Stroke risk remains higher in ex-smokers

While quitting smoking is always a good idea, a new study suggests it's how much people smoke, not how long ago they quit, that really determines their long-term risk of stroke.

The study also challenges the conventional wisdom that an ex-smoker's long-term cardiovascular risk declines throughout the years, until it equals that of nonsmokers.

Earlier studies suggested that five to 15 years after quitting, an ex-smoker's risk of stroke falls to the same level as if they had never smoked. But those studies failed to consider how many packs of cigarettes a person smoked per day, the researchers explained.

"Even after years of smoking cessation, levels of atherosclerosis [hardening of the arteries] are significantly higher in former smokers compared with never-smokers," noted lead researcher Dr. Sachin Agarwal, a post-doctoral fellow in cardiovascular medicine at Johns Hopkins Hospital in Baltimore.

"We found that the number of packs of cigarettes smoked were almost twice as important in predicting the levels of atherosclerosis, compared with the years of cessation," he added.

The findings were presented Friday at the American Stroke Association's annual stroke conference in Kissimmee, Fla.

In their study, Agarwal and his colleagues collected data on 42 men and women, averaging 73 years of age. Twenty-seven of the participants were former smokers, and 15 had never smoked.

The ex-smokers had stopped smoking an average of 30 years prior to the study. They had smoked for an average of 20 "pack-years," a measurement that includes both the number of years the person smoked and the number of packs of cigarettes he or she smoked daily. The ex-smokers were broken into four groups, depending on how much they had smoked daily.

The researchers also took detailed MRI images of the wall of each person's aorta --- the major artery leading from the heart.

The imaging showed that the wall of the aorta of former smokers was significantly thicker than that of never-smokers, despite decades having elapsed since the ex-smokers' last cigarette. The more a former smoker had smoked, the greater the difference in the thickness of the aorta wall, the researchers found.

The finding shouldn't change the standard advice on smoking, Agarwal said. "The first thing is to quit," he said. "It's the best thing you can do for yourself."

The findings also suggest that current smokers should at least try to smoke less, since how much you smoke may be as or more damaging than the number of years spent smoking. "The amount of smoking you do now is going to affect your vessels and atherosclerosis much more than you think," he said.

One expert thinks that the study is too small to be definitive, however.

"The epidemiological evidence that your [stroke] risk stops was shown on a much larger study," noted Dr. Thomas M. Hemmen, an assistant professor of neurology at the University of California, San Diego. And he said it's already "a well-known fact that smoking causes atherosclerosis."

Another expert said he wasn't surprised by the findings.

"This is yet another study which demonstrates the deleterious effects of smoking," said Dr. Roger E. Kelley, a professor of neurology at Louisiana State University. "It is also not surprising that there is a dose effect, with the greater the exposure to smoking, the greater the arterial wall thickness."

"I am not particularly surprised that discontinuation of smoking did not have a reversible effect on the arterial wall thickness," Kelley said. "This would require that the vessel wall reparative process in some way reverses the atherosclerosis once the contribution from smoking is removed. This either doesn't happen, or it takes longer than the duration of this study factored in." -- Health Day