMPACT STATEMENT: Using national large-scale data, we found that low-level environmental exposure to cadmium significantly increased the risk of all-cause, cardiovascular, and cancer mortality in the general population even after adjusting for several risk factors. Although smoking is a major source of cadmium exposure, cadmium was nevertheless significantly associated with all-cause mortality in never-smokers, and the mediating effect of smoking on this association was only 32%. Hence, other sources of cadmium exposure such as food and water may be important.

Association of long-term exposure to air pollution with chronic sleep deprivation in South Korea: A community-level longitudinal study, 2008-2018.

BACKGROUND AND OBJECTIVE: Although there are many findings about the effects of fine particulate matter (PM2.5) and sleep deprivation on health respectively, the association between PM2.5 and chronic sleep deprivation has rarely been investigated. Thus, we aimed to investigate this association using a nationwide survey in South Korea. METHOD: We examined the association between long-term exposure to PM2.5 and chronic sleep deprivation using a national cross-sectional health survey covering the entire 226 districts in inland South Korea from 2008 to 2018, with a machine learning-based national air pollution prediction model with 1 km2 spatial resolution. RESULTS: Chronic sleep deprivation was positively associated with PM2.5 in the total population (odds ratio (OR): 1.09, 95% confidence interval (CI): 1.05-1.13) and sub-population (low, middle, high population density areas with OR: 1.127, 1.09, and 1.059, respectively). The association was consistently observed in both sexes (males with OR: 1.09, females with OR: 1.09)) and was more pronounced in the elderly population (OR: 1.12) than in the middle-aged (OR: 1.07) and young (OR: 1.09) populations. CONCLUSIONS: Our results are consistent with the hypothesis regarding the relationship between long-term PM2.5 exposure and chronic sleep deprivation, and the study provides quantitative evidence for public health interventions to improve air quality that can affect chronic sleep conditions.

Excess mortality and the COVID-19 pandemic: causes of death and social inequalities.

BACKGROUND: During the coronavirus diseases 2019 (COVID-19) pandemic, population's mortality has been affected not only by the risk of infection itself, but also through deferred care for other causes and changes in lifestyle. This study aims to investigate excess mortality by cause of death and socio-demographic context during the COVID-19 pandemic in South Korea.  METHODS: Mortality data within the period 2015-2020 were obtained from Statistics Korea, and deaths from COVID-19 were excluded. We estimated 2020 daily excess deaths for all causes, the eight leading causes of death, and according to individual characteristics, using a two-stage interrupted time series design accounting for temporal trends and variations in other risk factors. RESULTS: During the pandemic period (February 18 to December 31, 2020), an estimated 663 (95% empirical confidence interval [eCI]: -2356-3584) excess deaths occurred in South Korea. Mortality related to respiratory diseases decreased by 4371 (3452-5480), whereas deaths due to metabolic diseases and ill-defined causes increased by 808 (456-1080) and 2756 (2021-3378), respectively. The increase in all-cause deaths was prominent in those aged 65-79 years (941, 88-1795), with an elementary school education or below (1757, 371-3030), or who were single (785, 384-1174), while a decrease in deaths was pronounced in those with a college-level or higher educational attainment (1471, 589-2328). CONCLUSION: No evidence of a substantial increase in all-cause mortality was found during the 2020 pandemic period in South Korea, as a result of a large decrease in deaths related to respiratory diseases that offset increased mortality from metabolic disease and diseases of ill-defined cause. The COVID-19 pandemic has disproportionately affected those of lower socioeconomic status and has exacerbated inequalities in mortality.

Ambient carbon monoxide correlates with mortality risk of hemodialysis patients: comparing results of control selection in the case-crossover designs.

BACKGROUND: Growing evidence suggests that environmental air pollution adversely affects kidney health. To date, the association between carbon monoxide (CO) and mortality in patients with end-stage renal disease (ESRD) has not been examined. METHODS: Among 134,478 dialysis patients in the Korean ESRD cohort between 2001 and 2014, 8,130 deceased hemodialysis patients were enrolled, and data were analyzed using bidirectional, unidirectional, and time-stratified case-crossover design. We examined the association between short-term CO concentration and mortality in patients with ESRD. We used a two-pollutant model, adjusted for temperature as a climate factor and for nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and particulate matter less than 10 µm in diameter as air pollution variables other than CO. RESULTS: Characteristics of the study population included age (66.2 ± 12.1 years), sex (male, 59.1%; female, 40.9%), and comorbidities (diabetes, 55.6%; hypertension, 14.4%). Concentration of CO was significantly associated with all-cause mortality in the three case-crossover designs using the two-pollutant model adjusted for SO2. Patients with diabetes or age older than 75 years had a higher risk of mortality than patients without diabetes or those younger than 75 years. CONCLUSION: Findings presented here suggest that higher CO concentration is correlated with increased all-cause mortality in hemodialysis patients, especially in older high-risk patients.

