The number of heatstroke patients in South Korea has more than tripled over the past four years, new data show.
The Health Insurance Review and Assessment Service said heatstroke cases surged 208.4%, from 1,793 in 2020 to 5,529 last year.
Over the same period, total hospital visit days for heat-related illness patients jumped 163.6%, from 4,068 to 10,725, while total national health insurance treatment costs rose 277.3%, from 1.07 billion won ($742,000) to 4.04 billion won.
Heatstroke is one of the most severe forms of heat-related illness, a category of acute conditions caused by exposure to high temperatures.
Heatstroke patients typically have a core body temperature — the temperature of the body's internal organs — exceeding 40 degrees Celsius, and suffer central nervous system dysfunction including altered consciousness, delirium and seizures.
In some cases, heatstroke can be diagnosed even when core temperature remains below 40 degrees Celsius. In those situations, the most critical warning sign is a change in consciousness.
Among heatstroke patients recorded between 2011 and 2025, about 44% experienced altered consciousness — including impaired consciousness (31.1%), loss of consciousness (11.6%) and death (1.4%). By contrast, more than 90% of patients with heat exhaustion, heat cramps or heat syncope remained fully conscious.
Heatstroke can be fatal if not treated promptly.
Of the 267 heat-related deaths recorded through the Korea Disease Control and Prevention Agency's emergency room heat illness surveillance system between 2011 and 2025, 256 — or 95.8% — were attributed to heatstroke.
During that period, heatstroke accounted for 21.6% of all heat-related illness cases yet carried a fatality rate of 4.4% — far higher than the 0.04% rate for heat exhaustion, a more commonly occurring heat-related condition.
All 13 estimated heat-related deaths recorded this year as of Thursday are also believed to have involved heatstroke as a contributing factor.
Of the 13 victims, 11 — or 84.6% — were aged 65 or older.
Kim Jun-seong, a professor in the emergency medicine department at Asan Medical Center in Seoul, said older adults are less able to respond accurately to changes in body temperature. "It is as if their thermostat is broken — the body's cooling system does not activate in time," he said.
Heatstroke typically begins with mild symptoms but can deteriorate rapidly depending on the individual and circumstances.
The first warning sign is excessive fatigue — tiring more easily than usual, a drop in energy and difficulty with simple activities. Resting and rehydrating at this stage can prevent the condition from worsening.
Headache and dizziness are also important early symptoms. Patients may complain of a heavy head, dizziness or blurred vision, and can lose their sense of balance and begin to stagger.
As body temperature rises further, the skin becomes hot and flushed while, paradoxically, sweating nearly stops.
Kim said this is "a signal that the body's temperature-regulation system has completely broken down — a situation that requires immediate emergency treatment."
He added that "heatstroke will not occur as long as you avoid exposure to extremely hot environments," and urged the public to avoid going outside as much as possible when a heat wave advisory is issued — and, if they must go out, to do so in the early morning or late evening.
woo@heraldcorp.com
