Smoking appears to reduce the ability of the arteries that feed the heart muscle to respond to stress, according to a report.
Researchers at the University of California, Los Angeles, also suggest that the longer a person smokes, the more severe the effect on the coronary arteries' ability to widen under stressful conditions. The widening of these arteries increases blood flow to the heart when required, such as during exercise.
The study's authors, led by Dr. Roxana Campisi, studied a group of longtime smokers and a comparison group of nonsmokers. The smoking group included 13 men and 3 women who had been smoking for between 11 and 39 years. The comparison group included 10 men and 7 women. None of the men or women in the study had high blood pressure, high blood cholesterol levels, or other signs of heart disease, the researchers report in the current issue of Circulation: Journal of the American Heart Association.
The researchers gave both groups a series of tests to determine how well their coronary arteries dilated or widened to demands for increased blood flow. In situations in which the heart needs more blood -- during strenuous exercise, for instance -- healthy blood vessels will widen to increase blood flow, thus meeting an increased demand for oxygen in the tissues.
Test results showed that the smokers' arteries did not adapt as well, or dilate as much, as the nonsmokers' arteries. On average, the smokers had about 14% less blood flow to the heart during the tests than the nonsmokers did.
And the longer an individual had been smoking, the more marked the reduction in blood flow through the coronary arteries under stress, the researchers found.
"The longer you smoke, the more abnormal the blood flow," said Dr. Johannes Czernin, a co-author of the study. "Now we want to know how long it takes after a person quits smoking before normal blood vessel function is regained," he noted in a statement issued by the Association.
These results suggest that the smokers -- though apparently "healthy" -- had damage to the lining or endothelium of their arteries, and that this damage may precede obvious signs of arterial disease, the researchers conclude. Previous research suggests that smoking can damage the endothelium. And studies suggest that endothelial damage can contribute to the development of heart disease.
"(T)he abnormal blood flow response ...in the long-term smokers observed in the current study most likely resulted from coronary endothelial dysfunction," Campisi and co-authors write.
The researchers also found that smokers with a lower ratio of HDL (or "good cholesterol") to LDL (commonly known as "bad cholesterol") also had less adaptive blood vessels. These findings support those of earlier studies that suggest low HDL/LDL ratios can play a role in endothelial damage as well, Campisi and colleagues write.
SOURCE: Circulation 1998;98:119-125.