PHWR Public Health Weekly Report

Despite global warming trends, and despite the fact that the health effects of winter cold waves receive less attention than summer heat waves, health damages from winter cold waves continue to occur [1]. In December 2022, the United States experienced its worst Christmas cold wave in over 40 years, affecting areas ranging from Canada to distant Texas with unprecedented snowstorm impacts. It led to at least 34 deaths nationwide, with New York bearing the brunt of the toll, including over 20 fatalities [2]. Exposure to such cold waves may exacerbate underlying health conditions like respiratory, cardiovascular, and cerebrovascular diseases, potentially leading to increased illness and mortality rates [3]. A study reported the health impacts of climatic elements due to climate change, using daily mortality, meteorological, and air pollution data from 15 European cities between 1990 and 2000; it was found that for every 1°C decrease in temperature, daily mortality increased by 1.35% [4]. From 1973 to 2023, the average number of cold wave days in the Republic of Korea was 6.5 days per winter, showing a slight decrease in frequency, yet cases of cold-related illnesses continue to occur on an annual basis (Figure 1). Early detection and preparation of countermeasures for the onset of cold-related illnesses will be an important role of the Korea Disease Control and Prevention Agency (KDCA) [5].

Figure 1. Number of cold wave days (1973–2023) of winter by year
CRI: cold-related illness.

The KDCA has been running a cold-related illness emergency room surveillance system since 2013, monitoring health damages caused by winter cold waves in approximately 500 emergency rooms nationwide and providing daily data on key occurrence characteristics. Each year from December to February, approximately 500 emergency rooms nationwide (approximately 97% of all emergency rooms) voluntarily participate in reporting cases of cold-related illnesses (hypothermia, frostbite, chilblains, immersion foot/trench foot, etc.) (Table 1). Reported data undergo a process of approval by the local health office and provincial/municipal authorities, after which the KDCA compiles the final surveillance information (Figure 2). The data gathered during the surveillance period is organized by period (daily, cumulative), region (city‧province, city‧county‧district), sex, age, occupation, disease type, time of occurrence, and location of occurrence, and is made available daily at 4 p.m. on the KDCA’s website. This report investigates and analyzes the data using frequency analysis based on the key occurrence characteristics of daily reported cold-related illness surveillance data from December 1, 2022 to February 28, 2023.

Figure 2. Cold-related illness surveillance system flowchart

Table 1 . Reported cases of cold-related illnesses.

Winter season	Total casesa) (estimated no. of death)	Average lowest temperature (℃)	Number of cold wave daysb)
2013–2014 (2013.12.1.–2014.2.28.)	258 (13 deaths)	–3.2	3.3
2014–2015 (2014.12.1.–2015.2.28.)	458 (12 deaths)	–3.6	4.5
2015–2016 (2015.12.1.–2016.2.29.)	483 (26 deaths)	–2.7	5
2016–2017 (2016.12.1.–2017.2.28.)	441 (4 deaths)	–3.2	4.3
2017–2018 (2017.12.1.–2018.2.28.)	631 (11 deaths)	–5.5	11.8
2018–2019 (2018.12.1.–2019.2.28.)	404 (10 deaths)	–3.4	4.9
2019–2020 (2019.12.1.–2020.2.29.)	303 (2 deaths)	–1.4	0.8
2020–2021 (2020.12.1.–2021.2.28.)	433 (7 deaths)	–3.9	7.8
2021–2022 (2021. 12. 1.–2022. 2. 28.)	300 (9 deaths)	–4.8	6.1
2022–2023 (2022. 12. 1.–2023. 2. 28.)	447 (12 deaths)	–4.8	7.0

^a)Total cases including death cases. ^b)Korea Meteorological Administration Open Meteorological Data Portal: Number of days with the lowest morning (03:01~09:00) temperature below –12 degrees Celsius..

1. Meteorological Conditions and Cold-related Illness Reports in Winter 2022–2023

There were 7.0 cold wave days in the winter of 2022–2023 (Dec–Feb), an increase of 0.9 days from the previous year (6.1 days), with significant temperature variability due to continental high pressure and mobile high pressure systems.

During the 2022–2023 season (Dec 1, 2022–Feb 28, 2023), 447 cases of cold-related illnesses including 12 deaths, were reported through the 「Cold-related Illness Emergency Room Surveillance System」, representing a 49.0% increase over the previous year (300 cases, 9 deaths). Based on the date of symptom onset, the monthly distribution of patients was highest in January with 199 cases (44.5%), followed by December with 177 cases (39.6%), and February with 71 cases (15.9%). Owing to a sharp decline in temperature, the coldest period of the winter season 2022–2023 occurred in late January (Jan 20–31, 2023), when 25.7% of all cold-related illnesses occurred (Figure 3).

