PHWR Public Health Weekly Report

Global warming involves more than just rising temperatures; it impacts the intricate climate systems, leading to more severe and unpredictable weather events, including more intense and frequent cold waves. Research indicates that the intensity and duration of cold waves are likely to escalate due to climate change [1].

A cold wave is a meteorological event characterized by a sudden drop in winter temperatures. According to the Korea Meteorological Administration, a cold wave day is defined as a day when the minimum morning temperature falls below –12℃ [2].

Cold waves pose significant health risks, leading to conditions such as hypothermia, frostbite, chilblains, immersion disease, and immersion foot. These conditions are particularly severe among vulnerable populations, including the elderly, children, and the homeless [2].

On February 3–4, 2023, the Northeastern United States experienced a record-breaking cold wave, with maximum temperatures plummeting to –44℃ and wind chill temperatures reaching –78℃. This extreme weather resulted in one fatality due to strong winds and led to the closure of public schools in Boston and Worcester, Massachusetts, as well as Buffalo, New York. Simultaneously, neighboring regions in Canada, including New Brunswick, Ontario, and Toronto, also experienced severe cold. In the UK, Scotland recorded a minimum temperature of –15℃ on March 8, 2023, the lowest for March since 2010. Notably, unusual low temperatures were recorded across Japan, China, Taiwan, Myanmar, Afghanistan, and even Australia in Oceania [3]. A multinational study examining the mortality risks associated with ambient temperature found that deaths attributed to cold (7.29%, confidence interval [CI] 7.02–7.49) were significantly higher than those caused by heat (0.42%, CI 0.39–0.44) [4]. Additionally, a 1℃ decrease in temperature was linked to an increase in mortality from respiratory diseases (2.90%, CI 1.84–3.97) and cardiovascular diseases (1.66%, CI 1.19–2.14) [5].

In the Republic of Korea (ROK), the average number of cold wave days each winter from 2013, when the cold-related illness surveillance system was established, to 2023 was 5.3 days. During this period, there has been a consistent occurrence of patients with cold-related illnesses each year. The correlation coefficient between the number of cold wave days and the incidence of cold-related illnesses was notably high at 0.737 (p<0.01) (Figure 1). This study aims to provide crucial foundational data to support the development and implementation of related public health policies in the future by analyzing and disseminating information from the cold-related illness surveillance system operated by the Korea Disease Control and Prevention Agency (KDCA).

Figure 1. Number of cold wave days (2013–2023) and patients with CRI of winter by year
CRI=cold-related illness. *p<0.01.

Since 2013, the KDCA has operated a cold-related illness surveillance system. In the 2023–2024 season, 507 (97.7%) out of 519 medical institutions with emergency departments nationwide (as of December 2023) participated in this system. It targets individuals visiting hospital emergency departments with cold-related illnesses such as hypothermia, frostbite, chilblains, immersion disease, and immersion foot, among others (Table 1). Data reported through the Integrated Disease and Health Management System are managed and operated by obtaining initial approval from the respective public health centers and municipal/provincial governments, followed by final approval from the KDCA. This process culminates in the aggregation of related surveillance information. The collected data, organized by period (daily, cumulative), region (city/province, city/county/district), and major case characteristics (gender, age, occupation, disease, time and location of occurrence), are posted on the KDCA website daily at 4 p.m. This report analyzes data on cold-related illnesses based on these major characteristics, using daily surveillance data from December 1, 2023, to February 29, 2024.

Table 1 Key results of the 2023–2024 seasonal cold-related illnesses surveillance system

