Abstract
Objectives
This study aimed to elucidate climate–health vulnerability in the Chungcheong region (i.e., Daejeon, Sejong, Chungcheongbuk-do, and Chungcheongnam-do) and examine in-depth analytical statistics and evidence for establishing climate–health policies and risk communication strategies at the national and regional levels.
Methods
Data derived from the Heat Injury Surveillance System by the Korea Disease Control and Prevention Agency in 2025 were used to monitor incidents of heat injuries and heat-related illnesses in the Chungcheong region (36 municipalities). Additional analyses were conducted using meteorological and healthcare utilization data from the Korea Meteorological Administration and Health Insurance Review and Assessment Service, respectively. Regional incidence rates were calculated as the number of heat-related illness cases per 100,000 population. To visualize regional distribution, a hexagon binning (hexbin) tool was applied.
Results
In 2025, a total of 527 heat-related illness cases were reported in the Chungcheong region. Men accounted for 426 cases (80.8%), which is approximately four times higher than women (101 cases, 19.2%). The highest proportion of cases was observed for individuals aged 40–59 years (171 cases, 32.4%). The proportion of cases for individuals aged 60 years and older was 39.6%, representing a decrease of 2.2 percentage points compared with the previous year. The study noted substantial regional disparities in heat-related illness cases, ranging from 2.3 per 100,000 population in Dong-gu, Daejeon, to 49.6 per 100,000 population in Okcheon County, Chungcheongbuk-do, which corresponds to a 21.6-fold difference. In Chungcheongnam-do, the areas exhibiting the most number of cases remained consistent with those observed in the previous year, including Cheongyang County (40.9), Yesan County (25.4), and Dangjin City (23.8). In Chungcheongbuk-do, the ranking of high-incidence areas was reversed compared with the previous year, with Okcheon County (49.6), Danyang County (40.6), and Boeun County (36.2) obtaining the highest rates. Estimated heat-related deaths occurred exclusively in Chungcheongnam-do, with two deaths reported in Dangjin and one each in Cheongyang, Buyeo, and Gongju.
Conclusions
To enhance climate–health literacy and community engagement, furthering stratifying vulnerable groups at risk of heat-related illnesses and developing customized health guidance materials are essential measures. In addition, community-based and ferderalized-/resident-based education and risk communication strategies grounded in regional statistical data are required to promote active participation and awareness at the local level.
Keywords: Climate change, Heat wave, Regional statistics, Chronic disease, Health policy
Key messages
① What is known previously?
Although the incidence of heat-related illnesses has increased steadily in the past five years, in-depth regional analyses that consider geographic and sociodemographic characteristics remain limited.
② What new information is presented?
In 2025, the peak period of heat-related illnesses and estimated deaths shifted earlier—from August to July, indicating an earlier heat risk. Approximately 45% of patients presented with underlying conditions, primarily cardiovascular diseases and diabetes, with increased comorbidity rates throughout the surveillance period. Regional disparities in heat-related and chronic disease patterns were identified across the Chungcheong region.
③ What are implications?
This study provides regional climate–health statistics for identifying climate–heat vulnerability to provide support for vulnerable populations, disparity analyses, targeted prevention strategies, and awareness efforts.
Introduction
Heatwaves are a major health risk factor attributable to climate change, and the magnitude and patterns of health impacts vary according to regional and sociodemographic characteristics [1]. In recent years, both the frequency and intensity of extreme climate events have increased [2], and heatwaves have shown characteristics of earlier onset and prolonged duration. On the Korean Peninsula, unlike the previous year when the period of intense heat began in late July, an early heatwave began in late June and persisted until late August in 2025 [3]. In response, several countries have implemented and operated heat-related illness surveillance systems and heatwave response monitoring based on community resources [4-7].
The UK Health Security Agency operates the national Emergency Department Syndromic Surveillance System, which monitors various syndromes, including heat-related illnesses as well as cardiovascular and respiratory diseases. In collaboration with the Met Office, heatwave levels are classified into stages, and early warnings of health risks caused by heatwaves are issued [4].
In the United States, the Center for Disease Control and Prevention and National Oceanic and Atmospheric Administration operate the Heat and Health Initiative. Through this initiative, they provide information to both the public and healthcare professionals by predicting and visualizing heat-related health risk levels for up to seven days. This includes the HeatRisk Forecast Tool, HeatRisk Dashboard, and Clinical Guidance [5].
