People who work for more than 10 hours a day may have a significant risk of stroke, a study warns.
Researchers reviewed data from a French population-based study group started in 2012, on 143,592 participants.
Cardiovascular risk factors and previous stroke occurrences were noted from separate medical interviews.
The study, published in the journal Stroke, found that overall 1,224 of the participants suffered strokes while 29 per cent or 42,542 reported working long hours.
As many as 10 per cent or 14,481 reported working long hours for 10 years or more.
The participants working long hours had a 29 per cent greater risk of stroke, and those working long hours for 10 years or more had a 45 per cent greater risk of stroke.
Long work hours were defined as working more than 10 hours for at least 50 days per year.
Part-time workers and those who suffered strokes before working long hours were excluded from the study.
"The association between 10 years of long work hours and stroke seemed stronger for people under the age of 50," said Alexis Descatha, a researcher at Paris Hospital and Angers University in France.
"This was unexpected. Further research is needed to explore this finding," Descatha said.
"I would also emphasise that many healthcare providers work much more than the definition of long working hours and may also be at higher risk of stroke," said Descatha, also associated with the French National Institute of Health and Medical Research (Inserm).
Previous studies noted a smaller effect of long work hours among business owners, CEOs, farmers, professionals and managers.
Researchers noted that it might be because those groups generally have greater decision latitude than other workers.
Other studies have suggested that irregular shifts, night work and job strain may be responsible for unhealthy work conditions.