Short-term Exposure to Air Pollution and Attributable Risk of Kidney Diseases: A Nationwide Time-series Study.

BACKGROUND: Several studies have shown that long-term exposure to air pollution is associated with reduced kidney function. However, less is known about effects of short-term exposure to air pollution on kidney disease aggravation and resultant emergency room (ER) burden. This study aimed to estimate excess ER visits attributable to short-term air pollution and to provide evidence relevant to air pollution standards to protect kidney patients. METHODS: We conducted time-series analysis using National Health Insurance data covering all persons in South Korea (2003-2013). We collected daily data for air pollutants (particulate matter ≤10 µm [PM10], ozone [O3], carbon monoxide [CO], and sulfur dioxide [SO2]) and ER visits for total kidney and urinary system disease, acute kidney injury (AKI), and chronic kidney disease (CKD). We performed a two-stage time-series analysis to estimate excess ER visits attributable to air pollution by first calculating estimates for each of 16 regions, and then generating an overall estimate. RESULTS: For all kidney and urinary disease (902,043 cases), excess ER visits attributable to air pollution existed for all pollutants studied. For AKI (76,330 cases), we estimated the highest impact on excess ER visits from O3, while for CKD (210,929 cases), the impacts of CO and SO2 were the highest. The associations between air pollution and kidney ER visits existed for days with air pollution concentrations below current World Health Organization guidelines. CONCLUSION: This study provides quantitative estimates of ER burdens attributable to air pollution. Results are consistent with the hypothesis that stricter air quality standards benefit kidney patients.

Evaluation of the Prognosis of COVID-19 Patients According to the Presence of Underlying Diseases and Drug Treatment.

Certain underlying diseases such as diabetic mellitus and hypertension are a risk factor for the severity and mortality of coronavirus disease (COVID-19) patients. Furthermore, both angiotensin converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARBs) are controversial at role in the process of COVID-19 cases. The aim of the study was to investigate whether underlying diseases and taking ACEi/ARBs, affect the duration of hospitalization and mortality in patients with confirmed COVID-19. Medical usage claims data for the past three years until 15 May 2020, from the "CORONA-19 International Cooperation Research" project was used. We analyzed the medical insurance claims data for all 7590 coronavirus (COVID-19) patients confirmed by RT-PCR tests nationwide up to 15 May 2020. Among the comorbidities, a history of hypertension (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.056-2.158) and diabetes (HR, 1.867; 95% CI, 1.408-2.475) were associated significantly with mortality. Furthermore, heart failure (HR, 1.391; 95% CI, 1.027-1.884), chronic obstructive pulmonary disease (HR, 1.615; 95% CI, 1.185-2.202), chronic kidney disease (HR, 1.451; 95% CI, 1.018-2.069), mental disorder (HR, 1.61; 95% CI, 1.106-2.343), end stage renal disease (HR, 5.353; 95% CI, 2.185-13.12) were also associated significantly with mortality. The underlying disease has increased the risk of mortality in patients with COVID-19. Diabetes, hypertension, cancer, chronic kidney disease, heart failure, and mental disorders increased mortality. Controversial whether taking ACEi/ARBs would benefit COVID-19 patients, in our study, patients taking ACEi/ARBs had a higher risk of mortality.

Effects of residential greenness on clinical outcomes of patients with chronic kidney disease: a large-scale observation study.

