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.