It is well known that the Japanese love to unwind in hot baths, but what perhaps is not so well known is that about 14,000 people die each year from taking them.

The death toll tends to rise in the winter, and many of the victims are elderly. Some physicians have listed the cause of death as heart attacks or strokes, but the exact reason remains unclear.

Heatstroke can indeed occur when taking hot baths, according to Shingo Hori, a Keio University assistant professor who specializes in emergency medicine.

Hori, who leads a group of researchers who have examined bath-stricken patients at Keio University Hospital in Tokyo, recently reported their findings at a Saitama seminar.

Masaru Suzuki, an assistant to Hori, said that while strokes or heart attacks cannot be ruled out, they can't be blamed for causing all bath-induced deaths.

For the most part, the patients didn't show unusual symptoms. However, those who had high body temperatures showed changes in blood pressure and consciousness.

In the group's experiments, one subject was initially soaked in a bath heated to a temperature of 44 degrees. His temperature soared to 40 degrees in 10 minutes.

The group then anesthetized mice and placed them in water heated to between 40 and 45 degrees to observe changes in their body temperature and breathing.

A mouse in 40-degree water passed out but came to after a while. But mice placed in hotter water stopped breathing in 30 minutes to two hours and never regained consciousness.

The group found the amount of blood pumped by the heart fell when a mouse was kept in hot water a long time, and its blood vessels -- which are supposed to expand -- actually contracted.

Mice have a body temperature of 38 degrees and do not perspire, but Hori's group concluded humans may experience the same effects and sudden death can occur from being overheated in a bath.