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Clot, inflammation factors higher in smokers

By Linda Carroll

Last Updated: 2003-06-06 16:37:09 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Cigarette smokers have higher blood levels of three clotting and inflammation factors that have been linked to a greater risk of heart disease, a new study shows.

A heart expert unaffiliated with the study said that the new results may help explain why smokers are at higher risk of having heart attacks -- and why that risk diminishes fairly quickly after a smoker quits.

"It's been clear for a while that smoking is a risk factor for heart disease," Dr. Daniel J. Rader, director of preventive cardiology at the University of Pennsylvania School of Medicine in Philadelphia, said in an interview. "But there's still a big question as to why smoking is a risk factor."

In the new study, which included more than 17,000 smokers, non-smokers and former smokers, current smokers had the highest levels of C-reactive protein, fibrinogen and homocysteine.

Former smokers had only slightly elevated levels of all three markers compared to non-smokers, according to the report published this week in the Annals of Internal Medicine.

The study, conducted by Dr. Lydia A. Bazzano, of the Tulane University School of Public Health and Tropical Medicine in New Orleans, and colleagues, included participants in the National Health and Nutrition Examination Study (NHANES).

The study may help explain why the risk of heart disease and heart attack go down quickly after a smoker kicks the habit, Rader said.

"If smoking promoted atherosclerosis, you would expect that if someone smoked for 20 years that the elevated risk would still persist," Rader explained. "So that suggests that the impact of smoking is not so much on plaque buildup itself but on factors that promote plaque rupture."

A heart attack occurs when fatty plaques inside arteries rupture and the body forms a clot to help repair the damage, Rader explained. If any of the clots make their way to the heart's arteries, they can block blood flow to the organ.

Fibrinogen and C-reactive protein are both related to inflammation, Rader said.

"And that's definitely a key component of plaque rupture," he added. "Fibrinogen and homocysteine are key components in the development of (clots)."

There are other, more important, markers of clots, Rader noted. And, he added, "It would have been a more complete study if those other markers had also been measured."

Still, the new study underscores the importance of quitting smoking to protect the heart, Rader said.

"It's a little known fact that in ex-smokers the risk of heart disease goes back to baseline within about two years, as compared to lung cancer, for which the markedly increased risk remains at least a couple of decades after a smoker quits," he said.

Copyright 2002 Reuters.