BACKGROUND: As industrialization and urbanization are accelerating, the distribution of green areas is decreasing, particularly in developing countries. Since the 2000s, the effects of surrounding greenness on self-perceived health, including physical and mental health, longevity, and obesity have been reported. However, the effects of surrounding green space on chronic kidney disease are not well understood. Therefore, we investigated the impact of residential greenness on the mortality of chronic kidney disease patients and progression from chronic kidney disease to end-stage renal disease (ESRD). METHODS: Using a large-scale observational study, we recruited chronic kidney disease patients (n = 64,565; mean age, 54.0 years; 49.0% of male) who visited three Korean medical centers between January 2001 and December 2016. We investigated the hazard ratios of clinical outcomes per 0.1-point increment of exposure to greenness using various models. RESULTS: During the mean follow-up of 6.8 ± 4.6 years, 5,512 chronic kidney disease patients developed ESRD (8.5%) and 8,543 died (13.2%). In addition, a 0.1-point increase in greenness reduced all-cause mortality risk in chronic kidney disease and ESRD patients and progression of chronic kidney disease to ESRD in a fully adjusted model. The association between mortality in ESRD patients and the normalized difference vegetation index was negatively correlated in people aged >65 years, who had normal weight, were nonsmokers, and lived in a nonmetropolitan area. CONCLUSION: Chronic kidney disease patients who live in areas with higher levels of greenness are at reduced risk of all-cause mortality and progression to ESRD.

Effects of air pollution on mortality of patients with chronic kidney disease: A large observational cohort study.

Due to industrialization, the burden of diseases associated with air pollution is increasing. Although the risk associated with air pollution in the general population has been actively investigated, few studies have been conducted on the effects of exposure to air pollution in patients with chronic kidney disease (CKD) in East Asia. A total of 29,602 patients with CKD in Seoul participated in a retrospective cohort at three medical centers. We assessed the association of individualized exposure to five types of air pollutants (PM2.5, PM10, NO2, SO2, and CO) using inverse distance weighting (IDW) on mortality in CKD patients in the Cox proportional hazard model that was adjusted for sex, age, eGFR, hemoglobin, hypertension, diabetes, and area-level characteristics. During the 6.14 ± 3.96 years, 3863 deaths (13%) were observed. We confirmed the significant effects of PM2.5 (hazard ratio [HR] 1.17, 95% confidence interval [CI] 1.07-0.29) and CO (HR 1.17, 95% CI 1.00-1.38) on mortality in CKD patients. Different associations were found when stratified by age, body mass index, smoking, and drinking status. Long-term exposure to air pollutants had negative effects on mortality in patients with CKD. These effects were prominent in patients aged over 65 years, patients with a lean body, and those who did not drink alcohol.

Clinical outcomes associated with long-term exposure to airborne particulate pollution in kidney transplant recipients.

BACKGROUND: Researchers have yet to investigate the specific association between 10-µm particulate matter (PM10) levels and the risk of graft failure, kidney disease, or the functional decline of transplanted kidneys, in kidney transplant recipients (KTRs). Furthermore, we know very little about the association between PM10 levels and the development of allograft rejection in transplanted kidneys. Identification of air pollution as a potential contributor to kidney disease could help reduce future disease burden, stimulate policy discussions on the importance of reducing air pollution with respect to health and disease, and increase public awareness of the hazards of air pollution. We aimed to evaluate the relationship of PM10 with the risk of graft failure, mortality, and decline of graft function in KTRs. METHODS: Air pollutant data were obtained from the Korean National Institute of Environmental Research. We then investigated potential associations between these data and the clinical outcomes of 1532 KTRs who underwent kidney transplantation in a tertiary hospital between 2001 and 2015. Survival models were used to evaluate the association between PM10 concentrations and the risk of death-censored graft failure (DCGF), all-cause mortality, and biopsy-proven rejection (BPR), over a median follow-up period of 6.31 years. RESULTS: The annual mean PM10 exposure after kidney transplantation was 27.1 ± 8.0 µg/m3. Based on 1-year baseline exposure, 1 µg/m3 increase in PM10 concentration was associated with an increased risk of DCGF (hazard ratio (HR): 1.049; 95% confidence interval (CI): 1.014-1.084) and BPR (HR: 1.053; 95% CI: 1.042-1.063). Fully adjusted models showed that all-cause mortality was significantly associated with 1-year average PM10 concentrations (HR, 1.09; 95% CI, 1.043 to 1.140). CONCLUSIONS: Long-term PM10 exposure is significantly associated with BPR, DCGF, and all-cause mortality in KTRs.

Post-farmgate food value chains make up most of consumer food expenditures globally.

