A culture of long working hours increases the risk of injury and illness to workers, with the level of risk nothing to do with how hazardous the job is, researchers have concluded.
A U.S study, published in the journal Occupational and Environmental Medicine, surveyed almost 11,000 Americans on their employment history, work schedules, and sick leave, covering the period between 1987 and 2000.
In total, 110,236 job records were analysed, and it was found that 5,139 work-related injuries and illnesses occurred.
More than half of these were in jobs with extended working hours or overtime. In the U.S, up to a third of overtime is compulsory.
After adjusting for age, gender, type of industry and job, employees working overtime were 61 per cent more likely to sustain a work-related injury or illness than employees who did not work overtime, the researchers said.
Working at least 12 hours a day was associated with a 37 per cent increased risk of injury or illness, while working at least 60 hours a week was associated with a 23 per cent 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, the study also found.
Increased risks were not merely the result of demanding work schedules being concentrated in inherently "riskier" industries or jobs, it added.
The study also argued that its findings backed up the theory that long working hours indirectly precipitate workplace accidents by inducing fatigue and stress.
Government-led initiatives to cut working hours, such as the Working Time Directive in Europe, should therefore be applauded, it argued.
"The results of this study suggest that jobs with long working hours are not more risky merely because they are concentrated in inherently hazardous industries or occupations," said Allard Dembe, co-author of the study.
"Our findings are consistent with the hypothesis that long working hours indirectly precipitate workplace accidents through a causal process, for instance, by inducing fatigue or stress in affected workers."