Although heatstroke draws more public attention, hypothermia kills around 1,000 people almost every winter in Japan, or 1.5 times the number of deaths caused by heat-related maladies, medical and weather experts warn.

Many of the patients are seniors stricken by isolation and poverty, they say.

Hypothermia occurs when the inner body temperature falls below 35 degrees. Contrary to general belief, it can often strike while a person is indoors.

On a freezing day in late January, an unconscious woman in her 80s was rushed to the emergency room at Teikyo University Hospital in Tokyo’s Itabashi Ward. The woman, who lived alone and had dementia, was in a state of shock with a body temperature of 26 degrees. A neighbor called for an ambulance after finding her groggy inside her home.

“This is a typical case of an elderly person who develops hypothermia. We accept such patients almost every day,” said Yasufumi Miyake, a professor of emergency medicine at the hospital.

Hypothermia killed about 16,000 people between 2000 and 2016, according to Health, Labor and Welfare Ministry statistics.

A survey four years ago by the Japanese Association for Acute Medicine found that of the 705 people taken to 91 emergency medical units across the country, more than 70 percent, or 517, developed hypothermia while indoors.

The average age of the patients was 72.9. Many had high blood pressure, diabetes or mental disorders. In the end, 161 of them died.

The patients lived not only in the north, where temperatures often fall below zero, but also in the western and southwestern parts of the country, which are considered relatively warm.

Miyake said one of the major causes of hypothermia is lack of nutrition, particularly among elderly people in poverty and isolation. “Nobody notices patients until their symptoms get serious,” he said.

Fumiaki Fujibe, a professor of meteorology at Tokyo Metropolitan University, said hypothermia used to cause around 400 deaths a year until the 1980s. After climbing, it began to soar in the 1990s as the population grayed.

“Compared with heatstroke, deaths by hypothermia have not drawn much attention, and the whole picture of the victims has not been clarified, Fujibe said. “We have to study the current situation and take countermeasures.”

KEYWORDS medicine, health, hypothermia