Karōshi (過労死, karōshi?), which can be translated quite literally from Japanese as "death from overwork", is occupational sudden death. Although this category has a significant count, Japan is one of the few countries that reports it in the statistics as a separate category. The major medical causes of karōshi deaths are heart attack and stroke due to stress.
The first case of karōshi was reported in 1969 with the death from a stroke of a 29-year-old male worker in the shipping department of Japan's largest newspaper company. It was not until the latter part of the 1980s, during the Bubble Economy, however, when several high-ranking business executives who were still in their prime years suddenly died without any previous sign of illness, that the media began picking up on what appeared to be a new phenomenon. This new phenomenon was quickly labeled karōshi and was immediately seen as a new and serious menace for people in the work force. In 1987, as public concern increased, the Japanese Ministry of Labour began to publish statistics on karōshi.
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http://en.wikipedia.org/wiki/Kar%C5%8Dshi