In 2021, Japan introduced a nationwide heat stroke alert system, under which specific measures, such as refraining from outdoor activities and canceling sporting events, are implemented when the Wet-Bulb Globe Temperature reaches or exceeds 33℃ or 35℃. In addition, the Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications of Japan collects and provides daily and weekly data on the number of heat-related illness transports by emergency services nationwide through the “Heatstroke Surveillance” system from May to September each year [6]. Based on these data, regional risk levels are rapidly identified and used as a basis for preventive measures by local governments and for issuing public alerts [7].
The Korea Disease Control and Prevention Agency (KDCA) operates the Heat-Related Illness Emergency Department Surveillance System during the summer, providing timely information on heat-related illness cases nationwide to raise awareness and promote preventive actions aimed at minimizing health impacts from heatwaves. However, regional disparities exist due to differences in heat exposure environments, healthcare accessibility, and response capacity. Therefore, community-based analyses are needed to strengthen regional preparedness for heatwaves and enhancing adaptive capacity to climate change.
Community-based analyses related to heat-related illness have been conducted at the small-area or national level through analyses of patient incidence data [8,9]. However, comparative analyses of regional disparities at the broader regional level remain relatively insufficient. The Chungcheong region has a higher proportion of older adults than the national average [10,11], and Daejeon, Sejong, Chungcheongnam-do, and Chungcheongbuk-do differ substantially in sociodemographic characteristics and include a mix of urban and rural areas, resulting in considerable geographic heterogeneity. Accordingly, in-depth analyses that take these characteristics into account are necessary.
This study aimed to analyze climate vulnerability and identify health disparities in the Chungcheong region using data from the KDCA Heat-Related Illness Emergency Department Surveillance System. Through an in-depth analysis of heat-related illness incidence at the regional level (four metropolitan/provincial units and 36 municipalities), this study sought to identify vulnerable areas and at-risk populations, develop prioritized and tailored prevention and communication strategies, and provide baseline data to enhance regional health equity.
Methods
This study utilized data from the KDCA Heat-Related Illness Emergency Department Surveillance System conducted in 2025. The system operates annually from May to September with the voluntary participation of approximately 500 medical institutions nationwide, reporting cases of heat-related illness among patients visiting emergency departments. The reported data are collected and aggregated following approval by the relevant public health centers and metropolitan/provincial governments, and daily updates on heat-related illness incidence are provided through the KDCA website. In 2025, in alignment with the operating period of the government-wide comprehensive heatwave response plan, the surveillance period began on May 15, five days earlier than the previous surveillance period (May 20 to September 30), and was terminated early on September 25. For the calculation of regional statistics and in-depth analysis of heat-related illness in the Chungcheong region, in addition to the reported data on heat-related illness occurrence, the scope of information was expanded to include regional-level data (four metropolitan/provincial units and 36 municipalities) on comorbidity status, trends in occurrence, and treatment outcomes. In addition, database data—including disease statistics from the Health Insurance Review and Assessment Service and distribution of heat-related illness occurrence according to daily maximum temperature (℃)—were linked and utilized for analysis. For the analysis of the regional occurrence of heat-related illness in the Chungcheong region, the number of heat-related illness cases by region was divided by the population of the corresponding region (based on resident registration population statistics from the Ministry of the Interior and Safety as of June 2025) to calculate the number of cases per 100,000 population. To facilitate intuitive identification of the distribution of occurrence, hexagon-binning visualization analysis was applied. Information on comorbidities was collected in accordance with the reporting form of the Heat-Related Illness Emergency Department Surveillance System. The reporting form categorizes comorbidities into diabetes, cerebrovascular diseases (cerebral hemorrhage, cerebral infarction), cardiovascular diseases (hypertension, heart failure, myocardial infarction, angina, arrhythmia, etc.), endocrine disorders (hyperthyroidism, hypothyroidism, hyperadrenocorticism, adrenal insufficiency, etc.), cancer, dementia, others, none, and unknown, with multiple responses allowed. In this study, “none” was reclassified as absence of comorbidity, and all other items were reclassified as presence of comorbidity. The types of comorbidities included diabetes, cerebrovascular diseases, cardiovascular diseases, endocrine disorders, dementia, and cancer, with additional inclusion of mental disorders and respiratory diseases recorded under “others.” Treatment outcomes were classified as discharge, hospitalization (general ward, intensive care unit), transfer, discharge against medical advice, and death. Among these, discharge refers to cases in which patients returned home after amelioration of symptoms following treatment at the emergency department.
