Quitting smoking is always the right choice for health, but it won't necessarily protect former heavy smokers from strokes, HealthDay News reported Feb. 17.

Some studies have suggested that people who quit smoking could lower their risk of cardiovascular disease to that of people who never smoked. But researchers say that may not be true of people who smoked heavily before quitting.

"Even after years of smoking cessation, levels of atherosclerosis [hardening of the arteries] are significantly higher in former smokers compared with never-smokers," said Sachin Agarwal, a researcher at Johns Hopkins Hospital in Baltimore who led a new study on the long-term impact of smoking. "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."

Researchers reached their conclusions after taking detailed MRI scans of former smokers, some who had quit smoking 30 years ago. They found that the aortas of former smokers were significantly thicker than those who never had smoked. And the more cigarettes the smokers had consumed in their lifetime, the thicker their arteries, regardless of how long they had been abstinent.

"The amount of smoking you do now is going to affect your vessels and atherosclerosis much more than you think," Agarwal said.

The study was presented at the recent annual meeting of the American Stroke Association.