Those who work long hours are more likely to have a stroke, according to analysis published in the Lancet medical journal.
The data, gleaned from more than 500,000 people from the US, Europe and Australia showed the chance of a stroke increased as working hours crept past the traditional nine-to-five. Even the odd extra hour-or-two could have a detrimental affect.
Working 41 to 48 hours a week was associated with a 10% risk increase, which rose higher as the hours mounted up.
Working 49 to 54 hours pushed up the chances of a stroke by 27% and 55 or more hours raised the risk by a third.
The hardest grafters also experienced a more modest 13% increased risk of heart disease.
Lead author Professor Mika Kivimaki, from University College London, said:
Why working long hours has such an impact on stroke risk remains unclear, however.
The scientists suggest that as well as stress, unhealthy behaviours such as physical inactivity and high alcohol consumption might be involved.