Results
1. Distribution of Heat-related Illness Occurrence according to Region in the Chungcheong Region
The occurrence of heat-related illness was higher in Chungcheongnam-do and Chungcheongbuk-do than in Daejeon and Sejong (Figure 1). In both Chungcheongbuk-do and Chungcheongnam-do, the occurrence of heat-related illness began to increase at 33℃ range and increased sharply at 34℃ range. However, in the ≥33℃ range, the patterns of heat-related illness occurrence differed between Chungcheongbuk-do and Chungcheongnam-do: in Chungcheongbuk-do, 76 cases occurred in the 34℃ range, whereas in Chungcheongnam-do, the highest number of cases (73) occurred in the 35℃ range. In 2024, the highest number of cases occurred in the 33℃ range in Chungcheongbuk-do (85 cases) and in the 34℃ range in Chungcheongnam-do (85 cases), indicating that the distribution of heat-related illness occurrence according to daily maximum temperature (℃) increased compared with the previous year (Supplementary Figure 1A; available online).
Figure 1. Regional incidence of heat-related illness in the Chungcheong region (2025).
Unit: ℃, no. of cases
2. Regional Statistics on Heat-related Illness Occurrence in the Chungcheong Region
In 2025, a total of 527 heat-related illness cases were reported in the Chungcheong region, with males accounting for 426 cases (80.8%), approximately four times higher than females (101 cases, 19.2%; Table 1) [12]. By age group, individuals aged 40–59 years accounted for the largest proportion (171 cases, 32.4%), whereas the proportion of cases aged ≥60 years was 39.6%, representing a decrease of approximately 2.2% compared with the previous year. By region, Chungcheongnam-do (227 cases) and Chungcheongbuk-do (215 cases) together accounted for approximately 84% of total cases. By type of heat-related illness, heat exhaustion was the most common (358 cases, 67.9%), followed by heat cramps (69 cases, 13.1%) and heat stroke (68 cases, 12.9%). Regarding treatment outcomes, 405 patients (76.9%) were discharged, 89 (16.9%) were hospitalized in general wards, 21 (4.0%) were admitted to intensive care units, 5 (0.9%) died, and 7 (1.3%) were transferred.
Table 1. Regional characteristics of heat-related illness cases in the Chungcheong region.
| Classification | 2024 (n=538) | 2025 (n=527) | Increase/decrease (2025–2024) |
|---|---|---|---|
| Sex | |||
| Male | 418 (77.7) | 426 (80.8) | |
| Female | 120 (22.3) | 101 (19.2) | |
| Age group (yr) | |||
| <20 | 14 (2.6) | 26 (4.9) | 2.3 |
| 20–39 | 120 (22.3) | 121 (22.9) | 0.6 |
| 40–59 | 179 (33.3) | 171 (32.4) | △0.9 |
| 60–79 | 160 (29.7) | 147 (27.9) | △1.8 |
| ≥80 | 65 (12.1) | 62 (11.7) | △0.4 |
| Region of occurrence | |||
| Daejeon | 69 (12.8) | 52 (9.9) | △2.9 |
| Sejong | 29 (5.4) | 33 (6.3) | 0.9 |
| Chungbuk | 196 (36.4) | 215 (43.1) | 6.7 |
| Chungnam | 244 (45.4) | 227 (40.8) | △4.6 |
| Type of heat-related illnessa) | |||
| Heat stroke | 109 (20.3) | 68 (12.9) | △7.4 |
| Heat exhaustion | 303 (56.3) | 358 (67.9) | 11.6 |
| Heat cramps | 71 (13.2) | 69 (13.1) | △0.1 |
| Heat syncope | 47 (8.7) | 26 (4.9) | △3.8 |
| Other | 8 (1.5) | 6 (1.1) | △0.4 |
| Clinical outcome | |||
| Discharged | 414 (77.0) | 405 (76.9) | △0.1 |
| Hospital admission | 79 (14.7) | 89 (16.9) | 2.2 |
| Admission to intensive care unit | 28 (5.2) | 21 (4.0) | △1.2 |
| Death | 6 (1.1) | 5 (0.9) | △0.2 |
| Transfer | 11 (2.0) | 7 (1.3) | △0.7 |
| Comorbidity | |||
| No | 250 (46.5) | 291 (55.2) | 8.7 |
| Yesb) | 288 (53.5) | 236 (44.8) | △8.7 |
| Cardiovascular disease | 150 (27.9) | 153 (29.0) | 1.1 |
| Diabetes mellitus | 80 (14.9) | 73 (13.9) | △1.0 |
| Cerebrovascular disease | 23 (4.3) | 11 (2.1) | △2.2 |
| Neurological disease | 4 (0.7) | 8 (1.5) | 0.8 |
| Renal disease | 16 (3.0) | 22 (4.2) | 1.2 |
| Cancer | 10 (1.9) | 25 (4.7) | 2.8 |
| Mental disorder | 3 (0.6) | 5 (0.9) | 0.3 |
| Respiratory disease | 2 (0.4) | 2 (0.4) | 0.0 |
| Month of occurrence | |||
| May | 3 (0.6) | 6 (1.1) | 0.5 |
| June | 59 (11.0) | 51 (9.7) | △1.3 |
| July | 93 (17.3) | 300 (56.9) | 39.6 |
| August | 325 (60.4) | 157 (29.8) | △30.6 |
| September | 58 (10.8) | 13 (2.5) | △8.3 |