Characteristic	Total (%) (n=400)	Focal (%) (n=82)	Systemic (%) (n=318)
Sex
Male	268 (67.0)	67 (81.7)	201 (63.2)
Female	132 (33.0)	15 (18.3)	117 (36.8)
Age (yr)
0–9	7 (1.8)	3 (3.7)	4 (1.3)
10–19	15 (3.8)	5 (6.1)	10 (3.1)
20–29	27 (6.8)	16 (19.5)	11 (3.5)
30–39	26 (6.5)	13 (15.9)	13 (4.1)
40–49	23 (5.8)	7 (8.5)	16 (5.0)
50–59	62 (15.5)	15 (18.3)	47 (14.8)
60–69	69 (17.3)	12 (14.6)	57 (17.9)
70–79	54 (13.5)	7 (8.5)	47 (14.8)
≥80	117 (29.3)	4 (4.9)	113 (35.5)
Occupation
Managers	2 (0.5)	-	2 (0.6)
Professionals and related workers	4 (1.0)	3 (3.7)	1 (0.3)
Office workers	11 (2.8)	4 (4.9)	7 (2.2)
Service workers	9 (2.3)	2 (2.4)	7 (2.2)
Sales workers	3 (0.8)	1 (1.2)	2 (0.6)
Skilled agricultural, forestry and fishery workers	6 (1.5)	1 (1.2)	5 (1.6)
Functional personnel and related functional personnel	-	-	-
Equipment, machine operating and assembly workers	4 (1.0)	4 (4.9)	-
Elementary workers	6 (1.5)	1 (1.2)	5 (1.6)
Armed forces	10 (2.5)	8 (9.8)	2 (0.6)
Homemaker	18 (4.5)	1 (1.2)	17 (5.3)
Student	20 (5.0)	9 (11.0)	11 (3.5)
Unemployed (excluded homeless)	147 (36.8)	7 (8.5)	140 (44.0)
Homeless	6 (1.5)	2 (2.4)	4 (1.3)
Unknown	141 (35.3)	35 (42.7)	106 (33.3)
Other	13 (3.3)	4 (2.4)	9 (2.8)
Underlying disease
Yes	231 (57.8)	25 (30.5)	206 (64.8)
No	169 (42.3)	57 (69.5)	112 (35.2)
Unknown	-	-	-
Alcohol consumption
Drinker	85 (21.3)	7 (8.5)	78 (24.5)
Non-drinker	221 (55.3)	61 (74.4)	160 (50.3)
Unknown	94 (23.5)	14 (17.1)	80 (25.2)
Region
Seoul	36 (9.0)	8 (9.8)	28 (8.8)
Busan	14 (3.5)	-	14 (4.4)
Daegu	8 (2.0)	1 (1.2)	7 (2.2)
Incheon	37 (9.3)	7 (8.5)	30 (9.4)
Gwangju	1 (0.3)	-	1 (0.3)
Daejeon	7 (1.8)	-	7 (2.2)
Ulsan	7 (1.8)	1 (1.2)	6 (1.9)
Sejong	3 (0.8)	2 (2.4)	1 (0.3)
Gyeonggi	74 (18.5)	26 (31.7)	48 (15.1)
Gangwon	58 (14.5)	25 (30.5)	33 (10.4)
Chungbuk	22 (5.5)	4 (4.9)	18 (5.7)
Chungnam	26 (6.5)	2 (2.4)	24 (7.5)
Jeonbuk	19 (4.8)	1 (1.2)	18 (5.7)
Jeonnam	13 (3.3)	3 (3.7)	10 (3.1)
Gyeongbuk	44 (11.0)	2 (2.4)	42 (13.2)
Gyeongnam	25 (6.3)	-	25 (7.9)
Jeju	6 (1.5)	-	6 (1.9)
Occurrence location
Outdoor
Work place	11 (2.8)	8 (9.8)	3 (0.9)
Playground (park)	9 (2.3)	2 (2.4)	7 (2.2)
Farmland	8 (2.0)	-	8 (2.5)
Ski resort	3 (0.8)	3 (3.7)	-
Skating rink	-	-	-
Mountain	37 (9.3)	26 (31.7)	11 (3.5)
Riverside, beach	38 (9.5)	1 (1.2)	37 (11.6)
Roadside	86 (21.5)	9 (11.0)	77 (24.2)
Nearby residence	57 (14.3)	10 (12.2)	47 (14.8)
Other	50 (12.5)	11 (13.4)	39 (12.3)
Indoor
Home	72 (18.0)	5 (6.1)	67 (21.1)
Building	11 (2.8)	2 (2.4)	9 (2.8)
Work place	5 (1.3)	4 (4.9)	1 (0.3)
Other	13 (3.3)	1 (1.2)	12 (3.8)
Time of occurrence
0–3	42 (10.5)	8 (9.8)	34 (10.7)
3–6	49 (12.3)	3 (3.7)	46 (14.5)
6–9	75 (18.8)	9 (11.0)	66 (20.8)
9–12	63 (15.8)	17 (20.7)	46 (14.5)
12–15	45 (11.3)	15 (18.3)	30 (9.4)
15–18	53 (13.3)	14 (17.1)	39 (12.3)
18–21	38 (9.5)	9 (11.0)	29 (9.1)
21–24	35 (8.8)	7 (8.5)	28 (8.8)

