Accumulated Fatigue May be Considered in the Standards for the Recognition
of " Karoshi "
The Expert Examination Meeting of the Ministry of Health, Labor and Welfare
(MHLW) gave an outline of a new standards to recognize workers dying from
so-called "karoshi" (death due to excessive work) being caused
by cerebrovascular or ischemic heart diseases (excluding those attributable
to accidental injuries) for the workers' accident compensation insurance.
(1) Cerebro-cardio diseases generally appear
as a natural process during which pathologic changes develop in blood vessels
and continue to progress in aging. However, there are cases in which heavy
job-related burdens cause such pathologic changes in blood vessels to become
significantly aggravated beyond the natural progressive process, resulting
in severe cerebro-cardio diseases.
(2) As the "accumulation of long-term fatigue" may
effect the appearance of cerebro-cardio diseases, the accumulation of fatigue
due to long-term work (long-term, excessive burdens) should be considered
as a severe and obvious job-related burden, in addition to those burdens
that occur during a time period close to the appearance of cerebro-cardio
diseases (abnormal events and excessive short-term burdens).
(3) For supporting the recognition process of a care, it is
proper to select a worker in good health condition of similar age, experiences,
etc., and a worker who are suffering from the diseases, but he is working
without any hindrance.
2. Comprehensive Evaluation of the Excessively Heavy Work Burdens
(1) Long-term excessive work burdens
A. It is reasonable to evaluate the excessively heavy work
burdens by specifically and objectively observing working conditions and situations
during the six months before the appearance of the relevant cerebro-cardio disease
in order to determine whether accumulated fatigue during such period of time
is considered to have aggravate pathologic blood vessel changes beyond the natural
process, and result in the appearance of such disease.
B. More specifically, by considering the corelation with
the relevant worker's working hours, irregularity of work, work-related
restrictions on movement, shift work, working environments and other factors
(including the incidence of mental stress) arising from work, a worker
may be judged to have undergone excessive burdens when a co-worker of similar
age and experience is considered to have experienced such heavy physical
or mental burdens.
- C. With respect to working hours, which are considered to be one
of the most important factors causing accumulated fatigue:
(1) A strong corelation can be assumed between an employee's
work and the appearance of a certain disease, if such employee experiences
overtime working hours in excess of about 100 hours during the month prior
to such appearance, or overtime working hours in excess of about 80 hours
per month during the time period of two to six months before such appearance.
- (2) During a time period of one to six months before the appearance,
(a) if such worker has not experienced overtime-working hours in
excess of about 45 hours per month, a corelation between an employee's
work and the appearance of a certain disease is considered weak;
(b) the longer such worker's overtime working hours become
in excess of about 45 hours per month, the stronger the corelation between
the employee's work and the appearance of a certain disease is assumed.
- D. Factors other than working hours include the following
(see the Appendix for specific examples):
(1) Irregular working hours
(2) Long working hours without leave from working place
(3) Frequent business trips
(4) Shift work and late-night work
(5) Working environments (temparature, noise, jet-lag)
(6) Work-related stress (psychological stress)
(2) Excessive work burdens in a short
period due to abnormal or irregular work situations.
An assumption that obviously
excessive burdens due to the work during the period of time close to the appearance
of cerebro-cardio diseases can be a direct cause of such diseases in the light
of current medical knowledge. Accordingly, the current standards for the recognition
can also be considered reasonable.
3. Risk Factors causing
Risk factors such as
hypertension, hyperlipemia, and/or smoking are affecting the appearance of cerebro-cardio
diseases, and those who have multiple factors are subject to a higher risk of
the diseases. As such, it is necessary to adequately understand worker health
conditions, to fully examine the extent of underlying diseases and of heavy
work burdens, and to make comprehensive judgments on the corelation between
these factors and cerebro-cardio diseases occurring in workers.
Factors other than excessive overtime
Viewpoints to Evaluate Burdens
Frequency and extent of changes in
work schedule, advance notifications, extent of expectations and extent
of changes in work contents.
Long working hours of restricted
Work contents, work intensity (ratio
of actual working hours to waiting hours), rest time and naptime, resting
and napping facilities (space, air-conditioning and noises, etc.).
Frequent business trips
Work contents at business trips,
frequency of such trips (especially overseas trips involving time differences),
transportation, traveling hours and conditions, need for hotel stays,
hotel facilities, whether adequate resting time including sleeping time
is secured, and whether recovery from fatigue during trips is possible
Shift work and late-night work
Extent of changes in work shifts,
period of time between shifts, and frequency of late-night work during
Whether a worker
feels pains in hands or legs or severe shivering due to work in cold environments,
whether a worker has put on clothing for cold weather with appropriate
heat-retention capabilities suitable to the work intensity and surrounding
temperatures, whether a worker can warm up during a series of such work
assignments, and whether a worker is alternatively exposed to excessively
warm and cold temperatures or must frequently enter into and exit from
locations with a substantial difference in temperatures.
Whether the noise level exceeds 70~80dB,
and the time and frequency of exposure to such noises.
Whether a worker has to travel from
one location to another with a time difference of five hours or more,
and the amount of such differences and the frequency of exposure to such
Work with mental stress
[Daily work subject to mental stress]
Work volume, length of time involved
in such work, worker experience and adaptive capabilities, and support
provided by the company
[Irregular work causing mental stress
during the period of time close to the appearance of a disease]
Severity of such irregular work (accidents or disasters) and extent of the