| Place of occurrencec) | |||
| Indoors | 108 (20.1) | 103 (19.5) | △0.6 |
| Outdoors | 430 (79.9) | 424 (80.5) | 0.6 |
| Day of week | |||
| Weekday | 380 (70.6) | 368 (69.8) | △0.8 |
| Weekend | 158 (29.4) | 159 (30.2) | 0.8 |
Unit: no. of cases (%), percentage point change. △=decrease. a)Types of heat-related illnesses (based on the Heat Injury Surveillance System reporting form) [16]: heat stroke: core temperature ≥40℃ with neurological impairment; heat exhaustion: core temperature of 38–40℃ without altered mental status, accompanied by dehydration and generalized weakness; heat syncope: transient loss of consciousness due to peripheral vasodilation and orthostatic hypotension; heat cramps: painful muscle spasms due to electrolyte imbalance from excessive sweating; others: heat edema, other effects of heat and light, and unspecified effects of heat and light. b)As multiple comorbidities could be reported per individual, percentages may not reach a total 100% or exceed 100%. c)Indoor locations include buildings, greenhouses, indoor workplaces, and other indoor spaces; outdoor locations include construction sites, roads, farmland, forests, and outdoor workplaces (including transportation facilities), residential areas, and other outdoor spaces.
A total of 44.8% of patients had one or more underlying conditions, and the major types of underlying diseases were cardiovascular diseases (29.0%) and diabetes (13.9%). The occurrence of heat-related illness was concentrated in July (300 cases, 56.9%) and August (157 cases, 29.8%), indicating that the timing of occurrence was advanced by approximately one month compared with 2024, when cases were concentrated in August (325 cases, 60.4%). The place of occurrence was predominantly outdoors (80.5%, 424 cases), approximately four times higher than indoors (19.5%, 103 cases). The proportion of cases occurring on weekdays was 69.8% (368 cases), approximately 2.3 times higher than on weekends (159 cases, 30.2%).
3. Heat-related Illness Occurrence by Municipality in the Chungcheong Region
In 2025, disparities in heat-related illness incidence across municipalities ranged from 2.3 per 100,000 population in Dong-gu, Daejeon, to 49.6 per 100,000 population in Okcheon County, Chungcheongbuk-do, representing approximately a 21.6-fold difference (Figure 2). In 2005, in Chungcheongnam-do, the areas with the highest incidence remained the same as the previous year—Cheongyang County (40.9), Yesan County (25.4), and Dangjin City (23.8). In contrast, in Chungcheongbuk-do, the areas with the highest incidence were Okcheon County (49.6), Danyang County (40.6), and Boeun County (36.2), and the ranking of these areas was reversed compared with the previous year (Supplementary Figure 1B; available online). In Daejeon, the incidence in Jung-gu, which had been among the highest in 2024, decreased from 8.5 to 4.4 in 2025, whereas Sejong recorded 8.4, similar to 2024. In 2025, estimated deaths from heat-related illness occurred in Dangjin (2 cases), Cheongyang (1 case), Buyeo (1 case), and Gongju (1 case), all located in Chungcheongnam-do; in 2024, five deaths occurred in Chungcheongnam-do and one in Chungcheongbuk-do.
Figure 2. Heat-related illness incidence rates in the Chungcheong region (2025).
Black numbers: Incidence rate of heat-related illness per 100,000 population. Blue numbers: Proportion of heat-related illness patients with comorbidity (%). Red asterisks: Regions with estimated heat-related deaths (Dangjin-si [2], Cheongyang-gun [1], Gongju-si [1], Buyeo-gun [1]).
4. Heat-related Illness Occurrence by Vulnerable Groups in the Chungcheong Region in 2025
To assess vulnerability to heat-related illness occurrence in the Chungcheong region, vulnerable groups among patients with heat-related illness were classified and schematized. Vulnerable groups were categorized into occupational, social, economic, and physical domains, and further subdivided into 16 subgroups, including workplace workers, outdoor workers, recipients of basic livelihood security, and older adults (Supplementary Figure 2; available online).