Figure 3. Occurrence of cold-related illness and temperature (℃) in the 2022–2023 winter season

2. Characteristics of Cold-related Illnesses in Winter 2022–2023

In terms of the demographic characteristics of cold-related illness occurrences, males (303 cases, 67.8%) were more affected than females (144 cases, 32.2%). By age group, the highest number was those in their 80s and older with 102 cases (22.8%), followed by the 60s with 81 cases (18.1%), 50s with 75 cases (16.8%), and 70s with 48 cases (10.7%), with the elderly aged 65 years and over accounting for 42.3% of total cases. The number of cases per 100,000 population was 4.5 for those aged 80 years and older, 1.3 for those in their 70s, 1.1 for those in their 60s, and 0.9 for those in their 50s.

In terms of regional characteristics of cold-related illness cases, Gyeonggi had the most (n=93), followed by Gangwon (n=62), Seoul (n=51), and Chungnam (n=36). The regions with the highest increase compared to the previous year were Daejeon (225.0%), Gyeonggi (151.4%), and Incheon (125.0%), while Jeju showed a 60.0% decrease. Regarding the number of cases per 100,000 population by region, Gangwon reported 4.0 cases, Chungnam 1.7, Chungbuk 1.6, Jeonnam 1.5, and Gyeongbuk 1.3. Regarding the location of occurrence, outdoor incidents accounted for 79.9% (357 cases), while occurrences at home also constituted 14.8% (66 cases). Specifically, the most frequent occurrences were on outdoor streets (111 cases, 24.8%), followed by areas around residences (67 cases, 15.0%), indoors at homes (66 cases, 14.8%), and in mountains (47 cases, 10.5%). The highest frequency occurrence was between 6 and 9 a.m. (80 cases, 17.9%). By occupation, the unemployed constituted the largest group with 151 cases (33.8%), followed by students (45 cases, 10.1%), unskilled laborers (17 cases, 3.8%), and military personnel and homemakers each accounting for 15 cases (3.4%). Cold-related illnesses are classified into two types: systemic and localized diseases. Systemic diseases include hypothermia, while localized diseases include frostbite, chilblains, immersion foot, and trench foot. Of the 447 reported cases of cold-related illness, 300 cases (67.1%) were of systemic diseases like hypothermia, while 147 cases (32.9%) were of localized diseases like frostbite. The total number of reported cold-related estimated fatalities was 12 (7 males, 5 females), all presumed to have died from hypothermia. The average age of the estimated fatalities was 73, with 83% being elderly aged 65 years and over with underlying health conditions. Regionally, Chungbuk reported four deaths, Seoul and Gyeonggi each reported two, followed by Incheon, Chungnam, Daejeon, and Ulsan each reporting one (Table 2).

Table 2 . General characteristics of patients with cold-related illnesses.