Progress towards many United Nations Sustainable Development Goals depends on interventions in food value chains, yet data and methods have thus far limited the production of cross-nationally comparable estimates of food value chains' magnitudes. Here we develop a standardized method and data series to estimate the distribution of consumer food expenditures between value-added activities on farms and in the post-farmgate value chain. Using data from 61 countries over 2005-2015, representing 90% of the global economy, we show that farmers receive, on average, 27% of consumer expenditure on foods consumed at home and a far lower percentage of food consumed away from home. That figure consistently falls in the 16-38% range for middle- and high-income countries and falls significantly as incomes rise. The large and growing post-farmgate food value chain merits greater attention as the world grapples with the economic, environmental and social impacts of food systems.

Long-Term Effects of Air Pollutants on Mortality Risk in Patients with End-Stage Renal Disease.

Long-term exposure to air pollutants significantly increases the morbidity and mortality associated with various diseases. However, little is known about the relationship between air pollutants and end-stage renal disease (ESRD)-related mortality. A total of 5041 patients who started dialysis between 2008 and 2015 were prospectively enrolled in the Clinical Research Center for End-Stage Renal Disease (CRC-ESRD) cohort study. We assigned a daily mean concentration of air pollutants (PM10, NO2, and SO2) to each participant. Time-varying Cox models were used to investigate the relationship between air pollutants and mortality in ESRD patients. During the follow-up period (mean 4.18 years), 1475 deaths occurred among 5041 participants. We found a significant long-term relationship between mortality risk and PM10 (HR 1.33, CI 1.13-1.58), NO2 (HR 1.46, CI 1.10-1.95), and SO2 (HR 1.07, CI 1.03-1.11). Elderly patients and patients who lived in metropolitan areas had an increased risk associated with PM10. Elderly patients also had increased risks associated NO2 and SO2. Long-term exposure to air pollutants had negative effects on mortality in ESRD patients. These effects were prominent in elderly patients who lived in metropolitan areas, suggesting that ambient air pollution, in addition to traditional risk factors, is important for the survival of these patients.

Short-term PM2.5 exposure and emergency hospital admissions for mental disease.

Epidemiologic studies regarding the relationship between short-term exposure to particulate matter with a median aerodynamic diameter < 2.5 µm (PM2.5) and mental disease are limited. This study examined the effects of short-term exposure to PM2.5 on emergency admissions to the hospital for mental disease in Seoul, Korea. Data regarding 80,634 emergency admissions for mental diseases were collected from a nationally centralized healthcare claims database in Seoul during 2003-2013. Generalized linear models with climate variables were used to examine associations between short-term PM2.5 exposure and mental disease admissions. To comprehensively assess PM2.5 effects, we used single- and two-pollutant models, which considered other pollutants in combination with PM2.5. The relative risk (RR) of emergency admissions for mental disease was 1.008 (95% confidence interval, 1.001-1.015) for each 10 µg/m3 increase in 2-day average PM2.5 concentration. This effect persisted or became slightly stronger in the two-pollutant models that included carbon monoxide, nitrogen dioxide, ozone, or sulfur dioxide (RR, 1.01-1.021), but association appeared to be limited to individuals < 65 years of age. Significant association was estimated only during the warm season (RR, 1.021-1.023) in the two-pollutant models. The exposure-response curve was steeper at lower concentrations, suggesting that the risk of mental disease at lower concentrations of pm2.5 (0-30 µg/m3). PM2.5 was associated with increased admissions even when it was below the World Health Organization's Air Quality Guidelines (25 µg/m3), but the association was not statistically significant. Thus, based on the data from a large database, exposure to PM2.5 was associated with increases in emergency admissions for mental diseases, and this association was significant during the warm season. PM2.5 may even affect mental disease at levels below the current air quality guidelines. These results provide substantial insight regarding the effects of air pollutants and have important implications for policy makers.

Association between extreme temperature and kidney disease in South Korea, 2003-2013: Stratified by sex and age groups.