Among the total 527 patients with heat-related illness, 292 were classified under the occupational category. Within this category, workplace workers accounted for 226 cases (42.8%); followed by agricultural, forestry, and fishery workers (53 cases, 10.1%); military personnel (8 cases, 1.5%); and mobile workers (4 cases, 0.8%; Table 2). In the economic category, recipients of basic livelihood security and homeless individuals accounted for 17 cases (3.2%). In the physical category, older adults aged ≥60 years accounted for 209 cases (39.7%), and individuals with chronic diseases accounted for 236 cases (44.8%).
Table 2. Status of heat-related illness cases occurring in vulnerable occupational settings in the Chungcheong region (2025).
| Classification | Vulnerable groups to heat-related illnesses | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Occupational groups (n=292) | Socioeconomic groups (n=17) |
Physiological groups (n=446) |
|||||||||
| Industrial workersb) (n=226) |
Agricultural and fishery workers (n=53) |
Mobile workers (n=4) |
Foreign workers (n=1) |
Military (n=8) |
Public assistance recipients and peopleexperiencing homelessness (n=17) |
Older adults (n=209) |
People with disabilities (n=1) |
People with chronic diseases (n=236) |
|||
| Age group (yr) | |||||||||||
| 0–9 | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | ||
| 10–19 | 2 (0.9) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | ||
| 20–29 | 27 (11.9) | 2 (3.8) | 0 (0.0) | 0 (0.0) | 8 (100) | 1 (5.9) | 0 (0.0) | 0 (0.0) | 9 (3.8) | ||
| 30–39 | 37 (16.4) | 4 (7.5) | 1 (25.0) | 1 (100) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 12 (5.1) | ||
| 40–49 | 51 (22.6) | 5 (9.4) | 2 (50.0) | 0 (0.0) | 0 (0.0) | 1 (5.9) | 0 (0.0) | 1 (100) | 27 (11.4) | ||
| 50–59 | 48 (21.2) | 8 (15.1) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 6 (35.3) | 0 (0.0) | 0 (0.0) | 41 (17.4) | ||
| 60–69 | 49 (21.7) | 14 (26.4) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 4 (23.5) | 99 (47.4) | 0 (0.0) | 58 (24.6) | ||
| 70–79 | 10 (4.4) | 12 (22.6) | 1 (25.0) | 0 (0.0) | 0 (0.0) | 1 (5.9) | 48 (23.0) | 0 (0.0) | 35 (14.8) | ||
| ≥80 | 2 (0.9) | 8 (15.1) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 4 (23.5) | 62 (29.7) | 0 (0.0) | 54 (22.9) | ||
| ≥65 | 32 (14.2) | 26 (49.1) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 7 (41.2) | 157 (75.1) | 0 (0.0) | 119 (50.4) | ||
| Clinical outcome | |||||||||||
| Discharged | 185 (81.9) | 39 (73.6) | 3 (75.0) | 1 (100) | 2 (25.0) | 11 (64.7) | 148 (70.8) | 1 (100) | 170 (72.0) | ||
| Hospital admission/transfer | 35 (15.5) | 10 (18.9) | 1 (25.0) | 0 (0) | 3 (37.5) | 3 (17.6) | 49 (23.4) | 0 (0.0) | 55 (23.3) | ||
| Admission to intensive care units | 6 (2.7) | 3 (5.7) | 0 (0) | 0 (0) | 3 (37.5) | 2 (11.8) | 9 (4.3) | 0 (0.0) | 8 (3.4) | ||
| Death | 0 (0.0) | 1 (1.9) | 0 (0) | 0 (0) | 0 (0.0) | 1 (5.9) | 3 (1.4) | 0 (0.0) | 3 (1.3) | ||
| Type of heat-related illness | |||||||||||
| Heat stroke | 12 (5.3) | 9 (17.0) | 1 (75.0) | 0 (0) | 4 (50.0) | 11 (64.7) | 39 (18.7) | 1 (100) | 38 (16.1) | ||
| Heat exhaustion | 154 (68.1) | 40 (75.5) | 3 (25.0) | 1 (100) | 4 (50.0) | 6 (35.3) | 141 (67.5) | 0 (0.0) | 162 (68.6) | ||
| Heat syncope | 43 (19.0) | 4 (7.5) | 0 (0) | 0 (0) | 0 (0.0) | 0 (0.0) | 15 (7.2) | 0 (0.0) | 25 (10.6) | ||
| Heat cramps | 13 (5.8) | 0 (0) | 0 (0) | 0 (0) | 0 (0.0) | 0 (0.0) | 11 (5.3) | 0 (0.0) | 9 (3.8) | ||
| Other | 4 (1.8) | 0 (0) | 0 (0) | 0 (0) | 0 (0.0) | 0 (0.0) | 3 (1.4) | 0 (0.0) | 2 (0.8) | ||
| Place of occurrencea) | |||||||||||
| Indoors | 46 (20.4) | 12 (22.6) | 1 (25.0) | 0 (0) | 1 (12.5) | 0 (0.0) | 34 (16.3) | 0 (0.0) | 46 (19.5) | ||
| Outdoors | 180 (79.6) | 41 (77.4) | 3 (75.0) | 1 (100) | 7 (87.5) | 17 (100) | 175 (83.7) | 1 (100) | 190 (80.5) | ||
Unit: no. of cases (%). a)Indoor locations include buildings, greenhouses, indoor workplaces, and other indoor spaces; outdoor locations include construction sites, roads, farmland, forests, and outdoor workplaces (including transportation facilities), residential areas, and other outdoor spaces. b)Vulnerable occupational settings include cases occurring in indoor and outdoor workplaces where heat exposure is expected.
