Smokers have a higher risk of having a second stroke than people who have never smoked at all, even if they manage to quit after their first stroke, a study in China shows.
Smoking has long been associated with an increased risk of cardiovascular disease and serious heart events such as heart attacks and strokes. But this new study highlights how smoking affects the risk of second stroke in patients who have experienced it.
Among 3,069 stroke survivors in this study, 1,475, or 48 percent, were current smokers and the other nine percent were former smokers.
Among current smokers, 908, or 62 percent, managed to quit within a few months after their stroke.
As expected, smokers have a higher risk of having a second stroke than people who have never smoked at all, even if they manage to stop after their first stroke. However, smokers who quit after the first stroke were 29 percent less likely to experience a second smoker than people who continued to smoke.
"Smoking after a stroke has the same effect on the body as before the first stroke," said Allan Hackshaw, a researcher at University College London in England who was not involved in the study.
"This can cause problems with blood flow in the brain, and contribute to the formation of clots in blood vessels – and one of these increases the chance of stroke," Hackshaw said via email. "Cutting back will reduce the risk a little, but research shows that stopping completely has a large reduction in the risk of a second stroke."
All patients in the study survived for at least three months after the stroke.
The risk of smokers for recurrent strokes increases with the number of cigarettes smoked every day.
Compared to nonsmokers, current smokers who have 20 cigarettes per day are 68 percent more likely to experience recurrent strokes, while the risk is almost three times that for smokers who have more than 40 cigarettes a day.
Smokers today tend to be younger and tend to have conditions such as high blood pressure, heart rhythm disorders or coronary heart disease than nonsmokers. They are also more likely to be heavy drinkers than nonsmokers.
This study is not a controlled experiment designed to prove whether or how smoking causes recurrent strokes.
One limitation of this study is the potential for smokers to experience other lifestyle changes when they stop – such as increasing eating and exercise habits – that contribute to reducing the risk of stroke, Dr. Gelin Xu from Nanjing Medical University in Jiangsu, China, and colleagues noted in Journal of the American Heart Association. Xu did not respond to requests for comment.
Even so, the results add a large amount of evidence linking smoking cessation to a reduction in stroke risk, and continuing smoking with an increased 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," Hill, who was not involved in the study, said via email. "Yes, stopping helps a lot, but it's difficult because it's addictive."