Smokers are at a greater risk of a second stroke than people who have never smoked, even though they have managed to stop after the first stroke, a Chinese study suggests.
Smoking has been associated with an increased risk of cardiovascular disease and serious cardiac events such as heart attacks and strokes. But the new study sheds light on how smoking affects the risk of a second stroke in patients who have had one.
Among the 3,069 stroke survivors in the study, 1,475, or 48 percent, were current smokers and another nine percent were former smokers.
Among current smokers, 908, or 62 percent, were able to quit within a few months after the stroke.
As expected, smokers had a greater risk of a second stroke than people who never smoked, even though they were able to stop after the first stroke. However, smokers who stopped after the first stroke were 29 percent less likely to take a second than people who smoked.
"Smoking after a stroke has the same effects on the body before the first stroke," said Allan Hackshaw, a researcher at University College London in the UK who did not participate in the study.
"This can lead to problems with blood flow in the brain and contribute to clots in the blood vessels – and any one of them increases the chance of having a stroke," Hackshaw said in an e-mail. "Cutting would reduce the risk a bit, but the study shows that giving up completely has a large reduction in the risk of a second stroke."
All patients in the study survived for at least three months after a stroke.
The risk of the smoker repeating an attack increased with the number of daily cigarettes they smoked.
Compared to nonsmokers, current smokers who had up to 20 cigarettes per day were 68% more likely to have a new effusion, while the risk was almost triple for smokers who had more than 40 cigarettes per day.
Current smokers tend to be younger and less likely to have conditions such as high blood pressure, heart rhythm disturbances or coronary heart disease than nonsmokers. They were also more likely to be heavy drinkers than non-smokers.
The study was not a controlled experiment designed to prove whether or how smoking causes repetitive effusions.
One limitation of the study is the potential for smokers to go through other lifestyle changes when they give up – such as improving eating and exercise habits – that have helped reduce the risk of stroke, Dr. Gelin Xu of Nanjing Medical University in Jiangsu, China , and colleagues in the Journal of the American Heart Association. Xu did not respond to requests for comment.
Even so, the results add up to a large body of evidence linking smoking cessation to a reduced risk of stroke, and continued to smoke at high risk of stroke, said Dr. Michael Hill of the Cumming School of Medicine at the University of Calgary, In Canada.
"Smoking is the worst thing you can do for your health," said Hill, who was not involved in the study by e-mail. "Yes, giving up helps a lot, but it's difficult because it's addictive."