By age group, among workplace workers (226 cases), individuals in their 40s accounted for 22.6%, whereas among agricultural, forestry, and fishery workers, those in their 60s accounted for the largest proportion at 49.1%. Among those aged ≥65 years, workplace workers accounted for 14.2%, whereas agricultural, forestry, and fishery workers accounted for 49.1%. In the economic category, occurrence was concentrated among those aged 50–59 and 60–69, whereas in the physical category, occurrence was high among those aged 60–69 and those aged ≥80 years.
When vulnerable groups were classified by treatment outcomes, more than 90% of cases in most groups were either discharged or hospitalized in general wards, and were, thus, classified as mild or moderate cases. Among military personnel, the proportion of intensive care unit admission was 37.5% of the total 8. In the economic category, recipients of basic livelihood security and homeless individuals showed 11.8% intensive care unit admission and 5.9% mortality. Among older adults, 4.3% were admitted to intensive care units and 1.4% died. Among military personnel and recipients of basic livelihood security or homeless individuals, the proportion of intensive care unit admission was relatively higher compared with other groups. However, interpretation of the results is limited due to the small number of cases.
Regarding the types of heat-related illness, heat stroke and heat exhaustion accounted for more than 80% in all groups, except workplace workers. The proportion of heat stroke was 50% (4 cases) among military personnel and 62.5% (10 cases) among recipients of basic livelihood security and homeless individuals.
The place of occurrence was predominantly outdoors, whereas indoor occurrence was relatively low. In particular, all cases (17 cases) among recipients of basic livelihood security and homeless individuals occurred outdoors.
5. Comparison of Heat-related Illness Occurrence by Type in the Chungcheong Region
In 2025, among the types of heat-related illness in the Chungcheong region, heat exhaustion accounted for 358 (67.9%), heat cramps for 69 (13.1%), and heat stroke for 68 (12.9%; Table 3). Heat exhaustion showed a higher proportion of occurrence in the Chungcheongbuk-do region (47.8%), whereas heat stroke and heat cramps showed the highest proportions in the Chungcheongnam-do region at 58.8% and 60.9%, respectively. In terms of age distribution, among cases of heat stroke, those aged ≥60 years accounted for 57.4% of the total, showing a higher proportion of occurrence among older adults compared with heat exhaustion (39.4%) and heat cramps (21.4%). Regarding the timing of occurrence, heat exhaustion (56.7%), heat stroke (61.8%), and heat cramps (55.1%) were all concentrated in July, and more than 50% occurred during the daytime between 12:00 and 18:00.
Table 3. Comparison of heat-related illness cases by disease type in the Chungcheong region (2025).