Weather conditions due to climate change affect the health directly and indirectly. Previous studies have shown associations with temperature, heat wave, and cold spell, and these do not only result in mortality from cardiovascular disease, respiratory disease, etc., but also in morbidity. This study aimed to quantify the relative risk for hospital admissions related to ambient temperature for genitourinary system diseases, which are representative of metabolic disease. We conducted a nationwide retrospective cohort study using claims data generated by medical services for diseases of the urinary system. The data was based on medical claims data from 16 districts in South Korea, to the nationwide level between 2003 and 2013. A total of 1,255,671 hospital admissions through the emergency department because of diseases of the genitourinary system were reported within the study period. The overall cumulative relative risk at the 99th percentile vs. the minimum morbidity percentile for renal diseases was 1.252 (95% confidence interval 1.211 to 1.294) in Seoul, 1.252 (1.21 to 1.296) in Busan, 1.236 (1.196 to 1.276) in Daegu, 1.237(1.197 to 1.279) in Gwangju, and 1.258 (1.218 to 1.299) in Gyeonggi-do, 1.278 (1.211 to 1.349) in Chungcheongbuk-do, 1.291 (1.235 to 1.35) in Gyeongsangnam-do. In the group of men over 65 years, the overall cumulative RR was high and statistically significant in acute kidney injury (AKI). But we could not find the effect of high temperature for chronic kidney disease (CKD). The association were rather opposite, but not statistically significant. Our nationwide study not only demonstrates relative risk considering lag effects associated with ambient temperature and trends in hospital admissions through the emergency department for genitourinary disorders but also observed differences among disease groups.

Projection of Future Mortality Due to Temperature and Population Changes under Representative Concentration Pathways and Shared Socioeconomic Pathways.

The Paris Agreement aims to limit the global temperature increase to below 2 °C above pre-industrial levels and to pursue efforts to limit the increase to even below 1.5 °C. Now, it should be asked what benefits are in pursuing these two targets. In this study, we assessed the temperature⁻mortality relationship using a distributed lag non-linear model in seven major cities of South Korea. Then, we projected future temperature-attributable mortality under different Representative Concentration Pathway (RCP) and Shared Socioeconomic Pathway (SSP) scenarios for those cities. Mortality was projected to increase by 1.53 under the RCP 4.5 (temperature increase by 2.83 °C) and 3.3 under the RCP 8.5 (temperature increase by 5.10 °C) until the 2090s, as compared to baseline (1991⁻2015) mortality. However, future mortality is expected to increase by less than 1.13 and 1.26 if the 1.5 °C and 2 °C increase targets are met, respectively, under the RCP 4.5. Achieving the more ambitious target of 1.5 °C will reduce mortality by 12%, when compared to the 2 °C target. When we estimated future mortality due to both temperature and population changes, the future mortality was found to be increased by 2.07 and 3.85 for the 1.5 °C and 2 °C temperature increases, respectively, under the RCP 4.5. These increases can be attributed to a growing proportion of elderly population, who is more vulnerable to high temperatures. Meeting the target of 1.5 °C will be particularly beneficial for rapidly aging societies, including South Korea.

Effect modification of individual- and regional-scale characteristics on heat wave-related mortality rates between 2009 and 2012 in Seoul, South Korea.

Many studies have investigated the associations between heat waves, ambient temperature, cold spells, and mortality or morbidity. Some studies have utilized effect modification to reveal the factors that increase an individual's susceptibility to temperature extremes, which can then be used to reshape public policy. In this study, we used a time-stratified case-crossover technique to examine how individual- and regional-scale characteristics modified heat wave-related impacts on mortality rates in Seoul, South Korea, between 2009 and 2012. We defined a heat wave as having at least two consecutive days with a daily mean temperature greater than or equal to the 95th percentile recorded in each of Seoul's twenty-five districts. At the individual scale, citizens classified as belonging to a lower education group had a higher vulnerability to heat wave-related morbidity or mortality [odds ratio (OR) 1.261; 95% confidence interval (CI): 1.034-1.538]. At a regional scale, death during heat waves was more likely to occur in districts with a high deprivation index (OR=1.194; 95% CI: 1.028-1.388). And a low proportion of green space around buildings (OR=1.178; 95% CI: 1.016-1.366), a low proportion of rooftop green space (OR=1.207; 95% CI: 1.042-1.399), or those that had fewer hospitals (OR=1.186; 95% CI: 1.019-1.379). Our data show that mortality during heat waves is more likely where these individual and regional-scale vulnerabilities overlap. Our findings support evidence of mortality impacts from heat waves and provide a basis for selection to policy makers choose on the target groups to reduce the public health burden of heat waves.