Working long hours can greatly increase the risk of suffering injury or illness, a study says.
Workers who do overtime were 61% more likely to become hurt or ill, once factors such as age and gender were taken into account.
And working more than 12 hours a day raised the risk by more than a third, the University of Massachusetts found.
A 60-hour week carried a 23% greater risk, the study of US records from 110,236 employment periods found.
The study looked at data from 1987 to 2000. An employment period relates to the time a person spent at one firm. Counting this way meant some individuals might have been covered by the research more than once.
Report co-author Allard Dembe said risk was not necessarily associated with how hazardous the job was.
“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.
“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.”
And he said the findings, published in the Occupational and Environmental Health journal, supported initiative such as the 48-hour European Working Time Directive to cut the number of working hours.
From the records, researchers found 5,139 work-related injuries and illnesses, ranging from stress to cuts, burns and muscle injuries.
More than half of these injuries and illnesses occurred in jobs with extended working hours or overtime.
The researchers concluded that the more hours worked, the greater the risk of injury.
But they did not find that lengthy commutes to and from work had any impact on illness and injury.
In the UK 14% of the working population – 3.6m – work more than 48 hours a week.
Paul Sellers, a policy adviser at the Trade Union Congress, said the findings were unsurprising.
“It is clear that working long hours is not good for you. And what is important to realise that it is not fair on other people.
“If you are involved in an accident whether at work or because you are tired from work it can involve other people.
“In the UK the situation is gradually getting better, but employers need to realise it is in their interests not to push people into working long hours.
“Often it is the case of a workplace not being organised properly that people work long hours.”