| Classification | Heat stroke (n=68) | Heat exhaustion (n=358) | Heat cramps (n=69) |
|---|---|---|---|
| Region of occurrence | |||
| Daejeon | 4 (5.9) | 30 (8.4) | 8 (11.6) |
| Sejong | 5 (7.4) | 21 (5.9) | 5 (7.2) |
| Chungbuk | 19 (27.9) | 171 (47.8) | 14 (20.3) |
| Chungnam | 40 (58.8) | 136 (38.0) | 42 (60.9) |
| Age group (yr) | |||
| 0–19 | 2 (2.9) | 22 (6.1) | 2 (2.9) |
| 20–39 | 13 (19.1) | 88 (24.6) | 12 (17.4) |
| 40–59 | 14 (20.6) | 107 (29.9) | 40 (58.0) |
| 60–79 | 24 (35.3) | 100 (27.9) | 14 (20.3) |
| ≥80 | 15 (22.1) | 41 (11.5) | 1 (1.4) |
| Month of occurrence | |||
| May | 2 (2.9) | 4 (1.1) | 0 (0.0) |
| June | 11 (16.2) | 34 (9.5) | 4 (5.8) |
| July | 42 (61.8) | 203 (56.7) | 38 (55.1) |
| August | 11 (16.2) | 109 (30.4) | 24 (34.8) |
| September | 2 (2.9) | 8 (2.2) | 3 (4.3) |
| Time of occurrence | |||
| 8:00–10:00 | 2 (2.9) | 34 (9.5) | 3 (4.3) |
| 10:00–12:00 | 9 (13.2) | 80 (22.3) | 8 (11.6) |
| 12:00–14:00 | 15 (22.1) | 55 (15.4) | 13 (18.8) |
| 14:00–16:00 | 20 (29.4) | 64 (17.9) | 23 (33.3) |
| 16:00–18:00 | 13 (19.1) | 63 (17.6) | 10 (14.5) |
| After 18:00 | 9 (13.2) | 62 (17.3) | 12 (17.4) |
| Clinical outcome | |||
| Discharged | 34 (50.0) | 294 (82.1) | 52 (75.4) |
| Hospital admission/transfer | 18 (26.5) | 58 (16.2) | 15 (21.7) |
| Admission to intensive care unit | 11 (16.2) | 6 (1.7) | 2 (2.9) |
| Death | 5 (7.4) | 0 (0.0) | 0 (0.0) |
| Comorbidity | |||
| No | 26 (38.2) | 196 (54.7) | 44 (63.8) |
| Yesa) | 42 (61.8) | 162 (45.3) | 25 (36.2) |
| Cardiovascular disease | 19 (27.9) | 91 (25.4) | 15 (21.7) |
| Diabetes mellitus | 18 (26.5) | 46 (12.8) | 7 (10.1) |
| Cerebrovascular disease | 1 (1.5) | 6 (1.7) | 3 (4.3) |
| Neurological disease | 1 (1.5) | 7 (2.0) | 0 (0.0) |
| Renal disease | 3 (4.4) | 15 (4.2) | 0 (0.0) |
| Cancer | 7 (10.3) | 16 (4.5) | 2 (2.9) |
| Mental disorder | 1 (1.5) | 4 (1.1) | 0 (0.0) |
| Respiratory disease | 1 (0.3) | 1 (1.5) | 0 (0.0) |
Unit: no. of cases (%). a)As multiple comorbidities could be reported per individual, percentages may not reach a total of 100% or may exceed 100%.
In the treatment outcome category, most patients with heat exhaustion (82.1%) were discharged, whereas the proportions were 75.4% for heat cramps and 50.0% for heat stroke. When comparing the proportion of comorbidity, 61.8% of patients with heat stroke had comorbidities, showing a higher proportion than heat exhaustion (45.3%) and heat cramps (36.2%). Regarding the types of comorbidities, cardiovascular diseases were most common, followed by diabetes in heat exhaustion, heat stroke, and heat cramps.
6. Trends in Heat-related Illness and Comorbidities in the Chungcheong Region in 2025
In 2025, the number of heat-related illness cases was highest in July (301), followed by August (157) and September (13) (Figure 3). The proportion of patients with heat-related illness with comorbidities exceeded 30% from May, the initial surveillance period, and continued to increase, reaching 53.8% in September. The proportion of cardiovascular disease comorbidity was 16.7% in May and remained above 20% through September, and the proportion of patients with heat-related illness with diabetes increased to 15.3% in August and 30.8% in September.
Figure 3. Trends in major comorbidities among heat-related illness patients by month in the Chungcheong region (2025).
Unit: no. of cases, %
Discussion
Recognizing the severity of climate change and responding to it requires an understanding of climate and health among various stakeholders, including the public, researchers, and policymakers. Climate health literacy has emerged as an important concept, referring to the ability to understand the health impacts of climate change and to translate this understanding into community-level responses and behavioral actions.
The health impacts of heatwaves vary in terms of health damage and patterns according to regional, geographic, and sociodemographic characteristics [13]. Despite recent worker health measures for populations vulnerable to heatwaves (implemented in June 2025) and the comprehensive summer natural disaster countermeasures (May 2025), previous policy research related to heatwaves has been conducted partially for infants and older adults, and research on diverse vulnerable groups remains insufficient.
