Japan’s Karoshi Line: What 80 and 100 Hours Mean and How to Seek Help
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Last Updated:
Category: Work Styles
Authors: Shusaku Yosa
The term karoshi line is commonly used in Japan when discussing the health effects of excessive work. The often-cited figures of 80 and 100 hours per month relate mainly to workers’ compensation criteria for brain and heart diseases. They are not an allowance for working safely up to those amounts.
If your hours are increasing, record your actual work and changes in your health, then seek help to reduce the workload. This article distinguishes compensation assessment, overtime limits, and physician interviews for employees working long hours.
What the 80-hour and 100-hour figures assess
Under the Ministry of Health, Labour and Welfare’s criteria for brain and heart diseases, a strong relationship between work and disease onset is assessed where overtime is approximately 100 hours in the month before onset, or exceeds a monthly average of 80 hours over a period of two to six months before onset.
For these criteria, overtime means work exceeding 40 hours per week. This may differ from time beyond your contractual schedule or the overtime figure on a payslip. Review actual working hours, including work on days off.
Hours alone do not automatically determine recognition. The disease and the workload are assessed together. Hours close to the cited figures can also be evaluated alongside factors such as short intervals between shifts, irregular schedules, and business travel. Short-term excessive workloads and extraordinary events have separate assessments.
Overtime limits and physician interviews are different rules
Similar numbers appear in different systems, but their purposes and conditions differ.
System | What it concerns | Common misunderstanding |
|---|---|---|
Compensation for brain and heart diseases | Assessment of workload before disease onset | Exceeding a figure guarantees recognition, or staying below it guarantees safety |
Overtime limits | The general limits start at 45 hours per month and 360 hours per year, with additional conditions for special clauses | An employer can freely require 100 hours |
Physician interviews for long working hours | For ordinary employees, more than 80 hours, accumulated fatigue, and an employee request are relevant conditions | You must wait until 80 hours to seek health advice |
Under the general overtime rules, even a special clause for temporary exceptional circumstances is subject to an annual limit of 720 overtime hours. Overtime plus holiday work must remain below 100 hours in any single month and at or below an average of 80 hours over each period of two to six months. Overtime above 45 hours is limited to six months per year. Statutory holiday work is excluded from the annual 720-hour limit but included in the single-month and multiple-month totals.
These are the general rules. Occupations such as motor vehicle driving and medical practice have special provisions. Check what applies to your work. For pay classifications, see our guide to statutory overtime and premium pay.
Record work and recovery, not just the company total
Prepare a daily record of the following:
- Start and finish times, and breaks during which you actually stopped working.
- Work on days off, work taken home, and required responses outside normal hours.
- Differences between recorded and actual hours, with dates and reasons.
- Sleep, fatigue, changes in health, and dates of medical visits or consultations.
- When the workload increased, deadlines, staffing shortages, and role changes.
Remote work and a fixed overtime allowance do not remove the need to establish actual hours. For the pay arrangement, see our fixed overtime pay guide.
You do not need to remove confidential business or customer information to keep a record. Focus on your own work history and ask the consultation service about handling documents if you are unsure.
Ask for specific changes to the workload
If you are concerned about your health, consult a medical professional without waiting for the hours calculation or company approval. When speaking to a manager or HR, describe the recent work and the changes you need.
For example: “My hours have been long over the past two months, and I remain tired after sleeping. Several deadlines fall this week. Can we transfer part of my work and stop after-hours responses? Please also tell me how to consult the occupational physician.”
For ordinary employees whose work exceeding 40 hours per week totals more than 80 hours in a month and who have accumulated fatigue, the employer must arrange a physician interview when the employee requests one. Different requirements also apply to employees engaged in research and development and those covered by the highly skilled professional system.
After the interview, check workplace measures based on the physician’s opinion, such as shorter hours or reassigned duties. Record the consultation date, response, work to be changed, and review date so you can check whether the load actually fell.
If the workplace does not improve
A Labor Standards Inspection Office can advise on working hours and wages. A General Labor Consultation Corner handles a broad range of employment concerns. An inspection office can also explain compensation procedures and documents if illness may be related to work. An employer’s refusal to provide certification does not itself prevent a claim.
If you are considering leave or a job change, first protect your current health and living arrangements. When comparing employers, ask about peak hours, staffing cover, after-hours messages, time-record corrections, and health consultation services. Our Labor Standards Act overview explains the basic workplace checks.
Frequently asked questions
Is it safe to continue working below 80 hours despite feeling unwell?
An hours total cannot establish personal safety. If sleep or fatigue changes, seek medical or occupational health advice without waiting to cross a threshold.
Does exceeding 100 hours guarantee compensation recognition?
No. These figures mainly concern brain and heart disease criteria. The disease, period before onset, and other workload factors also matter. Mental disorders have separate compensation criteria.
Does fixed overtime pay give the employer a right to require long hours?
No. It is a pay arrangement and does not remove limits on working hours or health protection duties.
Use the karoshi figures as a reason to examine actual work and seek a lower workload, rather than as a countdown to a personal limit.
Sources: MHLW: compensation criteria for brain and heart diseases / MHLW: four points in the revised criteria / Aomori Labour Bureau: overtime limits / MHLW: notice on physician interviews