Characteristic	Total (n=447)	Focal (n=147)	Systemic (n=300)
Sex
Male	303 (67.8)	118 (80.3)	185 (61.7)
Female	144 (32.2)	29 (19.7)	115 (38.3)
Age (yr)
<10	4 (0.9)	3 (2.0)	1 (0.0)
10–19	36 (8.1)	22 (15.0)	14 (4.7)
20–29	42 (9.4)	33 (22.4)	9 (0.3)
30–39	29 (6.5)	19 (12.9)	10 (3.3)
40–49	30 (6.7)	10 (6.8)	20 (6.7)
50–59	75 (16.8)	22 (15.0)	53 (17.7)
60–69	81 (18.1)	21 (14.3)	60 (20.0)
70–79	48 (10.7)	8 (5.4)	40 (13.3)
≥80	102 (22.8)	9 (6.1)	93 (31.0)
Occupation
Managers	1 (0.2)	0 (0.0)	1 (0.3)
Professionals and related workers	7 (1.6)	6 (4.1)	1 (0.3)
Office workers	14 (3.1)	10 (6.8)	4 (1.3)
Service workers	4 (0.9)	2 (1.4)	2 (0.7)
Sales workers	3 (0.7)	1 (0.7)	2 (0.7)
Skilled agricultural, forestry and fishery workers	5 (1.1)	0 (0.0)	5 (1.7)
Functional personnel and related functional personnel	4 (0.9)	3 (2.0)	1 (0.3)
Equipment, machine operating and assembly workers	3 (0.7)	0 (0.0)	3 (1.0)
Elementary workers	17 (3.8)	9 (6.1)	8 (2.7)
Armed forces	15 (3.4)	14 (9.5)	1 (0.3)
Homemaker	15 (3.4)	1 (0.7)	14 (4.7)
Student	45 (10.1)	30 (20.4)	15 (5.0)
Unemployed	151 (33.8)	20 (13.6)	131(43.7)
Homeless	11 (2.5)	2 (1.4)	9 (3.0)
Unknown	142 (31.8)	47 (32.0)	95(31.7)
Other	10 (2.2)	2 (1.4)	8 (2.7)
Region
Seoul	51 (11.4)	27 (18.4)	24 (8.0)
Busan	9 (2.0)	4 (2.7)	5 (1.7)
Daegu	8 (1.8)	1 (0.7)	7 (2.3)
Incheon	27 (6.0)	2 (1.4)	25 (8.3)
Gwangju	4 (0.9)	0 (0.0)	4 (1.3)
Daejeon	13 (2.9)	3 (2.0)	10 (3.3)
Ulsan	10 (2.2)	2 (1.4)	8 (2.7)
Sejong	4 (0.9)	4 (2.7)	0 (0.0)
Gyeonggi	93 (20.8)	35 (23.8)	58 (19.3)
Gangwon	62 (13.9)	37 (25.2)	25 (8.3)
Chungbuk	26 (5.8)	7 (4.8)	19 (6.3)
Chungnam	36 (8.1)	6 (4.1)	30 (10.0)
Jeonbuk	16 (3.6)	4 (2.7)	12 (4.0)
Jeonnam	28 (6.3)	4 (2.7)	24 (8.0)
Gyeongbuk	34 (7.6)	8 (5.4)	26 (8.7)
Gyeongnam	22 (4.9)	3 (2.0)	19 (6.3)
Jeju	4 (0.9)	0 (0.0)	4 (1.3)
Occurrence location
Outdoor
Work place	18 (4.0)	16 (10.9)	2 (0.7)
Playground	13 (2.9)	7 (4.8)	6 (2.0)
Farmland	13 (2.9)	3 (2.0)	10 (3.3)
Ski resort	14 (3.1)	14 (9.5)	0 (0.0)
Skating rink	0 (0.0)	0 (0.0)	0 (0.0)
Mountain	47 (10.5)	37 (25.2)	10 (3.3)
Riverside	37 (8.3)	3 (2.0)	34 (11.3)
Roadside	111 (24.8)	27 (18.4)	84 (28.0)
Nearby residence	67 (15.0)	16 (10.9)	51 (17.0)
Other	37 (8.3)	9 (6.1)	28 (9.3)
Indoor
Home	66 (14.8)	10 (6.8)	56 (18.7)
Building	16 (3.6)	2 (1.4)	14 (4.7)
Work place	2 (0.4)	2 (1.4)	0 (0.0)
Other	6 (1.3)	1 (0.7)	5 (1.7)
Time of occurrence
0–3	54 (12.1)	16 (10.9)	38 (12.7)
3–6	47 (10.5)	10 (6.8)	37 (12.3)
6–9	80 (17.9)	16 (10.9)	64 (21.3)
9–12	60 (13.4)	17 (11.6)	43 (14.3)
12–15	55 (12.3)	29 (19.7)	26 (8.7)
15–18	64 (14.3)	26 (17.7)	38 (12.7)
18–21	52 (11.6)	22 (15.0)	30 (10.0)
21–24	35 (7.8)	11 (7.5)	24 (8.0)
Underlying disease
Yes	189 (42.3)	32 (21.8)	157 (52.3)
No	216 (48.3)	110 (74.8)	106 (35.3)
Unknown	42 (9.4)	5 (3.4)	37 (12.3)
Alcohol consumption
Drinker	88 (19.7)	12 (8.2)	76 (25.3)
Nondrinker	269 (60.2)	119(80.9)	150 (50.0)
Unknown	90 (20.1)	16(10.9)	74 (24.7)

Unit: n (%)..

Given the high incidence and mortality rate among the elderly aged 65 years and over, there is a need for tailored health guidelines for the elderly as well as proactive measures through collaboration with relevant ministries and local governments [2]. So, the KDCA is actively providing updates on daily occurrences through its website (www.kdca.go.kr) during the winter (Dec to Feb), and is actively promoting awareness about the health impacts of cold waves through promotional materials such as booklets, posters, leaflets, and infographics. Cold-related illnesses can cause fatalities and injuries if not treated properly, but can be prevented by taking appropriate precautions ahead of time. It is crucial to pay attention to weather forecasts such as cold wave warnings, check the perceived temperature before venturing out, and adhere to cold weather health guidelines such as wearing hats, scarves, gloves, and the like to keep body temperature stable. During cold wave warnings, the KDCA, in particular, is increasing media promotions to disseminate information on the status of health impacts and prevention guidelines, aiming to minimize public health damages. The KDCA intends to continue efforts to promptly provide information on health damages caused by cold waves and ensure the stable operation of the surveillance system through organic collaboration with emergency rooms, health centers, cities, and provinces nationwide.

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