Accordingly, this study identified the occurrence of heat-related illness in the Chungcheong region (four metropolitan/provincial units and 36 municipalities) and conducted an analysis of regional health disparities. Unlike the existing monitoring results of the Heat-Related Illness Emergency Department Surveillance System (the aggregated number of heat-related illness cases occurring on the previous day), the incidence rate of heat-related illness per 100,000 population was calculated by adjusting for regional population size [14]. Based on these regional statistical results, there are plans to establish and implement community-based participatory and resident-oriented heat-related illness prevention education and communication strategies targeting health-vulnerable areas and vulnerable groups. The Chungcheong region includes metropolitan cities and rural and fishing areas, making it possible to compare disparities according to regional characteristics. Differences in the number of cases by temperature were observed between Chungcheongbuk-do and Chungcheongnam-do. Although the average temperatures of the two regions were similar, differences were identified in the timing and number of days of heatwaves and tropical nights, as well as in the number of precipitation days, precipitation amounts, and heavy rainfall events. Research is needed to analyze psychosociological causes and to assess the current status related to geographic and topographic climatic characteristics and regional disparities.
In the Chungcheong region, occupationally vulnerable groups accounted for approximately 55% of all patients with heat-related illness, and among them, workplace workers accounted for 77.4% of the total occupational group. This is consistent with previous research findings that workers exposed to high-temperature environments for prolonged periods are at risk of heat-related illness [1]. Among agricultural, forestry, and fishery workers, heat-related illness occurrence was higher among older adults aged ≥65 years, whereas the age group with the highest occurrence among workplace workers was middle-aged adults aged 40–49 years. Agricultural, forestry, and fishery workers accounted for the second highest proportion among all occupational groups, reflecting the regional characteristics of the Chungcheong region, where urban and rural areas coexist. Among military personnel, all were in their 20s, and although the number of cases increased by 33% compared with the previous year, the aggregation of case counts was limited. This is consistent with the first academic journal article on military heat-related illness that reported an increase in heat-related illness within military units [15].
In the Chungcheong region, 44.8% of all patients with heat-related illness had comorbidities, and the types of comorbidities were most commonly cardiovascular diseases (29.0%), followed by diabetes (13.9%). The proportion of comorbidity increased continuously from 33.3% in May to 53.8% in September, suggesting the need for continuous heatwave management not only during the intensive heatwave management period of July–August but also from early summer (May–June) through late heat (September) and thereafter. In collaboration with local governments in each region, it is necessary to closely identify local residents with chronic diseases, such as cardiovascular disease or diabetes, and to establish and implement education and communication plans by city, county, and district.
There are limitations in sufficiently explaining the magnitude of occurrence and the distribution of severity of health impacts resulting from heatwaves based solely on surveillance using a single data source. In this study, analysis of disease subcategory statistics by healthcare institution location from the Health Insurance Review and Assessment Service (2020–2024) showed that, among heat-related illnesses, heat exhaustion and heat stroke had higher proportions in that order, and this was similar to the results of the Heat-Related Illness Emergency Department Surveillance System analysis (Supplementary Table 1; available online) [16]. In this regard, the findings of this study suggest the need for research linking and analyzing multi-layered data for heatwave response.
This analysis is meaningful in that it identified and summarized health vulnerability to heat-related illness through the production of regional climate–health statistics at the level of the Chungcheong region (four metropolitan/provincial units and 36 municipalities). However, it has limitations in explaining the overall magnitude and distribution of health impact occurrence resulting from climate change.
In the future, by expanding data sources to include the National Health Insurance Service, Health Insurance Review and Assessment Service, and emergency transport data from the National Fire Agency, in-depth research is needed on the protection of climate–health vulnerable groups and analysis of regional disparity factors and causes, and analytical approaches involving the Community Health Survey and acute cardiac arrest occurrence are also needed.
The regional-level occurrence of heat-related illness in the Chungcheong region and interregional health disparities were quantitatively presented, and it is expected that these results will be utilized to develop community-based participatory and resident-oriented educational content and to enhance community participation and awareness through the training of regional health leaders.
Acknowledgments
None.
Supplementary Materials
Supplementary data are available online.
Declarations
Ethics Statement: Not applicable.
Funding Source: None.
Conflict of Interest: The authors have no conflicts of interest to declare.
Author Contributions: Conceptualization: JYH, YHC. Data curation and Methodology: HYA, HJP. Formal analysis: HYA, HJP. Visualization: HYA, HJP. Writing – original draft: HYA, HJP. Writing – review & editing: JYH, YHC.
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