During the 2023–2024 season (December 1, 2023–February 29, 2024), the ‘cold-related illness surveillance system’ reported a total of 400 patients with cold-related illnesses, including 12 deaths. This represents a 10.5% decrease in cases compared to the previous year, which saw 447 patients and 12 deaths. The monthly breakdown of cases based on the date of symptom onset shows the highest number in January with 196 (49.0%), followed by 127 (31.8%) in December, and 77 (19.3%) in February. The coldest period of the 2023–2024 winter season occurred from January 20 to January 31, 2024, during which 18.8% of all cold-related illnesses were reported, attributed to a significant drop in temperature (Figure 2).

Figure 2. Current status of cold-related illness and average lowest temperature distribution for the 2022–2024 winter seasons
(A) 2022–2023 season, (B) 2023–2024 season. CRI=cold-related illness.

Regarding the weather conditions for the 2023–2024 winter season (December to February) in ROK, the overall temperature was higher than average due to a high-pressure system from the east and frequent warm southerly winds [6]. The average minimum temperature was –1.9℃, higher than the 10-year average of –3.7℃. Additionally, the number of cold wave days was 3.1, a decrease from the 10-year average of 5.6 days. The reported 400 cases of cold-related illnesses were lower than the 10-year average of 416, while the number of deaths remained consistent with the 10-year average of 12 (Table 2) [7].

Table 2 Results of the emergency room surveillance system for cold-related illnesses by season over the past five years

Winter season	Total casesa) (estimated no. of death)	Average lowest temperature (℃)	No. of cold wave daysb)
2013–2014 (2013. 12. 1.–2014. 2. 28.)	258 (13)	–3.2	3.3
2014–2015 (2014. 12. 1.-2015. 2. 28.)	458 (12)	–3.6	4.5
2015–2016 (2015. 12. 1.-2016. 2. 29.)	483 (26)	–2.7	5
2016–2017 (2016. 12. 1.-2017. 2. 28.)	441 (4)	–3.2	4.3
2017–2018 (2017. 12. 1.-2018. 2. 28.)	631 (11)	–5.5	11.8
2018–2019 (2018. 12. 1.-2019. 2. 28.)	404 (10)	–3.4	4.9
2019–2020 (2019. 12. 1.-2020. 2. 29.)	303 (2)	–1.4	0.8
2020–2021 (2020. 12. 1.-2021. 2. 28.)	433 (7)	–3.9	7.8
2021–2022 (2021. 12. 1.-2022. 2. 28.)	300 (9)	–4.8	6.1
2022–2023 (2022. 12. 1.-2023. 2. 28.)	447 (12)	–4.8	7.0
Average of the last 10 years	416 (12)	–3.7	5.6
2023–2024 (2023. 12. 1.-2024. 2. 29.)	400 (12)	–1.9	3.1

^a)Total cases including death cases. ^b)Korea Meteorological Administration Open Meteorological Data Portal: number of days with the lowest morning temperature (03:01–09:00) below –12 degrees Celsius. Reused from the report of Lee et al. (Public Health Wkly Rep 2024;17:167-80) [7]..

