Seasonal Variation in Sudden Death among Japanese Workers: Why are There Peaks in Spring and Winter?

Overwork and its Health Effects-Current Status and Future Approach Regarding Karoshi

The word karoshi, i.e. death due to overwork, is not defined for medical diagnosis, but in Japan it means cases of compensation awarded by reason of fatal occupational diseases, particularly ischemic heart diseases and cerebrovascular diseases which are recognized as caused by a heavy workload. Current studies have shown that 1) almost definitely there is evidence of an association between overwork and cardiovascular diseases and the risk factors were found, 2) no reports have been published on evidence of a causal relationship between overwork and fatal effects even though the possibility remains, and 3) the adverse health effects can vary according to workers' characteristics such as gender, age, stress coping and perception. Recently there has been an increase in the proportion of compensated cases versus claims from 3.1% in the 1988 fiscal year to 20.7% in the 2001 fiscal year. This may be related to the deregulation of criteria for compensation, or nintei-kijun. The period of determination of overwork for victims has been extended to a maximum of six months in the newest criteria set in 2001, up from only one week in the criteria set in 1987. According to sociological analysis, long working hours in Japan are related not only to the structure of the working-time system but also the sociocultural background of labor. In 2002, the Japanese government provided the first countermeasures for the prevention of karoshi for all employees stating that they should not work more than 45 h overtime per month and that government intervention in the form of administrative guidance to employees and their employers should be conducted if overtime exceeds 100 h per month. It is a population strategy targeting all workers equally, not just a high-risk strategy targeting only those with some risk factors, and is expected to provide more fruitful results with flexibility, i.e. differentially reinforced management for older workers and those working under highly stressful conditions with harmonization of the production cycle in the workplace. Occupational health professionals such as occupational health physicians and nurses will play a key role in making break-throughs to solve various problems related to karoshi, which may then result in further investigations to provide scientific evidence for policy making.