The US researchers analysed the responses of almost 11,000 Americans to the annual National Longitudinal Survey of Youth. The survey included questions about employment history, work schedules, and sick leave, covering the period between 1987 and 2000.
In total, 110,236 job records were analysed, and 5,139 work related injuries and illnesses occurred. Over half of these were in jobs with extended working hours or overtime. In the USA, up to a third of overtime is compulsory.
After adjusting for age, gender, type of industry and job, employees working overtime were 61% more likely to sustain a work related injury or illness than employees who did not work overtime.
Working at least 12 hours a day was associated with a 37% increased risk of injury or illness, while working at least 60 hours a week was associated with a 23% increased risk, compared with those who worked fewer hours.
The more hours worked, the greater was the risk. But lengthy commutes had no impact on the injury/illness rate.
Further analysis indicated that the increased risks were not merely the result of demanding work schedules being concentrated in inherently "riskier" industries or jobs.
The authors say their findings back up the theory that long working hours indirectly precipitate workplace accidents by inducing fatigue and stress. And they support government initiatives, such as those espoused by the European Union, to cut working hours.