Examining the occurrence of cold-related illness by the main characteristics of the cases revealed distinct patterns. In terms of sex, male accounted for a higher number of cases (268, 67.0%) compared to female (132, 33.0%). Age-wise, the highest incidence was among the elderly aged 80 years or older, with 117 cases (29.3%), followed by those in their 60s with 69 cases (17.3%), those in their 50s with 62 cases (15.5%), and those in their 70s with 54 cases (13.5%). Notably, patients aged 65 years or older comprised 51.5% of all cases. The incidence per 100,000 people was 5.1 in those aged 80 years or older, 1.4 in those in their 70s, 0.9 in those in their 60s, and 0.7 in those in their 50s. Regarding occupation, the unemployed represented the largest group affected, with 147 cases (36.8%), followed by students with 20 (5.0%) and housewives with 18 (4.5%). Among these patients, 231 (57.8%) had underlying diseases. Regarding the type of cold-related illness, 318 (79.5%) of the 400 reported cases had systemic diseases like hypothermia, while 82 (20.5%) had focal conditions such as frostbite. Geographically, Gyeonggi reported the highest number of cases with 74, followed by Gangwon with 58, Seoul with 36, and Chungnam with 26. The incidence per 100,000 people was highest in Gangwon at 3.8, followed by Gyeongbuk at 1.7, Chungbuk at 1.4, and both Incheon and Chungnam at 1.2. Most cases occurred outdoors (74.8%, n=299), while 14.8% (n=66) occurred inside homes. The highest number of outdoor cases was roadside (86, 21.5%), followed by inside homes (72, 18.0%), and near residences (57, 14.3%). Most cases occurred between 6 a.m. and 9 a.m. (n=75, 18.8%) (Table 1). The total number of deaths presumed to be due to cold-related illness was 12 (5 males, 7 females), with hypothermia suspected as the main cause. The average age of the deceased was 77.4 years, with 75.0% being elderly individuals aged 65 years or older with underlying diseases. Regionally, there were 4 deaths in Gangwon, and one each in Incheon, Gyeonggi, Chungbuk, Chungnam, Jeonbuk, Jeonnam, Gyeongbuk, and Busan (Table 3).

Table 3 Status of reported deaths due to cold-related illnesses in the 2023–2024 season

No.a)	Region	Sex	Age (yr)
1	Gangwon	Male	98
2	Gangwon	Male	56
3	Gangwon	Female	40
4	Gyeongbuk	Female	92
5	Chungnam	Female	88
6	Gyeonggi	Female	83
7	Jeonbuk	Female	94
8	Chungbuk	Male	51
9	Gangwon	Female	79
10	Jeonnam	Female	88
11	Busan	Male	76
12	Incheon	Male	84

^a)The serial number is in order of the report date..

The occurrence of cold-related illnesses and associated deaths can be prevented with appropriate measures. However, inadequate preventive actions can result in loss of life. It is crucial to heed cold wave alerts and weather forecasts, check the wind chill temperature before going outdoors, and adhere to health guidelines for cold waves, such as wearing hats, scarves, and gloves. During the winter months (December to February), the KDCA promptly updates the status of health impacts from cold waves on its website (www.kdca.go.kr) at 4 p.m. daily. After the surveillance period, it publishes an annual report on reported cases of cold-related illnesses to provide foundational data for responding to and developing policies for cold waves. Additionally, the KDCA produces informational materials such as posters, card news, and booklets to proactively educate the public about the health impacts of cold waves and the necessary precautions. The agency also strengthens its media relations by issuing press releases about the current status of health impacts from cold waves and preventive guidelines when forecasts predict significant cold wave impacts.

This study revealed that cold-related illnesses and suspected deaths predominantly affect the elderly, aged 65 and older. To address this issue, it is vital to tailor health guidelines for the elderly during the winter and foster collaboration between related ministries and local governments [2]. Moving forward, the KDCA plans to actively collaborate with hospital emergency departments, public health centers, and municipal and provincial governments nationwide to ensure the efficient operation of the surveillance system, thereby facilitating prompt dissemination of information on health impacts from cold waves.

Ethics Statement: Not applicable.

Funding Source: None.

Acknowledgments: None.

Conflict of Interest: The authors have no conflicts of interest to declare.

Author Contributions: Conceptualization: YJA, DSA. Formal analysis: JHL. Methodology: JHL. Visualization: JHL. Writing – original draft: JHL. Writing – review & editing: YJA, DSA