Smoking more than 20 cigarettes a day almost triples the chances of suffering a potentially fatal brain haemorrhage, research has shown.
Quitting reduces the danger but heavy smokers who give up tobacco are still twice as much at risk as people who have never smoked.
Researchers in Korea investigated 426 cases of subarachnoid haemorrhage (SAH) between 2002 and 2004.
Patients were compared with a group of 426 people matched for age and sex who had not experienced a brain bleed.
An SAH occurs when a bulge in a weakened artery, called an aneurysm, bursts in the brain.
The chances of surviving are only about 50%, and victims who live often face a lifetime of disability.
Study participants who smoked were more likely to have suffered an SAH than non-smokers, scientists found.
The more people smoked, the more at risk they were. After adjusting for other factors such as salt intake, weight and family history of diabetes, smokers were on average 2.84 times more likely to have a brain haemorrhage as non-smokers.
Giving up tobacco for at least five years dramatically reduced the overall risk to 59%. But people with a history of heavy smoking - defined as smoking 20 or more cigarettes a day - were still 2.3 times more likely to have an SAH than those who had never smoked.
The research team, led by Dr Chi Kyung Kim, from Seoul National University Hospital, wrote in the Journal of Neurology, Neurosurgery and Psychiatry: “To forestall tragic SAH events, our results call for more global and vigorous efforts for people to stop smoking.”