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Feb. 17, 2006
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Abstract P380
This news release contains updated data from the abstract.
American Stroke Association meeting report:
Amount of past smoking may affect stroke risk
KISSIMMEE, Fla., Feb. 17 – Your risk of stroke may hinge more on how much you smoked in the past than how long ago you quit, according to a small study reported today at the American Stroke Association’s International Stroke Conference 2006.
Previous studies have indicated that five to 15 years after quitting, former smokers’ excess stroke risk declined to the same level as that of people who have never smoked. However, those earlier studies generally considered only how much time had passed and did not consider how long or how many packs of cigarettes the person had smoked, researchers said.
Researchers in Baltimore and Cleveland now say that the total volume of smoking has a greater influence on stroke risk than the number of years of smoking cessation.
“The effect of back years of smoking was almost double, compared to the duration of smoking cessation history,” said Sachin Agarwal, M.D., M.P.H., a post-doctoral fellow in cardiovascular medicine at the Johns Hopkins Hospital in Baltimore, Md. “It does matter how early you quit smoking, but it matters even more how much you were smoking at that time.”
Researchers used magnetic resonance imaging (MRI) to compare the thickness of the carotid (neck) arteries in former smokers and people who had never smoked. Many strokes occur when one or both of the neck arteries narrow because of plaque build up and a clot plugs the artery and shuts off blood flow to the brain. Thickening of the carotid walls precedes the accumulation of plaque and contributes to increased stroke risk. Thickness of the aorta, the main artery that carries blood from the heart to the body, also was determined by MRI.
The study involved 42 men and women – 27 former smokers and 15 never smokers whose average age was 73 years. The former smokers had stopped smoking an average of 30 years previously, and their average smoking exposure was 20 pack-years (derived from the number of years smoked and the number of packs of cigarettes smoked daily).
Further, Agarwal and his associates divided the former smokers into four groups, according to their pack-years of smoking and duration of smoking cessation:
- Group 1: those who smoked 20 pack-years or less and more than 15 years smoking cessation;
- Group 2: those who smoked 20 pack-years or less and 15 years or less of smoking cessation;
- Group 3: those who smoked 20 pack-years and more than 15 years of smoking cessation;
- Group 4: those who smoked more than 20 pack-years and smoking cessation of 15 years or less.
Comparing all the former smokers with the never smokers, MRI imaging showed that former smokers’ aortic walls were 1.13 cubic centimeters (cm3) thicker than that of the never smokers – a significant statistical difference.
Differences in aortic wall volume between former smokers and never smokers increased progressively from former smokers in Group 1 with a difference of 0.99 cm3, to Group 2 with 1.3 cm3, to smokers in Group 3 with 1.73 cm3, and through Group 4 with 2.02 cm3.
Researchers found a similar pattern was seen in the carotid arteries. The carotid wall thickness of former smokers was 0.14 cubic millimeters (mm3) greater than that of never smokers. The difference in carotid wall thickness from never smokers increased progressively from 0.108 mm3 in Group 1 (shorter smoking history/longer duration of smoking cessation) to 0.27 mm3 in Group 4 (longer smoking history/shorter duration of cessation).
“We saw there was a strong and direct relationship between arterial wall thickness and increasing levels of risks of former smoking,” Agarwal said.
The associations between smoking and arterial wall thickness remained statistically significant after adjusting for age, gender, history of hypertension, diabetes, amount of alcohol intake, LDL cholesterol and E-Selectin levels.
Joao A.C. Lima, M.D., M.B.A., the principal investigator of the study and an associate professor of cardiology and radiology and director of non-invasive imaging at Johns Hopkins, noted that the study’s small sample size may have been a limitation of the study.
“However, the results were based on MRI technique using in vivo high-resolution multi-contrast and contrast-enhanced techniques which have the advantages of providing increased vessel coverage plus the tomographic orientation of MRI enables the full cross-sectional view of the vessel wall,” he said. “We believe the high accuracy and reproducibility of measurements may have compensated for the relative small groups of patients within each category.”
Agarwal said the message is clear: “Smokers should quit as soon as possible.”
American Stroke Association’s Advisory Committee chair Ralph Sacco, M.D., agreed that the best solution is to never start smoking or to quit right now.
“This study did not focus on stroke risk, but rather on evidence of subclinical disease – the thickness of carotid artery walls and or aorta walls,” said Sacco. “It is clear that any smoking can have a damaging influence on our arteries. However, outcome studies have shown that quitters can reduce their risk of stroke. Despite the presence of artery damage, quitting smoking may still reduce the chance of these arterial lesions ever causing stroke.”
Agarwals’ other co-authors were Amy E. Spooner,M.D.; Milind Y. Desai,M.D.; and David A. Bluemke, M.D., Ph.D. The National Institute on Aging sponsored the research.
Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.
NR06-1021 (ISC06/Agarwal)
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